Rational Treatment Method for Spent Nuclear Fuel

Abstract

To provide a rational high level radioactive waste processing method for converting an unnecessary radioactive nuclide which is generated in spent nuclear fuel into a short life nuclide or stable nuclide, increasing weight of reusable nuclides, and reducing the amount of waste which is vitrified.SOLUTION: A rational high level radioactive waste processing method uses: a gas tank for collecting a gas nuclide which is generated immediately after nuclear fuel extraction; a soluble substance tank for collecting nuclides which are soluble in a nitric acid after collection processing such as a PUREX method or the like; and an insoluble substance tank for collecting nuclides which are not easily solved in a nitric acid and insoluble nuclides after the collection processing. In the gas tank, after storage for a regulated period, only iodine is irradiated with thermal neutrons once, only the soluble nuclides in the soluble substance tank and the insoluble nuclides and the nuclides which are not easily solved in the insoluble substance tank are irradiated with cold neutrons, and radiation in storage for a regulated period and storage are repeated multiple times, then oxides generated in the respective tanks are converted into chlorides whose boiling points are low, then elements are separated by a fractional distillation method using a difference of the boiling points, and if necessary, isotopes are separated using a gas centrifugal separation method, for collecting radioactive nuclides and stable nuclides reusable as resources, and reducing the amount of waste nuclides being vitrified.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a technology for treating high-level radioactive waste by fission products.

Background Art

[0002] In a nuclear power plant with a capacity of 1 million kW, about 23 tons of nuclear fuel is used annually with 5% enriched uranium fuel. The fission products (FP) generated from the spent nuclear fuel vary in nuclide and generation amount depending on the ratio of U235, burnup, operating conditions, irradiation time, etc. Generally, it is said that the fission products generated from 1 ton of nuclear fuel are 2 to 5%.

[0003] These fission products become high-level radioactive liquid waste (HALW) after recovering actinides such as uranium and plutonium by reprocessing the spent nuclear fuel based on the PUREX (Plutonium and Uranium Recovery by Extraction) method. (For actinide removal, there is Patent Document 1, etc.)

[0004] This high-level radioactive liquid waste is concentrated to reduce its volume, melted into glass, and solidified in a stainless steel container (canister) (glass solidified body). Since this glass solidified body maintains a high temperature due to the decay of the internal radioactive substances, it is stored in an interim storage facility for about 30 to 50 years until the radioactive substances decrease and the temperature drops. Finally, this glass solidified body is disposed (stratified disposal) in a stable stratum more than 300 meters deep underground.

[0005] In such a treatment method, the amount of vitrified waste increases, and issues such as securing storage space and managing the vitrified waste arise. In particular, securing storage space is an urgent issue. Therefore, elements and radionuclides in high-level waste are grouped according to half-life, chemical properties of the elements, purpose of use, etc. For long-lived nuclides, nuclear reactions are induced by neutron irradiation or the like to convert them into short-lived or non-radioactive nuclides (nuclear conversion technology), and further, methods of utilizing useful elements and nuclides (resource recovery of high-level waste) are being studied. (Non-Patent Document 1, etc.)

[0006] In nuclear conversion technology, there are reported examples of irradiating long-lived fission products with neutrons, charged particle beams, positrons, etc. to cause nuclide conversion, but these are only for specific radionuclides and do not relate to the entire high-level radioactive waste. (Patent Documents 2, 3, 4)

[0007] Methods have been proposed for selectively separating and recovering platinum group elements, technetium, tellurium, and selenium from nitric acid dissolution solutions handled in reprocessing plants for spent nuclear fuel or radioactive process waste liquids generated in the process with high recovery rates, but these relate to recovery for reuse and not to vitrified waste. (Patent Document 5)

[0008] In a method for treating radioactive waste, high-energy neutrons generated by an accelerator are irradiated onto a group of isotope elements containing radionuclides among fission products in radioactive waste and having a common atomic number to cause inelastic scattering, and nuclide conversion is performed to reduce the mass number (number of neutrons) by 1 or 2 by means of (n,2n) reaction or (n,3n) reaction. Utilizing the fact that this differs based on the odd-even nature of the neutron separation energy of the isotope elements, a neutron energy band in which the reaction cross-sections of nuclides with different mass numbers differ by 10 times or more is selected, and the neutrons in this selected energy band are irradiated to reduce the mass number of the long-lived nuclides to be converted and convert them into short-lived nuclides or stable nuclides. A technique for extraction without isotope separation is disclosed. (Patent Document 6)

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Non-Patent Document

[0010]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0011] However, in a method for treating radioactive waste that utilizes the difference based on the parity of the neutron separation energy of the above-mentioned isotope elements, irradiates neutrons in a selected high-energy band to reduce the mass number of a long-lived radionuclide to be converted, and converts it into a short-lived radionuclide or a stable nuclide. Neutrons in high-energy bands with a reaction cross-section difference of 10 times or more are irradiated. Although the reaction cross-section of the nuclide that is not desired to be converted is less than one-tenth, an (n,2n) reaction may occur, and it is considered that radionuclides will remain, making it difficult to achieve complete separation of radionuclides and stable nuclides. Also, the elements targeted by the radioactive waste are 10 elements, and there is no description of radionuclides with a half-life of 10 10 years or more. Furthermore, there is no description of the generated weight or radioactivity of radionuclides, and there is no quantitative description.

[0012] The present invention aims to provide a reasonable method for treating fission products that converts unnecessary radionuclides into short-lived nuclides or stable nuclides for nuclides contained in high-level radioactive waste liquid remaining after removing actinides such as uranium and plutonium by reprocessing such as the PUREX method from spent nuclear fuel generated in nuclear power plants, and for nuclides contained in residues not contained in the waste liquid, reduces the weight of vitrification of radioactive waste, and recovers reusable radionuclides and stable nuclides as resources.

Means for Solving the Problems

[0013] The present invention provides a method for treating radioactive waste, which comprises a tank for collecting and storing gaseous nuclides generated immediately after removal from spent nuclear fuel (hereinafter referred to as the gas tank), and a storage tank for separating and collecting, after a specified time has elapsed following the recovery treatment of actinides such as uranium and plutonium, the nuclides soluble in nitric acid (hereinafter referred to as soluble nuclides) and the nuclides hardly soluble or insoluble in nitric acid (hereinafter referred to as hardly soluble nuclides) among the fission products excluding gaseous nuclides (hereinafter, the former of the storage tanks is referred to as the soluble material tank and the latter as the hardly soluble material tank). In this method, low-energy cold neutrons are irradiated onto these nuclides to change the mass number by neutron capture reaction for nuclide conversion. After neutron irradiation and after a specified time has elapsed, the method described in Claims 1 to 5 is used, and the radioactive waste is stored for a specified time and irradiated with neutrons a predetermined number of times.

[0014] In the method for treating the radioactive waste, after a specified time t including the cooling period has elapsed, the soluble nuclides in the soluble material tank are irradiated with cold neutrons for the first time. After storing for a specified time t 0 the gaseous nuclides generated by radioactive decay are transferred to the gas tank, and the generated hardly soluble nuclides are recovered using a solid-liquid separation device or the like into another storage tank (hardly soluble material tank A). Thereafter, after irradiating the soluble nuclides with cold neutrons Ni times, after storing for a specified time t 1 the gaseous nuclides generated by radioactive decay are collected in the gas tank, and the generated hardly soluble nuclides are recovered using a solid-liquid separation device or the like into the hardly soluble material tank A, and the hardly soluble nuclides are not irradiated with cold neutrons. i This is a method for treating radioactive waste.

[0015] In the method for treating the radioactive waste, after a predetermined time t 0 has elapsed, after irradiating the hardly soluble nuclides in the hardly soluble material tank with cold neutrons for the first time, a nitric acid solution with a specified concentration is introduced, and after storing for a specified time t' 1 if the generated gaseous nuclides are stable nuclides, they are exhausted, if they are radioactive nuclides, they are collected in the gas tank, the generated soluble nuclides are filtered together with the nitric acid solution and recovered into another storage tank (soluble material tank B). After the second irradiation of the hardly soluble nuclides with cold neutrons, the soluble nuclides recovered in the soluble material tank B and the nitric acid solution are refluxed to the hardly soluble material tank, and after storing for a specified time t 2Store it for a certain period of time. Subsequently, irradiate the sparingly soluble nuclide with cold neutrons Nj times. However, the soluble nuclide in the soluble substance tank B immediately before the Nj-th cold neutron irradiation is refluxed to the sparingly soluble substance tank together with the nitric acid solution after the Nj-th cold neutron irradiation, and the specified t j After storing for the specified t time, if the gas generated by radioactive decay is a stable nuclide, it is exhausted. If it is a radioactive nuclide, it is recovered in the gas tank. The soluble nuclide is recovered in the soluble substance tank B using a filtration device or the like, and the soluble nuclide is not irradiated with neutrons. This is a method for treating radioactive waste.

[0016] In the method for treating the radioactive waste, for the gaseous nuclides among the FPs, after the specified t 0 After the elapse of time, the gaseous nuclides generated in the soluble substance tank and the sparingly soluble substance tank are recovered. Immediately before the second cold neutron irradiation of the soluble nuclide, only iodine among the gas recovered from the soluble substance tank and the gas present in the gas tank is extracted and stored in the iodide tank, and only iodine is irradiated with neutrons once. At this time, the neutrons can be thermal neutrons. The gas generated in the iodide tank is recovered in the gas tank. If the gas generated in the sparingly soluble substance tank consists only of stable nuclides, it is not recovered in the gas tank. Subsequently, the gaseous nuclides are not irradiated with neutrons, and the solid nuclides generated by radioactive decay during this storage period are recovered in another storage tank (solid tank), and the solid nuclides are not irradiated with neutrons. This is a method for treating radioactive waste.

[0017] Repeat the cold neutron irradiation of the soluble substance tank and the sparingly soluble substance tank Ni and Nj times respectively. After leaving it for a certain period of about several years, the radioactive nuclides decay, and the generated solid nuclides are recovered in the soluble substance tank, the sparingly soluble substance tank A, the solid tank, and the sparingly soluble substance tank and the soluble substance tank B. The nuclides and nitric acid solution recovered in the first three are transferred to chloride tank 1 (equipped with a solidification device), and the nuclides and nitric acid solution recovered in the latter two are transferred to chloride tank 2 (equipped with a solidification device). By heating each to drive out the nitric acid, most of the nuclides become oxides.

[0018] Convert the oxides generated in the above chloride tank into chlorides with low boiling points. Charge the chlorides present in chloride tank 1 into the vaporization tank, heat them in ascending order of the boiling points of the chlorides, vaporize them in the rectifying column for each boiling point, fractionate them with a condenser, and take them out as chlorides. If there are only stable nuclides, recover them into the stable nuclide recovery tank through a cooling device. Nuclides that are only radioactive and isotopes that are a mixture of radioactive nuclides and stable nuclides are recovered into the vitrified nuclide recovery tank. Recover single radioactive nuclides that can be used as radioactive substances. For isotopes that are only two nuclides, namely radioactive nuclides that can be used as radioactive substances and stable nuclides that can be reused as resources, perform isotope separation using a gas centrifuge device that utilizes the mass difference used during uranium fuel production, and separate them into light nuclides with a small mass number and heavy nuclides with a large mass number, and recover them into the light nuclide recovery tank and the heavy nuclide recovery tank respectively. Next, treat chloride tank 2 in the same manner. By separately treating the nuclides generated in the soluble substance tank and the nuclides generated in the hardly soluble substance tank, the recovered weight of stable nuclides can be increased, and the weight of waste nuclides to be vitrified can be reduced.

Effect of the Invention

[0019] According to the present invention, it is possible to provide a reasonable method for treating fission products that converts unnecessary long-lived radioactive nuclides into short-lived nuclides or stable nuclides, reduces the weight of nuclides in the vitrified body of high-level radioactive waste, and recovers reusable radioactive nuclides and stable nuclides as resources for each nuclide or each element.

Brief Description of the Drawings

[0020]

Figure 1

Modes for Carrying Out the Invention

[0021] Hereinafter, embodiments of the present invention will be described with reference to Figure 1. The present invention is a method of irradiating a nuclide with low-energy cold neutrons having a large neutron capture cross-section of the nuclide, causing the nuclide to capture neutrons by a neutron capture reaction, and changing the mass number to perform nuclide conversion. The cold neutron source device decelerates neutrons generated from a neutron source using extremely low-temperature liquid hydrogen as a moderator, further decelerates them with liquid helium to convert them into cold neutrons, and includes a shutter for performing neutron irradiation for a certain period of time. Neutron irradiation opens the shutter for a time sufficient for the irradiated nuclide to be nuclide-converted. A nuclide with a large neutron capture cross-section captures neutrons and its mass number increases by 1. Further, if the neutron capture cross-section of the nuclide with a mass number increased by 1 is large, this nuclide also captures neutrons and its mass number increases by 2.

[0022] By neutron irradiation, a stable nuclide may be converted into a radioactive nuclide. Since the nuclide and weight generated by radioactive decay change depending on the number of neutron irradiations and the standing time after irradiation, it is necessary to optimize the number of neutron irradiations and the standing time so as to reduce the weight of the nuclide to be discarded and maximize the weight of the nuclide that can be recovered as a resource. This will be described in the examples.

[0023] (Treatment after standing for a certain period of time after spent nuclear fuel removal) Among the FPs generated from spent nuclear fuel removal, gaseous nuclides are recovered in a gas tank. Nuclides other than gaseous nuclides among the generated FPs are cooled for a certain period and then, after reprocessing such as the PUREX method, the remaining high-level radioactive waste contains soluble nuclides in a nitric acid solution and hardly soluble nuclides such as residues. 95% of the iodine generated in the nitric acid solution is recovered as a gas during uranium and plutonium recovery processing, and the rest remains as a residue in the nitric acid solution as silver iodide and palladium iodide. However, by adding iodine acid, etc., it can be recovered as a gas. Therefore, these gases generated in a certain period (t 0 time) are treated as the weight of the nuclides generated in the gas tank. [Reference 1; described at the end] Note that since carbon reacts with nitric acid and exists as CO 2 it is treated as a nuclide stored in the gas tank. [Reference 2: described at the end] However, the weight indicates only the value of carbon. The soluble nuclides and the insoluble nuclides are stored in a soluble substance tank and an insoluble substance tank respectively. The nitric acid solution containing nuclides soluble in nitric acid can be used as it is, or it can be denitrified first, and then a new nitric acid solution with a concentration of 4 - 6 mol / L is added. The nuclides soluble in nitric acid can be in the form of nitrates or oxides. The nitric acid solution containing the nuclides soluble in nitric acid is recovered in the soluble substance tank.

[0024] (Soluble substance tank) After the spent nuclear fuel is taken out, cooled, reprocessed, and after a certain period (t 0 hours), the nuclides in the nitric acid solution in the soluble substance tank from which the soluble nuclides have been recovered are irradiated with thermal neutrons for the first time, and stored for t 1 hours. After t 1 hours, the gaseous nuclides of helium, xenon, krypton, bromine, and iodine generated by radioactive decay with the soluble nuclides as parent nuclides are recovered in the gas tank. However, since bromine which is liquid at room temperature and iodine which is solid need to be recovered as gases, the soluble substance tank is heated if necessary. These gases are transferred to the gas tank by a vacuum pump or the like through a valve with backflow prevention. The insoluble nuclides such as germanium, zirconium, palladium, indium, and tin that are suspended or precipitated generated by radioactive decay are recovered in the attached insoluble substance tank A in the soluble substance tank through a solid-liquid separation device, and the filtered soluble nuclides are refluxed to the soluble substance tank together with the nitric acid solution. After t 1 hours, the nuclides in the soluble substance tank are irradiated with thermal neutrons for the second time and stored for t 2 hours. If necessary, the soluble substance tank is heated, the gaseous nuclides generated by radioactive decay during this storage period are recovered in the gas tank, the generated insoluble nuclides are recovered in the attached insoluble substance tank A in the soluble substance tank, and the nitric acid solution containing the soluble nuclides is refluxed to the soluble substance tank. Thereafter, the thermal neutrons are irradiated only to the soluble nuclides Ni times and stored for t i hours, and the gaseous nuclides generated by radioactive decay are recovered in the gas tank, the generated insoluble nuclides are recovered in the insoluble substance tank A, and the reflux of the nitric acid solution containing the soluble nuclides to the soluble substance tank is repeated. The insoluble nuclides generated during the storage period are not irradiated with thermal neutrons. This increases the recovered weight of the insoluble stable nuclides generated by decay. In addition, due to the heat generated during decay and heating, the nitric acid solution evaporates, so the required amount is replenished after thermal neutron irradiation to keep the liquid volume constant.

[0025] (Insoluble Material Tank) After the spent nuclear fuel is removed, cooled, reprocessed, and after a certain period (t 0 hours), the nuclides in the insoluble material tank from which the insoluble nuclides have been recovered are irradiated with thermal neutrons for the first time. Then, a nitric acid solution with a specified concentration is added to the insoluble material tank and stored for t 1 ’ hours. After t 1 ’ hours have passed, the insoluble nuclides decay with the parent nuclides The generated gaseous nuclides are collected in the gas tank. However, since bromine and iodine are released as gases, if necessary, the sparingly soluble substance tank is heated and collected in the gas tank by a vacuum pump or the like via a valve with backflow prevention. In addition, a nitric acid solution containing soluble nuclides such as boron, gallium, arsenic, selenium, silver, cadmium, tellurium, etc. generated by radioactive decay with the insoluble nuclides as the parent nuclides is filtered and recovered in the soluble material tank B attached to the insoluble material tank. After t 1 ’ hours have passed, the nuclides in the insoluble material tank are irradiated with thermal neutrons for the second time, and then the nitric acid solution containing the above-mentioned soluble nuclides and additional nitric acid solution are added and refluxed to the insoluble material tank for t 2 ’ hours of storage. The nuclides soluble in nitric acid and the nitric acid solution generated during this storage period are filtered immediately before the third thermal neutron irradiation and recovered in the soluble material tank B attached to the insoluble material tank The generated gaseous nuclides are collected and collected in the gas tank. . Thereafter, Since cold neutrons are not irradiated to nuclides soluble in nitric acid but only to sparingly soluble nuclides, N j After the Nth irradiation of cold neutrons to the sparingly soluble nuclides, the nitric acid solution obtained by filtering the nuclides soluble in nitric acid after the elapse of the time t of the previous cold neutron irradiation is refluxed from the soluble substance tank B to the sparingly soluble substance tank, j-1 and the nitric acid solution containing the soluble nuclides generated after storing for t hours is refluxed from the soluble substance tank B to the sparingly soluble substance tank, and the generated gaseous nuclides are collected in the gas tank. This is repeated N j times. j Repeat N times. The soluble nuclides generated during the storage period and Gaseous nuclides are not irradiated with thermal neutrons. This increases the recovered weight of the soluble stable nuclides generated by decay. Note that since the weight of the soluble nuclides generated after thermal neutron irradiation increases with the number of irradiations, it is necessary to increase the nitric acid solution as well.

[0026] (Gas Tank) The gaseous nuclides generated after leaving the spent nuclear fuel for a certain period (t 0 hours) are Combined with the gaseous nuclides generated in the soluble substance tank and the sparingly soluble substance tank recovered during this standing period , the gas tank is heated to sublime and vaporize bromine and iodine, and a cooling device provided at the upper part of the gas tank is used to cool the tray at the upper part of the gas tank to liquefy only iodine, which is then transferred to an iodide tank and irradiated with thermal neutrons for nuclide conversion. Since the neutron capture cross-section of iodine is large even for thermal neutrons, the neutrons can be irradiated with thermal neutrons. Standing period after thermal neutron irradiation The solid nuclides generated by radioactive decay are collected in the solid tank attached to the gas tank, In the solid tank and the generated gaseous nuclides are refluxed to the gas tank. The generated Solid nuclides are not irradiated with neutrons. Also, those generated in the iodide tank The gaseous nuclides are refluxed to the gas tank. After that, Synchronously with the cycle of cold neutron irradiation and storage in the soluble substance tank and the sparingly soluble substance tank, immediately before the cold neutron irradiation, the gases generated in both tanks are recovered, and after the last neutron irradiation, a nitric acid solution of a specified concentration is introduced after standing for a certain period (t S hours) for decay heat and temperature reduction, and the solid nuclides generated by the decay of the radioactive gas in the gas tank are recovered in the solid tank.

[0027] After repeatedly irradiating the soluble and insoluble tanks with cold neutrons Ni and Nj times respectively, and storing for a certain period of about several years, the solid nuclides generated by the decay of radioactive nuclides are recovered in the soluble tank, insoluble tank A, solid tank, and insoluble tank, soluble tank B. The nuclides and nitric acid solution recovered in the first three are transferred to chloride tank 1, and the nuclides and nitric acid solution recovered in the latter two are transferred to chloride tank 2. After heating each to drive out nitric acid, most nuclides become oxides. [Reference 3; described at the end]

[0028] The oxide isotopes generated from the above-mentioned first three and the latter two are separated by elements using the difference in boiling points, but the boiling points of these oxides are extremely high, so they are converted into chlorides with lower boiling points. The oxides transferred to chloride tanks 1 and 2 are converted into chlorides by injecting a hydrochloric acid solution of a specified concentration or chlorine gas. For nuclides that cannot be chlorinated with hydrochloric acid, if chlorine gas is used and carbon is added, chlorides are generated by heat treatment for several hours according to the following chemical formula. 2[M]On + nC + xCl 2 → 2[M]Clx + nCO 2 However, [M] represents a metal element, and boron, germanium, zirconium, niobium, rubidium, ruthenium, rhodium, palladium, thulium, hafnium are applicable. [Reference 4; described at the end]

[0029] The chlorides (60 nuclides in the example) mainly generated in the soluble substance tank existing in the chloride tank 1 are put into the vaporization tank, heated in ascending order of the boiling points of the chlorides, vaporized in the rectifying column for each boiling point, fractionated by the condenser, and taken out as chlorides. If they are stable nuclides and isotopes consisting only of stable nuclides, they are recovered into the nuclide recovery tank through the cooling device. Radionuclides, isotopes consisting only of radionuclides, or isotopes in which radionuclides and stable nuclides are mixed are recovered into the vitrified nuclide recovery tank. In addition, isotopes composed of two nuclides, a radionuclide that can be used as a radioactive substance and a stable nuclide that can be reused as a resource, are separated by a gas centrifuge device using the mass difference, separated into light nuclides with a small mass number and heavy nuclides with a large mass number, and recovered into the light nuclide recovery tank and the heavy nuclide recovery tank respectively.

[0030] Next, the chlorides (36 nuclides in the example) generated in the insoluble substance tank existing in the chloride tank 2 are put into the vaporization tank. Similarly to the above, they are heated in ascending order of the boiling points of the chlorides, vaporized in the rectifying column for each boiling point, fractionated by the condenser, and taken out as chlorides. If they are stable nuclides and isotopes consisting only of stable nuclides, they are recovered into the nuclide recovery tank through the cooling device. Radionuclides, isotopes consisting only of radionuclides, or isotopes in which radionuclides and stable nuclides are mixed are recovered into the vitrified nuclide recovery tank. Details are described in the example. Since the nuclides generated in the soluble substance tank and the insoluble substance tank are processed separately, the weight of the waste to be vitrified can be reduced.

[0031] In the gas tank, bromine and iodine exist, and both are stable nuclides and can be recovered as a liquid and a solid respectively at room temperature. For gaseous nuclides with a boiling point of 0 °C or lower, the weight of the radionuclide decreases, the weight of the stable nuclide increases, and the ratio of the radioactive gas to be discarded decreases slightly. The radionuclide iodine-129 is nuclide-converted into stable xenon-130.

[0032] Before describing the example, the definitions of the terms related to the present invention will be explained. The FPs generated from the spent nuclear fuel used in nuclear power generation decay by radioactive decay. These nuclides are shown in the order of atomic number, element symbol, and mass number, and the decay mode and half-life are shown in parentheses. When there are two decay modes, the branching ratio is expressed in %. The unit of the half-life is represented by seconds: s, minutes: m, hours: h, days: d, years: y. Note that 1 year is calculated as 365 days. The decay modes include α decay, β decay, γ decay, etc. In α decay, a helium nucleus (α particle) is emitted from the atomic nucleus, and the atomic number decreases by 2 and the mass number decreases by 4 to form an atom. In β decay, there are three types of decays. In one type of β decay, one electron is emitted from a neutron in the atomic nucleus, one neutron is converted into a proton, and the atomic number increases by 1 (hereinafter referred to as β decay). In another type of decay, a proton in the atomic nucleus emits a positron and is converted into a neutron, and the atomic number decreases by 1 (hereinafter referred to as ecβ+ decay or ε decay). In yet another type of decay, an electron outside the nucleus is captured by the nucleus, one proton is converted into a neutron, and the atomic number decreases by 1 (hereinafter referred to as ec decay). In all cases, electrons (β particles) are emitted. Furthermore, there is double β decay in which β decay occurs almost simultaneously. In this decay, two neutrons become protons, so the atomic number increases by 2 (hereinafter referred to as 2β decay). In any decay, the mass number does not change. In γ decay, when an excited atomic nucleus transitions to the ground state, the excess energy is radiated as γ rays, and the atomic number and mass number do not change. In nuclear isomer transition (hereinafter referred to as IT decay) in which the daughter nuclide in the excited state generated by decay emits γ rays and decays to the ground state, neither the atomic number nor the mass number changes. Nuclides with an m attached to the mass number are nuclear isomers. Here, the decay mode, branching ratio, and half-life were based on data from the IAEA. [Data citation source 1; described at the end] The order of decay changes from a nuclide with a higher nuclear energy level to a nuclide with a lower nuclear energy level. This energy level is based on data from the Mass Chain Chart of Nuclides in the IAEA NDS.

[0033] The time it takes for a certain nuclide to decay until its weight becomes half in radioactive decay is called the half-life τ, and the relationship with the decay constant λ is τ = ln(2) / λ [ln(2) is the natural logarithm of 2]. The radioactivity per gram of a nuclide is called the specific radioactivity S R and, if the Avogadro constant is N A and the mass number is Z, then S R = λ×N A / Z, and the unit is Bq / g. The degree of reduction of radioactivity is represented by the 0.1 Bq arrival time T 0.1 and, if the weight of a radionuclide with a specific radioactivity S R after t seconds is m, then T 0.1= 1 / λ × {ln(10) + ln(S R × m)} + t can be expressed as

[0034] Since the neutron capture cross section σn of most nuclides is inversely proportional to the neutron velocity, the capture cross section σn (0.353 meV) of cold neutrons (here, the boiling point of liquid helium, -268.9 °C) was calculated based on the value of σn (0.0253 eV) of thermal neutrons (20 °C) in JENDL-5 of the Nuclear Data Research Group of the Japan Atomic Energy Agency (citation source 2; described at the end). The value of σn (0.353 meV) is 8.47 times the value of σn (0.0253 eV). Note that nuclides with a capture cross section not inversely proportional to the neutron velocity are set to be equal to or greater than the value of thermal neutrons.

[0035] The neutron capture probability σp of a nuclide is expressed as the ratio of the neutron capture cross section σn to the nuclear cross section σ. Assuming the mass number of the nuclide is Z, the atomic radius is R = 1.25 × Z 1 / 3 〔fm〕, and the nuclear cross section σ = πR 2 was calculated. [Japan Atomic Energy Agency: Representation of Atoms or Atomic Nuclei, Number Density, Nuclear Radius, Unit System (03-06-01-03)] If σp of the neutron-irradiated nuclide is 1 or more, one neutron is captured and the nuclide is converted, and its weight becomes 0 g. The weight of the nuclide with an increased mass number by 1 becomes the weight of the nuclide that captured the neutron. Furthermore, if σp of the captured nuclide is 1 or more, it is converted to a nuclide with an increased mass number by 2, and the weight of this nuclide becomes the sum of the weights of these nuclides. If σp is 1 or less, the weight of the irradiated nuclide becomes (1 - σp) times, assuming that the weight of the nuclide converted to the converted nuclide is σp times.

[0036] A certain radioactive nuclide A (decay constant λ A ) decays, and the daughter nuclides B (same λ B ), C (same λ C ), D (same λ D ) generated successively are radioactive nuclides, and assuming that the daughter nuclide E is a stable nuclide, the weights of the radioactive nuclides at any time t are N A , N B , N C , N D , N EThen, the following system of simultaneous differential equations holds for these weights.

[0037]

Equation

[0038] If the initial weight of radionuclide A at t = 0 is N 0 then, by multiplying both sides of Equation (1) by exp(-λ A ×t) and integrating with respect to t, Equation (6) is obtained. The initial weights of radionuclides B, C, D, and stable nuclide E are 0. Substituting Equation (6) into Equation (2) and solving the differential equation gives Equation (7). Similarly, solving Equations (3) - (5) gives Equations (8) - (10). The nuclide weights N A (t), N B (t), N C (t), N D (t), N E (t) at any time t are obtained from the equations (6) - (10) shown in [Equation 2].

[0039]

Equation

[0040] After recovering actinides such as uranium and plutonium by methods such as the PUREX process including the cooling period from the gas generated from nuclear fuel removal, after a certain period of time, the soluble nuclides and the insoluble nuclides are separated into a soluble material tank and an insoluble material tank, and the change in nuclide weight is calculated. The calculation used the calculation function of the spreadsheet software Excel worksheet of Microsoft. Hereafter, unless otherwise stated, neutron irradiation refers to cold neutron irradiation, and neutron capture refers to cold neutron capture.

[0041] Table 1A shows a calculation example of obtaining the change in nuclide weight when irradiating nuclides with neutrons. In the vertical direction, starting from column A, row 3, nuclides are listed in ascending order of atomic number for each same mass number. The mass number z is in ascending order as z1, z2, z3, ···, and the atomic symbol and mass number are represented as Az, Bz, Cz, ···. Note that the atomic number is not shown in this table. Also, nuclides with m attached to the mass number represent nuclear isomers. Horizontally, column A shows the nuclide, column B shows the decay type, column C shows the half-life τ, column D shows the decay constant λ, and column E shows the neutron capture probability σp (the ratio of the neutron capture cross section σn to the nuclear cross section σ). However, half-lives are not listed. The value of σp for solid nuclides in the soluble and refractory nuclides with neutron energy is 0.353 meV, and for gaseous nuclides in the gaseous nuclides, it is 0.0253 eV. However, in this table, the actual values ​​are shown as shown. Column F shows the time required for fuel removal t 0 The weight of the nuclide after the time (days) is recorded, and the status of nuclide transmutation due to the first neutron irradiation is shown in column G, with +1n recorded for nuclides with σp of 1 or more, and if the σp of a transmuted nuclide that has captured a neutron and increased its mass number by 1 is 1 or more, this nuclide is recorded as +1n, and the original nuclide that has a mass number less than 1 is recorded as +2n. Cells of nuclides with no σp recorded are marked with ⇒, and cells of nuclides not irradiated with neutrons (refractory nuclides and gaseous nuclides produced by decay in the soluble matter tank, soluble nuclides and gaseous nuclides produced by decay in the refractory matter tank, and gaseous nuclides excluding iodine irradiated with the second neutron and soluble nuclides produced by decay in the gas tank) are also marked with ⇒. Nuclides that have been transmuted by capturing neutrons are indicated with <>, and +1n, +2n, or ··· are recorded for the nuclide (element symbol and mass number) before transmutation within <>. Column H shows the cumulative weight after neutron irradiation, and the nuclides that were converted by capturing neutrons during neutron irradiation are left blank at 0g. 1 Enter the time. t for the first neutron irradiation 1 The weights after 2000 hours are displayed in columns I to K, and their totals are displayed in column L. The calculations are performed by increasing the mass number. The total weights of the nuclides in the columns F, H, L, and N are displayed in the bottom row of the cells, ΣNt0, ΣNt0 * , ΣNt1, ΣNt1 * As these total values ​​are equal, the law of conservation of mass holds true, and the correctness of the calculation formula can be confirmed. The total weight of nuclides in column L and the cumulative weight of columns H and N is 1×10 -40 (Hereinafter referred to as 1E-40) In principle, if it is less than 1g, it will be displayed as 0g. Column M shows the status of nuclide conversion by the second neutron irradiation, which is the same as column G. However, in the soluble material tank and the gas tank, iodine with σp > 1 is different from column G and becomes +1n or +2n, and the other iodine cells are denoted as ⇒. Column N shows the cumulative weight after the second neutron irradiation, and the nuclides converted by capturing neutrons during neutron irradiation are left blank. Although not described in Table 1A, enter the second storage time t in seconds in the first row of column O 2 time, and then, similar to columns I - K, display the nuclide weights after neutron irradiation for t 2 time in columns O - Q, and display the sum in column R. Further, calculate by increasing the mass number. The mass number and atomic number of the nuclides to be calculated are described in specific examples. Here, the case of obtaining the change in nuclide weights in the soluble material tank and the gas tank is described. When obtaining the change in nuclide weights in the insoluble material tank, replace t 1 with t 1 ’, and replace t 2 with t 2 ’. The following explains the method for obtaining the nuclide weights of these nuclides after time t when the parent nuclides (decay mode, decay constant) after neutron irradiation decay radioactively into daughter nuclides. In the table, t 1 is displayed as t1 in half - width characters. 1

[0042]

Table 1A

[0043] Taking the radioactive nuclide Az1m with mass number z1 as the parent nuclide (m represents the nuclear isomer), when it decays as Az1m(IT,λaz1m)→Az1(β,λaz1)→Bz1(β,λbz1)→Cz1m(IT,λcz1m)→Cz1(stable), the weights of the nuclides Az1m, Az1, Bz1, Cz1m, and Cz1 after the first neutron irradiation for t 1 time are rewritten from equations (6) - (10) shown in [Equation 2] as follows, with the initial weight N 0Rewrite \(t\) as \(t1\) in the cumulative weight \(Naz1m\) of nuclide \(Az1m\). Here, \(*\) represents multiplication, and \(\lambda cz1 = 0\). Also, the subscript (number) of \(N\) indicates the order of decay, showing that when the same nuclide appears in different decays, it represents different decay reactions. For example, \(Bz1\) appears in equations (13) and (17).

[0044]

Number

[0045] If the decay constant \(\lambda\) of each nuclide on the right side of equations (11) to (15) is rewritten as the cell name in the corresponding row of column D (\(\lambda\)), the initial weight \(Naz1m\) as the cell name "H3", \(t1\) as the cell name "I$1", and then these rewritten right sides including the equal sign are written into cells I3 to I7 in column I respectively, then the 1 calculation results of the weights of the corresponding nuclides after \(t\) hours will be displayed in these cells. An example of the content of the cells in the written worksheet is shown within " ". In cell I3, the right side of equation (11) "=H3*exp(-$D3*I$1)" is written, and in cell I4, the right side of equation (12) "=H3*$D3*{exp(-$D3*I$1)-exp(-$D4*I$1)} / ($D4-$D3)" is written in half-width characters. Here, \($\) indicates an absolute reference.

[0046] Similarly, when the radionuclide \(Az1\) decays to \(Az1(β,\lambda az1)→Bz1(β,\lambda bz1)→Cz1m(IT,\lambda cz1m)→Cz\) (stable), at 1 time \(t\), the weights of nuclides \(Az1\), \(Bz1\), \(Cz1m\) and \(Cz1\) are rewritten from equations (6) to (9) shown in [Number 2] as follows, with the initial weight \(N\) 0 rewritten as the cumulative weight \(Naz1\) of nuclide \(Az1\) and \(t\) rewritten as \(t1\).

[0047]

Number

[0048] If the decay constant λ of each nuclide on the right side of Formulas (16) to (19) is written to the cell name in the corresponding row of column D (λ), the initial weight Naz1 is written to the cell name "H4", t1 is written to the cell name "I$1", and these rewritten right sides including the equal sign are written to the cells in rows 4 to 7 of column J respectively, then t 1 The calculation results of the weights of the corresponding nuclides after t hours are displayed in these cells. An example of the content of the cells in the written worksheet is shown within " ". In cell J4, the right side of Formula (16) "=H4*exp(-$D4*I$1)" is written, and in cell J7, the right side of Formula (17) "=H4*$D4*{exp(-$D4*I$1)-exp(-$D5*I$1)} / ($D5-$D4)" is written in half-width characters. The radioactive nuclide Bz1 (σp>1) captures neutrons by neutron irradiation and is converted into the nuclide Bz2. The cumulative weight (cell H5) immediately after irradiation is 0 g, but t 1 After t hours, the nuclide Bz1 is generated by the decay of the nuclides Az1m and Az1. These weights are the right sides of N3bz1(t1) in Formula (13) and N2bz1(t1) in Formula (17). If the decay constant λ of each nuclide in the formula is written to the cell name in the corresponding row of column D (λ), the initial weights are written to the cell names "H3" and "H4" of the cumulative weights of the respective nuclides, t is written to the cell name "I$1" where t is written as t1, and the rewritten right sides including the equal sign are written to cell I5 and cell J5 respectively, then t 1 The calculation results of the weight of the nuclide Bz1 after t hours are displayed in these cells.

[0049] When the radioactive nuclide Cz1m decays to Cz1m(IT,λcz1m)→Cz1 (stable), t 1 The weights of the nuclides Cz1m and Cz1 after t hours are rewritten from Formulas (6) and (7) shown in [Equation 2] as follows, and the initial weight N 0 is rewritten as the cumulative weight Ncz1m of the nuclide Cz1m, and t is rewritten as t1.

[0050]

Equation

[0051] If the decay constant λ of each nuclide on the right side of equations (20) to (21) is written to the cell name in the corresponding row of column D (λ), the initial weight Ncz1m is written to the cell name "H6", t1 is written to the cell name "I$1", and the right sides of the two rewritten equations including the equal sign are written to the cells in rows 6 to 7 of column K, then 1 The calculation results of the weights of the corresponding nuclides after t hours are displayed in these cells. The stable nuclide Cz1 (σp > 1) captures neutrons by neutron irradiation and is converted to nuclide Cz2. The cumulative weight (cell H7) immediately after irradiation is 0 g, but 1 After t hours, due to the decay of nuclide Az1m, N5cz1(t1) in equation (15) is generated; due to the decay of nuclide Az1, N4cz1(t1) in equation (19) is generated; and due to the decay of nuclide Cz1m, N2cz1(t1) in equation (21) is generated. If the decay constant of each nuclide on the right side of these equations is written to the cell name in the corresponding row of column D (λ), the initial weight is written to the cell names of the cumulative weights of each nuclide "H3", "H4", "H6", and t is written to the cell name of t1 "I$1", and the rewritten right sides of these equations including the equal sign are written to cells I7, J7, and K7, then 1 The calculation result of the weight of nuclide Cz1m generated after t hours is displayed in the cell. In column L, for nuclides Az1m, Az1, Bz1, Cz1m, Cz1 at 1 The nuclide weights Naz1mt1, Naz1t1, Nbz1t1, Ncz1mt1, Ncz1t1 after t hours are obtained by summing the cells in the same row of columns I to K. Naz1mt1 = N1az1m(t1), Naz1t1 = N2az1m(t1) + N1az1(t1), Nbz1t1 = N3bz1(t1) + N2bz1(t1), Ncz1mt1 = N4cz1m(t1) + N3cz1m(t1) + N1cz1m(t1), Ncz1t1 = N5cz1(t1) + N4cz1(t1) + N2cz1(t1). An example of the content of the cells in the worksheet is shown in " ". In cell L4, "=I4 + J4 " is written in half-width characters.

[0052] The weight of the radionuclide Bz2 [σp = 0.8] with a mass number increased by 1 only increases by Nbz1 due to nuclide conversion by neutron capture of the nuclide Bz1 [σp > 1]. However, since 20% of the weight of the nuclide Bz1 is not nuclide-converted by neutron irradiation, the cumulative weight immediately after irradiation is Nbz2’ = 0.2×(Nbz1 + Nbz2). When the nuclide Bz2 decays to Bz2(β,λbz2) → Cz2(β,λcz2) → Dz2 (stable), at time t 1 The weights of the nuclides Bz2, Cz2, and Dz2 at time t are obtained by rewriting the equations (6) to (8) shown in [Equation 2] as follows, with the initial weight N 0 rewritten as the cumulative weight Nbz2’ of the nuclide Bz2 and t rewritten as t1. However, λdz2 = 0.

[0053]

Equation

[0054] By replacing the decay constant λ of each nuclide on the right side of equations (22) to (24) with the cell name in the corresponding row of column D (λ), the initial weight Nbz2’ with the cell name "H8", and t1 with the cell name "I$1", and writing the rewritten right sides including the equal sign into cells I8 to 10 in column I respectively, the 1 calculation results of the weights of the corresponding nuclides at time t will be displayed in these cells. An example of the content of the cells in the written worksheet is shown within " ". In cell I8, "=0.2*(F5 + F8)*exp(-$D8*I$1)" is written in half-width characters, and in cell I9, "=0.2*(F5 + F8)*F8*{(exp(-$D8*I$1)-exp(-$D9*I$1)} / ($D9 - $D8)" is written. The weight of the radionuclide Cz2 increases by Ncz1 due to nuclide conversion by neutron capture of the nuclide Cz1 (σp > 1) by neutron irradiation, and the cumulative weight after irradiation is Ncz2’ = Ncz1 + Ncz2. When the nuclide Cz2 decays to Cz2(β,λcz2) → Dz2 (stable), at time t 1 The weights of the nuclides Cz2 and Dz2 at time t are obtained by rewriting equations (1) and (2) shown in [Equation 2] as follows, with the initial weight N 0 rewritten as the cumulative weight Ncz2’ of the nuclide Cz2 and t rewritten as t1.

[0055]

Number

[0056] If the decay constant λ of each nuclide is rewritten to the cell name in the corresponding row of column D (λ), the initial weight Ncz2’ is rewritten to the cell name “H9”, t1 is rewritten to the cell name “I$1”, and both rewritten right sides including the equal sign are written into the cells in rows 9 to 10 of column J, then 1 The calculation results of the weights of the corresponding nuclides after t hours are displayed in the cells in rows 9 to 10 of column J. The stable nuclide Dz2 (σp > 1) is converted into the nuclide Dz3 by neutron irradiation and the cumulative weight (cell H10) is 0 g, but 1 The nuclide Dz2 is generated by the β decay of the nuclides Bz2 and Cz2 after t hours. If the decay constant λ of each nuclide is rewritten to the cell name in the corresponding row of column D (λ) on the right sides of N3dz1(t1) in Equation (24) and N2dz1(t1) in Equation (26), the initial weights of both equations are rewritten to the cell names “H8” and “H9” of the cumulative weights of the corresponding nuclides, t1 is rewritten to the cell name “I$1”, and both rewritten right sides including the equal sign are written into the cells I10 and J10 respectively, then 1 The calculation results of the weights of the nuclide Dz2 generated by the decay after t hours are displayed in the cell. For the weight of the nuclide Dz2 generated by the ec decay of the nuclide Ez2, the decay constant of each nuclide on the right side of Equation (28) is rewritten to each cell name in the corresponding row of column D (λ), the initial weight N 0 is rewritten to the cell name “H11” of the cumulative weight Nez2 of the nuclide Ez2, t1 is rewritten to the cell name “I$1”, and the rewritten right side including the equal sign is written into the cell K10, then 1 The calculation results of the weights of the corresponding nuclides after t hours are displayed in the cell. When the radioactive nuclide Ez2 decays by ec decay into a stable nuclide Dz2 with an atomic number 1 less, Ez2(ec,λez1) → Dz2(stable), then 1 The weights of the nuclides Ez2 and Dz2 after t hours are rewritten from the equations (6) and (7) shown in [Number 2] as follows, and the initial weight N 0 is rewritten to the cumulative weight Nez2 of the nuclide Ez2, and t is rewritten to t1.

[0057]

Number

[0058] Replace the decay constant λ of each nuclide on the right side of Equation (27) to Equation (28) with the cell name in the corresponding row of column D (λ), the initial weight Nez2 with the cell name "H11", t1 with the cell name "I$1", and write the rewritten right sides including the equal sign into cells in column K, rows 11 to 10 respectively, then the calculation result of the weight of the corresponding nuclide after t 1 The weight of the corresponding nuclide after the time will be displayed in the cell. In column L, for nuclides Bz2, Cz2, Dz2, Ez2 at t 1 The weights Nbz2t1, Ncz2t1, Ndz2t1, Nez2t1 after time t are obtained by summing the cells in the same row of columns I to K. Nbz2t1 = N1bz2(t1), Ncz2t1 = N2cz2(t1) + N1cz2(t1), Ndz2t1 = N3dz2(t1) + N2dz2(t1) + N2ez2(t1), Nez2t1 = N1ez2(t1) + N2gz6(t1). Moreover, N2gz6(t1) is generated by the α decay of nuclide Gz6 as described later.

[0059] The weight of radioactive nuclide Bz3 (σp not described) with a mass number increased by 2 is obtained by neutron capture of isotopes Bz1 (σp > 1) and Bz2 (σp = 0.8) during the first neutron irradiation, Nbz3’ = Nbz3 + 0.8×(Nbz1 + Nbz2). When nuclide Bz3 decays to Bz3(β, λbz3) → Cz3(β, λcz3) → Dz3(β, λdz3) → Ez3 (stable), at t 1 The weights of nuclides Bz3, Cz3, Dz3, and Ez3 after time t are obtained by rewriting Equations (6) to (9) shown in [Equation 2] as follows, with the initial weight N 0 replaced by the cumulative weight Nbz3’ of nuclide Bz3 and t replaced by t1. However, λez3 = 0.

[0060]

Equation

[0061] If you rewrite the decay constant λ of each nuclide on the right side of Eqs. (29) to (32) to the cell name in column D (λ) of the corresponding row, rewrite the initial weight Nbz3’ to the cell name “H12”, rewrite t1 to the cell name “I$1”, and write these rewritten right sides including the equal sign to cells in rows 12 to 15 of column I, then 1 the calculation results of the weights of the corresponding nuclides after t hours will be displayed in these cells. An example of the content of the cells in the written worksheet is shown within “ ”. For cell I12, “={F12 + 0.8*(F5 + F8)}*exp(-$D12*I$1)” is written in half-width characters. The radioactive nuclide Cz3 (σp > 1) is converted into nuclide Cz4m by neutron capture and the cumulative weight (cell H13) is 0, but 1 at t hours, Cz2 is generated by the β decay of nuclide Bz2. If you rewrite the decay constant λ of each nuclide on the right side of Eq. (30) N2cz3(t1) to the cell name in column D (λ) of the corresponding row, rewrite the initial weight Nbz3’ to the cell name “H12”, rewrite t1 to the cell name “I$1”, and write the rewritten equation including the equal sign to cell I13, then 1 the calculation result of the weight of nuclide Cz2 after t hours will be displayed in that cell.

[0062] The weight of the radioactive nuclide Dz3 only increases by Ndz2 due to the neutron capture of the isotope nuclide Dz2 (σp > 1), and the cumulative weight becomes Ndz3’ = Ndz2 + Ndz3. When nuclide Dz3 decays to Dz3(β, λdz3) → Ez3 (stable), 1 the weights of nuclides Dz3 and Ez3 after t hours rewrite Eqs. (1) and (2) shown in [Equation 2] as follows, and the initial weight N 0 is rewritten to the cumulative weight Ndz3’ of nuclide Dz3, and t is rewritten to t1.

[0063]

Equation

[0064] If you rewrite the decay constant λ of each nuclide on the right side of Eqs. (33) to (34) to the cell name in column D (λ) of the corresponding row, rewrite the initial weight Ndz3’ to the cell name “H14”, rewrite t1 to the cell name “I$1”, and write these rewritten right sides including the equal sign to cells in rows 14 to 15 of column J, then 1The calculation result of the weight of the corresponding nuclide after time is displayed in the cell. The stable nuclide Ez3 (σp>1) is converted into nuclide Ez4 by neutron capture, and the cumulative weight (H15 cell) becomes 0 g, but t 1 After time, nuclide Ez3 is generated by the decay of nuclides Bz3 and Dz3. In the right side of formula (32) N4ez3 and the right side of formula (34) N2ez3, the decay constant λ of each nuclide is written to the cell name in the corresponding row of column D (λ), the initial weight is written to the cell names "H12" and "H14" indicating the respective cumulative weights, t1 is written to the cell name "I$1", and if the rewritten two formulas including the equal sign are written to cells I15 and J15 respectively, then t 1 The calculation result of the weight of nuclide Ez2 after time is displayed in the cell. In column L, for nuclides Bz3, Cz3, Dz3, Ez3 at t 1 The weights of nuclides Nbz3t1, Ncz3t1, Ndz3t1, Nez3t1 after time are obtained by the sum of the cells in the same row of columns I to K. Nbz3t1 = N1bz3(t1), Ncz3t1 = N2cz3(t1), Ndz3t1 = N3dz3(t1) + N1dz3(t1), Nez3t1 = N4ez3(t1) + N2ez3(t1).

[0065] The weight of the radioactive nuclide Cz4m with a mass number increased by 3 only increases by Ncz3 due to neutron capture of nuclide Cz3 (σp>1), and the cumulative weight becomes Ncz4m’ = Ncz3 + Ncz4m. When nuclide Cz4m decays to Cz4m(IT, λcz4m) → Cz4(β, λcz4) → Dz4(stable), t 1 The weights of nuclides Cz4m, Cz4, Dz4 after time are rewritten from formulas (6) to (8) shown in [Equation 2] as follows, and the initial weight N 0 is rewritten to the cumulative weight Ncz4m’ of nuclide Cz4m, and t is rewritten to t1. However, λdz4 = 0.

[0066]

Equation

[0067] Replace the decay constant λ of each nuclide on the right side of Equations (35) to (37) with the cell name in the corresponding row of column D (λ), the initial weight Ncz4m’ with the cell name “H16”, and t with the cell name “I$1” of t1. Then, write the rewritten right sides including the equal sign into cells I16 to I18 in column I. Then, for t 1 The calculation result of the weight of the corresponding nuclide after t hours is displayed in the cell. An example of the content of the cell in the written worksheet is shown within “ ”. For cell I16, “=(F13 + F16)*exp(-$D16*I$1)” is written in half-width characters. The radioactive nuclide Cz4 (σp>1) captures neutrons and is nuclide-converted to Cz5, and the H17 cell (cumulative weight) becomes 0. However, for t 1 After t hours, Cz4 is produced by the IT decay of the radioactive nuclide Cz4m. Replace the decay constant λ of each nuclide on the right side of Equation (36) N2cz4(t1) of the nuclide Cz4m with the cell name in the corresponding row of column D (λ), the initial weight Ncz4m’ with the cell name “H16”, and t1 with the cell name “I$1”. Then, write the rewritten equation including the equal sign into cell I17. Then, for t 1 The calculation result of the weight of the corresponding nuclide after t hours is displayed in the cell.

[0068] The radioactive nuclide Ez4 with a nuclear energy level higher than that of the stable nuclide Dz4 decays to the stable nuclide Dz4 with an atomic number 1 less by ε(β+) decay. The weight of the nuclide Ez4 increases by only Nez3 due to neutron capture of the isotope Ez3 (σp>1), and the cumulative weight becomes Nez4’ = Nez3 + Nez4. When the nuclide Ez4 decays to Ez4(ε,λez4) → Dz4 (stable), for t 1 The weights of the nuclides Dz3 and Ez3 after t hours are rewritten from Equations (1) and (2) shown in [Equation 2] as follows. For the initial weight N 0 Replace it with the cumulative weight Nez4’ of the nuclide Ez4 and t with t1.

[0069]

Equation

[0070] If the decay constant λ of each nuclide is rewritten as the cell name in the corresponding row of column D (λ), the initial weight Nez4’ as the cell name "H19", and t1 as the cell name "I$1" on the right sides of equations (38) and (39), and the rewritten equations including the equal sign are written into the cells in column J, rows 19 to 18, then 1 The calculation result of the weight of the corresponding nuclide after t hours will be displayed in the cell. In column L, for the nuclides Cz4m, Cz4, Dz4, Ez4 at 1 The nuclide weights Ncz4mt1, Ncz4t1, Ndz4t1, Nez4t1 after t hours are obtained by the sum of the cells in the same row of columns I to K. Ncz4mt1 = N1cz4m(t1), Ncz4t1 = N2cz4(t1), Ndz4t1 = N3dz4(t1) + N2dz4(t1), Nez4t1 = N1ez4(t1).

[0071] The weight of the radioactive nuclide Cz5 with a mass number increased by 4 increases only by Ncz4 due to neutron capture of isotope Cz4 (σp > 1), and the cumulative weight is Ncz5’ = Ncz4 + Ncz5. When nuclide Dz5 undergoes β decay, if the nuclear energy level of nuclide Ez5m is higher than that of nuclide Dz5, Dz5 does not decay into Ez5m but decays into Ez5. When Cz5(β, λcz5) → Dz5(β, λdz5) → Ez5 (stable) decays, at 1 The weights of nuclides Cz5, Dz5, Ez5 after t hours are rewritten from equations (6) to (8) shown in [Equation 2] as follows, and the initial weight N 0 is rewritten as the cumulative weight Ncz5’ of nuclide Cz5, and t is rewritten as t1. However, λez5 = 0.

[0072]

Equation

[0073] If the decay constant λ of each nuclide is rewritten as the cell name in the corresponding row of column D (λ), the initial weight Ncz5’ as the cell name "H20", and t1 as the cell name "I$1" on the right sides of equations (40) to (42), and these rewritten right sides including the equal sign are written into the cells in column I, rows 20 to 21 and row 23, then 1The calculation result of the weight of the corresponding nuclide after time is displayed in the cell. An example of the content of the cell in the written worksheet is shown within " ". For cell I20, "=(F17+F20)*exp(-$D20*I$1)" is written in half-width characters. The radioactive nuclide Dz5 (σp>1) captures neutrons and is nuclide-converted to Dz6, and the cumulative weight (cell H21) becomes 0, but t 1 After time, nuclide Dz5 is produced by the β decay of radioactive nuclide Cz5. In the right side of formula (41) N2dz5, rewrite the decay constant λ of each nuclide to the cell name in the corresponding row of column D (λ), rewrite the initial weight Ncz5’ to the cell name "H20", and t1 to the cell name "I$1", and write this right side including the equal sign into cell I21, then t 1 The calculation result of the weight of nuclide Dz5 after time is displayed in the cell. When radioactive nuclide Ez5m decays to Ez5m(IT, λez5m) → Ez5 (stable), t 1 The weights of nuclide Ez5m and Ez5 after time are rewritten from formulas (6) and (7) shown in [Equation 2] as follows, and the initial weight N 0 Rewrite to the cumulative weight Nez5m of nuclide Ez5m and rewrite t to t1.

[0074]

Equation

[0075] In the right sides of formulas (43) and (44), rewrite the decay constant λ of each nuclide to the cell name in the corresponding row of column D (λ), rewrite the cumulative weight Nez5m to the cell name "H22", and t1 to the cell name "I$1", and write both right sides including the equal sign into cells J22 - 23 of column J respectively, then t 1 The calculation result of the weight of the corresponding nuclide after time is displayed in cells J22 - 23 of column J. The stable nuclide Ez5 (σp>1) is nuclide-converted to the isotope Ez6 and the cumulative weight (cell H23) becomes 0 g, but t 1After a certain time, nuclides Cz5 and Ez5m decay as parent nuclides to produce Ez5 by decay. In the right side of Equation (42) N3ez5(t1) and the right side of Equation (44) N2ez5(t1), rewrite the decay constant λ of each nuclide to the cell name in the corresponding row of column D (λ), rewrite the cumulative weight of each to cell names "H20" and "H22", rewrite t1 to cell name "I$1", and write both right sides including the equal sign to cell I23 and cell J23 respectively, then t 1 The calculation result of the weight of nuclide Ez5 after a certain time is displayed in this cell. In column L, for nuclides Cz5, Dz5, Ez5m, and Ez5 at t 1 The nuclide weights Ncz5t1, Ndz5t1, Nez5mt1, and Nez5t1 after a certain time are obtained by summing the cells in the same row of columns I - K. Ncz5t1 = N1cz5(t1), Ndz5t1 = N2dz5(t1), Nez5mt1 = N1ez5m(t1), Nez5t1 = N3ez5(t1)+N2ez5(t1).

[0076] The weight of radioactive nuclide Dz6 with a mass number increased by 5 increases by only Ndz5 due to neutron capture of isotope Dz5 (σp > 1), and the cumulative weight immediately after neutron irradiation is Ndz6’ = Ndz5 + Ndz6. When nuclide Dz6 decays to Dz6(β,λdz6)→Ez6(β,λez6)→Fz6 (stable), at t 1 The weights of nuclides Dz6, Ez6, and Fz6 after a certain time are rewritten from Equations (6) - (8) shown in [Equation 2] as follows, with the initial weight N 0 rewritten to the cumulative weight Ndz6’ of nuclide Dz6, and t rewritten to t1. However, λfz6 = 0

[0077]

Equation

[0078] In the right sides of Equations (45) - (47), rewrite the decay constant λ of each nuclide to the cell name in the corresponding row of column D (λ), rewrite the cumulative weight Ndz6’ to cell name "H24", rewrite t1 to cell name "I$1", and write these right sides including the equal sign to cells in rows 24 - 26 of column I respectively, then t 1The calculation result of the weight of the corresponding nuclide after time is displayed in cells I24 to I26 of column I. Taking an example of the content of a cell in the written worksheet, the cell I24 is written with "=(F21+F24)*exp(-$D24*I$1)" in half-width characters. The weight of the radionuclide Ez6 increases only by Nez5 due to neutron capture of the isotope Ez5 (σp>1), and the cumulative weight becomes Nez6’ = Nez5 + Nez6. When the nuclide Ez6 decays to Ez6(β,λez6) → Fz6 (stable), at time t 1 The weights of the nuclides Ez6 and Fz6 after time are rewritten from the formulas (6) and (7) shown in [Equation 2] as follows, with the initial weight N 0 replaced with the cumulative weight Ndz6’ of the nuclide Dz6, and t replaced with t1. However, λfz6 = 0.

[0079]

Equation

[0080] By replacing the decay constant λ of each nuclide on the right side of formulas (48) and (49) with the cell name in the corresponding row of column D (λ), the cumulative weight Ndz6’ with the cell name "H24", and t1 with the cell name "I$1", and writing the right sides including the equal sign into cells J25 to J26 of column J respectively, then for t 1 the calculation result of the weight of the corresponding nuclide after time is displayed in the cell. For the stable nuclide Fz6 at time t 1 the weight after time is the initial value Nfz6 plus the weight generated by the β decay of the radionuclides Dz6 and Ez6. By replacing the decay constant λ of each nuclide on the right side of formula (47) N3fz6(t1) and formula (49) N2fz6(t1) with the cell name in the corresponding row of column D (λ), and writing the right sides including the equal sign into cells I26 and J26 respectively, then for t 1 the calculation result of the weight of the nuclide Fz6 after time is displayed in the cell. Since the radionuclide Gz6 decays by α decay, with the atomic number decreasing by 2 and the mass number decreasing by 4 to decay into the nuclide Ez1, when the nuclide Gz6 decays to Gz6(α) → Ez2 (stable), at time t 1 the weights of the nuclides Gz6 and Ez2 after time are rewritten from the formulas (6) and (7) shown in [Equation 2] as follows, with the initial weight N 0Rewrite t as t1 in the cumulative weight Ngz6 of nuclide Gz6.

[0081]

Number

[0082] If, in the right - hand sides of Equation (50) and Equation (51), replace the decay constant λ of each nuclide with the cell name in the corresponding row of column D (λ), the cumulative weight Ngz6 with the cell name "H27", and the cell name of t1 with "I$1", and then write both right - hand sides including the equal sign into the cells of column J, row 27 and row 11 respectively, then 1 the calculation result of the weight of the corresponding nuclide after t hours will be displayed in that cell. In column L, the weights Ndz6t1, Nez6t1, Nfz6t1, Ngz6t1 of nuclides Dz6, Ez6, Fz6, Gz6 after t 1 hours are obtained as the sum of the cells in the same row of columns I - K. Ndz6t1 = N1dz6(t1), Nez6t1 = N2ez6(t1)+N1ez6(t1), Nfz6t1 = Nfz6+N3fz6(t1)+N2fz6(t1), Ngz6t1 = N1gz6(t1).

[0083] For the second neutron irradiation, after t 2 hours of storage, although not shown in Table 1A, enter t2 expressed in seconds into the cell of column O, row 1, and use the cumulative weight of the first neutron irradiation and t 1Copy the formulas in columns H to L (cells H3 to L27) that display the weight of the nuclide after a certain time and the total weight, and paste them as they are into columns N to R (cells N3 to R27). In the formula, replace t1 with t2 (replace I1 with O1 in the formula), set the cells in column D for the decay constant λ in the formula as fixed addresses (absolute references), and set the cells related to weight as relative reference addresses. In formulas (11) to (51), only t1 is changed to t2, and the cumulative weight in column H corresponding to the initial weight is changed to the cumulative weight in column N. The formulas in the pasted cells after movement are automatically changed. For example, the formula in cell I3, "=H3*exp(-$D3*I$1)", is written in half-width characters as "=N3*exp(-$D3*O$1)". Note that $ means absolute reference. t 2 The calculation results of the weight of the nuclide after a certain time are displayed in the corresponding cells in columns O to Q. In column R, for all nuclides described in column A, the t 2 The weight of the nuclide after a certain time is obtained by the sum of the cells in the same row in columns O to Q.

[0084] In Table 1B, for the Ni-th neutron irradiation and a certain period t after irradiation s This shows a calculation example for obtaining the weight change of the nuclide after leaving it for a certain time. This table shows an example of the Ni-th neutron irradiation, and the column names (AA to AN) are provisional names and are different in the actual table. Enter t in cell AF1 in seconds, and considering the value of σp in column E for the total weight of the nuclides immediately before the Ni-th neutron irradiation displayed in column AC, copy it to each cell in column AE under the neutron irradiation conditions displayed in column AD. ⇒ indicates that the weight of the cell in column AC in the same row is copied as it is to the cell in column AE. The cumulative weight in column AE for nuclides with σp of 1 or more is 0 g, and for those with σp of less than 1, it is the cumulative weight considering this neutron capture probability. Also, for cells displayed with <> for nuclides with non-described σp, the weight increased by nuclide conversion due to neutron capture of the same element with a smaller mass number is added (for example, cells AE9, AE14, etc.). For the t i time after the Ni-th neutron irradiation. i To obtain the weight of the nuclide after a certain time, copy the rewritten formulas (11) to (51) written in each cell in columns I to K for the first neutron irradiation in Table 1A as they are to each cell in columns AF to AH, and change the initial weight N 0 in the variables in the formula to the corresponding cell name of the cumulative weight in column AE, and replace t with the cell name "AF$1", then ti The calculation results of the nuclide weights after the time are displayed in the corresponding cells of columns AF to AH. For example, the difference between the formulas (11) to (15) displayed in cells of rows 3 to 7 in column I and the formulas (11) to (15) displayed in cells of rows 3 to 7 in column AF is that the variable t changes from t1 to ti, and the initial weight N 0 is only changed from Naz1m to Naz1mti-1. In column AI, the nuclide weights of all nuclides at t i After the time, the nuclide weights are obtained by summing the cells in the same row of columns AF to AH. However, for stable nuclides where σp is not described, the cumulative weight in column AE is added. For example, for the stable nuclides Dz4 and Fz6 in rows 18 and 26, for the former, AE18 is added to the sum of AF18 and AG18, and for the latter, AE26 is added to the sum of AF26 and AG26. This table describes the case of obtaining the nuclide weight changes in the soluble material tank and the gas tank. When obtaining the nuclide weight changes in the insoluble material tank, t i is replaced with t i ’, t s is replaced with t s ’, and Ni is replaced with Nj.

[0085]

Table 1B

[0086] At the t i After the time of the Ni-th neutron irradiation, in order to reduce the temperature and radioactivity of the stored material due to the decay energy of the radionuclide, t s is left for a period of time. t s To obtain the nuclide weight after leaving for t s time, enter the t 0 time expressed in seconds in cell AJ1, move the copied cells of the formulas (11) to (51) after rewriting written in each cell of columns I to K in the first neutron irradiation in Table 1A to each cell of columns AJ to AL, and change the initial weight N sThe calculation results of the nuclide weights after time are displayed in the corresponding cells of columns AJ to AL. The difference between the expressions (11) to (15) displayed in cells of rows 3 to 7 in column I and the expressions (11) to (15) displayed in cells of rows 3 to 7 in column AJ is only that the column name and the variable t1 are changed to ts, and the cumulative weight Naz1m is changed to Naz1mti. In column AN, for the nuclide t s The weight after time is obtained by the sum of the cells in the same row of columns AJ to AL. However, for stable nuclides, the cumulative weights in column AE are also added, corresponding to Cz1, Dz2, Ez3, Dz4, Ez5, and Fz6. Also, since no neutrons are irradiated, for nuclides with a cumulative weight of 0 g in column AE, since the decay series to daughter nuclides with this nuclide as the parent nuclide is not described, the sequential equations for this series are required. When the nuclide Bz1 in the 5th row decays as Bz1(β,λbz1)→Cz1m(IT,λcz1m)→Cz(stable), the weights of these nuclides after ts time are obtained by providing column AM and rewriting the expressions (6) to (8) shown in [Equation 2] in cells of rows 5 to 7 in column AM as follows, with the initial weight N 0 changed to the subtotal weight Nbz1ti of nuclide Bz1, and t changed to ts. However, λcz1 = 0.

[0087]

Equation

[0088] By replacing the decay constant λ of each nuclide on the right side of expressions (52) to (54) with the cell name of column D (λ) in the corresponding row, the cell name of the subtotal weight Nbz1ti "AI5", and ts with the cell name "AJ$1", and then writing these right sides including the equal sign into cells of rows 5 to 7 in column AM respectively, the s calculation results of the weights of the corresponding nuclides after time are displayed in cells of rows 5 to 7 in column AM. When the radionuclide Cz3 in the 13th row decays as Cz3(β,λcz3)→Dz3(β,λdz3)→Ez3(stable), for the s weights of these nuclides after time, rewrite the expressions (6) to (8) shown in [Equation 2] in cells of rows 13 to 15 in column AM as follows, with the initial weight N 0 changed to the subtotal weight Ncz3ti of nuclide Cz3, and t changed to ts. However, λez3 = 0

[0089]

Number

[0090] If the decay constant λ of each nuclide in the right sides of formulas (55) to (57) is written in the cell name of column D (λ) of the corresponding row, the cell name of the weight subtotal Ncz3ti, "AI13" cell, ts is rewritten in the cell name "AJ$1", and these formulas including the equal sign are written in the cells of rows 13 to 15 in column AM respectively, then t s The calculation results of the weights of the corresponding nuclides after time t are displayed in the cells of rows 13 to 15 in column AM. Similarly, when the radionuclide Cz4 at the 17th row decays to Ez4 (stable) by (β, λdz4), to s obtain the weights of these nuclides after time t, rewrite the formulas (6) and (7) shown in [Number 2] in the cells of rows 17 to 18 in column AM as follows, and set the initial weight N 0 to the weight subtotal Ncz4ti of nuclide Cz4, and rewrite t to ts. However, λdz4 = 0.

[0091]

Number

[0092] If the decay constant λ of each nuclide in the right sides of formulas (58) and (59) is written in the cell name of column D (λ) of the corresponding row, the cell name of the weight subtotal Ncz4ti, "AI17" cell, ts is rewritten in the cell name "AJ$1", and both formulas including the equal sign are written in the cells of rows 17 and 18 in column AM respectively, then t s The calculation results of the weights of the corresponding nuclides after time t are displayed in the cells of rows 17 and 18 in column AM. Similarly, for the radionuclide Dz5 at the 21st row (β, λdz5) → Ez5 (stable), for s obtaining the weights of these nuclides after time t, rewrite the formulas (6) and (7) shown in [Number 2] in the cells of rows 21 and 23 in column AM as follows, and set the initial weight N 0 to the weight subtotal Ndz5ti of nuclide Dz5, and rewrite t to ts. However, λez5 = 0

[0093]

Number

[0094] If the decay constant λ of each nuclide is rewritten in the right-hand sides of Equation (60) and Equation (61) to the cell name in column D (λ) of the corresponding row, the cell name of the weight subtotal Ndz5ti to "AI21", and t to the cell name of ts "AJ$1", and both equations including the equal sign are written into cells AM21 and 23 respectively, then t s The calculation results of the weights of the corresponding nuclides after time will be displayed in cells AM column 21 and row 23. In the cells at the bottom row of columns AC, AE, AI, and AN in Table 1B, the total of the nuclide weights in these columns are denoted as ΣNti-1, ΣNti * , ΣNti, ΣNts, while in Table 1A, ΣNt0, ΣNt0 * , ΣNt1, ΣNt1 * Including these, if it is confirmed that all these numerical values are equal, it is based on the law of conservation of mass and reflects the correctness of the calculation formula.

Example

[0095] As an example according to the present invention, data on the weight transition of 879 kinds of FPs generated from the spent nuclear fuel of Reactor Unit 2 of the Tokyo Electric Power Fukushima Daiichi Nuclear Power Plant was used. [Data citation source 3; described at the end] In addition, 14 nuclides not described in the above data and 18 nuclides newly generated by neutron irradiation were added as calculation targets. A certain period t 0 The time is from several tens of days to several decades, and in this example, it is set to 180 days. In the soluble substance tank, the insoluble substance tank, and the gas tank, for nuclides with a weight of 1E-40 g or more 180 days after the removal of the spent nuclear fuel, for each same mass number, the nuclide, decay mode, half-life τ, decay constant λ, neutron capture probability σp, weight after 180 days are written into the corresponding cells, and the corresponding storage period is written into the corresponding cells. Columns are increased to display the nuclide weights corresponding to the number of neutron irradiations, and an Excel worksheet was created based on Tables 1A and 1B for the change over time of the nuclide weights when the present invention is applied. Since the worksheet would be more than 120 sheets when printed on A4 paper, it is omitted, and the calculation results for the nuclides in each tank are presented. The unit of the half-life is expressed in seconds: s, minutes: m, hours: h, days: d, years: y. The neutron capture probability σp is expressed as the ratio of the neutron capture cross-section σn to the nuclear cross-section σ. The neutron capture cross-section σn(0.353 meV) was calculated based on σn(0.0253 eV) of JENDL-5 of the Nuclear Data Research Group of the Japan Atomic Energy Agency. Note that for nuclides where σn is not inversely proportional to the neutron velocity, the value is taken as that of thermal neutrons or higher. If the σp of a nuclide is 1 or more, it captures neutrons and undergoes nuclide conversion, and its weight becomes 0 g. The nuclide with an increased mass number has the weight of the nuclide that captured neutrons. Furthermore, if the σp of the captured nuclide is 1 or more, it is converted to a nuclide with a mass number increased by 2. If the σp of the converted nuclide is 1 or more, it further captures neutrons and undergoes nuclide conversion, and the mass number increases by 3. For example, the σp of 0.353 meV of barium isotopes are 53.7 for Ba132, 18.1 for Ba133m, 18.1 for Ba133, 9.89 for Ba134, and 38 for Ba135, and each captures 4 to 1 neutrons and is converted to 56Ba136m by nuclide conversion. In the present invention, the generated high-level radioactive waste is separated and stored into a soluble substance soluble in nitric acid and an insoluble substance that is hardly soluble or insoluble. For the former, neutrons are not irradiated to the stable insoluble substance generated by decay, and for the latter, neutrons are not irradiated to the stable soluble substance generated by decay. Therefore, the recovery amount of stable nuclides increases significantly compared to the case without tank separation. Also, in order to minimize the weight of the glass solidified body of high-level radioactive waste, as a result of calculating with the number of neutron irradiations being 3 to 16 times and the subsequent storage period being 3 days to 1 year as parameters, the irradiation interval was set to 30 days. The number of irradiation times varies for each tank.

[0096] (Nuclides in the soluble substance tank) When applying Table 1A and Table 1B to the nuclides in the soluble substance tank, the weights (F column) of the hardly soluble nuclides and gaseous nuclides after t0 days are 0 g, and since neutrons are not irradiated to the hardly soluble nuclides and gaseous nuclides generated by the decay of soluble nuclides after neutron irradiation, for these nuclides in the corresponding rows of G, M, ··· AD, ···For the cells in the column, display ⇒, and the cumulative weight after neutron irradiation is the total weight before irradiation. However, exclude iodine with σp ≥ 1 only for the second neutron irradiation. In the case of a decay series that does not contain soluble nuclides with the same mass number, since the initial weight is 0 g, nuclides of this mass number are excluded from the table (for example, 32Ge73m~32Ge75, 40Zr93~46Pd107, and 50Sn118~51Sb122). The calculation targets are from 2He4 to 72Hf178. For the first nuclide, the soluble nuclide 3Li6 undergoes neutron capture to decay into 3Li8(β, 0.84 s) → 4Be8(α, 8.2×10 -17 s) → 2He4 (stable), generating gaseous 2He4. For the last nuclide, the soluble stable nuclide 70Yb172 described in the JAEA data, and for non-described isotopes 70Yb173~176 with σp ≥ 1, the radioactive nuclide 70Yb177(β, 1.91 h) generated by nuclide conversion in the first neutron irradiation undergoes β decay to produce the soluble nuclide 71Lu177(β / IT, 160.4 d) with σp ≥ 1. This nuclide undergoes nuclide conversion in the second irradiation to produce the β decay of 71Lu178m(β, 23.1 m), resulting in the formation of the poorly soluble nuclide 72Hf178m(IT, 23.1 m) → 72Hf178 (stable). Nuclides with a mass number of 172 or more are newly generated nuclides by neutron irradiation. The weights of the gaseous nuclides and poorly soluble nuclides generated in the soluble material tank are described in the table of the soluble material tank.

[0097] Neutrons are irradiated Ni times only to the soluble nuclides in the soluble material tank, and after t i time storage, the generated gaseous nuclides are recovered into the gas tank, and the generated poorly soluble nuclides are recovered into the poorly soluble material tank A using a solid-liquid separation device or the like Ni times. Neutrons are not irradiated to substances other than soluble nuclides. In this example Assuming the number of irradiation times Ni is 9 , the storage period t i is, t 1 ~t 8 is 30 days, t 9 is 310 days (equivalent to 2 years from the removal of nuclear fuel), and t s is 4 years. In the soluble material tank, even if the soluble nuclides contained in the nitric acid solution after reprocessing by the PUREX method or the like are used for each solution, once denitrated and about 300 L of a new nitric acid solution with a concentration of 4 mol / L is added, the nuclides soluble in nitric acid may be in the form of nitrates or oxides. The nitric acid solution containing the nuclides soluble in this nitric acid is recovered in the soluble material tank. Although the solution temperature rises due to heat generation by radioactive decay, if heating is necessary to convert iodine from the liquid phase to the gas phase, the nitric acid solution evaporates. Therefore, it is necessary to maintain the nitric acid solution with a concentration of 4 mol / L at about 300 L after neutron irradiation. Based on Table 1A and Table 1B, when neutrons were irradiated on only the soluble nuclides in the soluble material tank under the aforementioned conditions, the change in the weight of the nuclides changed by decay was calculated using an Excel worksheet. The soluble nuclides in the soluble material tank are 237 species (160 radioactive nuclides and 77 stable nuclides), and the weight 180 days after nuclear fuel removal is 1097.3 kg for the soluble nuclides (397.0 kg for radioactive nuclides and 700.3 kg for stable nuclides). All these weights are the weights of individual nuclides.

[0098] Regarding the radioactive nuclides in the soluble material tank, Table 2A-1 shows the calculation results of the weight [unit: g] and radioactivity [unit: Bq] after 6 years for the weight 180 days after spent nuclear fuel removal, the case of leaving it unmanaged for 6 years, and the case of applying the present invention (irradiating only the soluble nuclides with neutrons under the aforementioned conditions). The radioactive solid nuclides 160 species with a weight of 371.5 kg are reduced to 15 species with a weight of 24.1 kg (14 species of soluble nuclides with 24.1 kg, and 1 species of insoluble nuclides with 3.4×10 -37 g, and no gaseous nuclides) by the countermeasures. All these weights are the weights of individual nuclides and not the weights of compounds such as oxides and nitrates. By the countermeasures, the radioactivity of the soluble nuclides is 268.9 PBq (P is peta), and the radioactivity of the insoluble nuclides has increased, but It is 1 zBq (z is zepto) or less . Among the 150 non-described radioactive soluble nuclides, 105 nuclides have a half-life of 10 days or less, which is short, and they will be approximately 0 g after 6 years of countermeasures. The soluble nuclides with a long half-life of 50 days or more 35The σp of the nuclide is 1 or more, and it is converted into a nuclide by neutron irradiation and the weight becomes 7.67E-50 g. This is due to the weight remaining without being captured in the ninth neutron irradiation 67Dy166m(β,1200y) generated by the β decay of 7.69E-50 g of 66Dy166 becomes 7.67E-50 g after 6 years remaining. The weight of 397.0 kg of soluble radionuclides present 180 days after the removal of nuclear fuel is reduced to 24.1 kg after 6 years by the countermeasures.

[0099]

Table 2A-1

[0100] For nuclides with a weight of 1E-40 g or more after the countermeasures among the radionuclides in the soluble material tank, Table 2A-2 shows the calculation results of the changes in weight and radioactivity when left untreated for 6 years and when the present invention is applied. The table shows the decay mode and half-life of the radionuclides generated in the soluble material tank, the neutron capture probability σp (0.353 meV), the nuclide weight [unit: g], and the radioactivity [unit: Bq]. Note that the weight is the weight of the nuclide alone, not the weight of compounds such as oxides and nitrates.

[0101]

Table 2A-2

[0102] Among the radioactive soluble nuclides generated in the soluble material tank, the radioactivity becomes 0.1 Bq or less for six nuclides: 48Cd116, 55Cs134 / 135, 58Ce141 / 142, 60Nd144. The nuclides whose radioactivity has decreased due to the countermeasures are 38Sr90, 39Y90, 48Cd116, 55Cs134 / 135, 58Ce141 / 142, 60Nd144, 62Sm151, 11 species of 63Eu154 / 155 and the nuclides whose radioactivity has increased are 3 species of 39Y91, 71Lu177m / 177 is. For the countermeasures where the radioactivity (weight) has decreased Among the 11 nuclides , for 38Sr90 and 48Cd116, σp is 0.09 and 0.54 respectively, there is no parent nuclide, and the half-lives of both are long. Part of them remains without being converted into a nuclide by neutron irradiation, but the weight decreases with the number of irradiations and decreases compared to after 6 years of being left untreated. The remaining9 nuclides 39Y90, 55Cs134 / 135, 58Ce141 / 142, 60Nd144, 62Sm151, 63Eu154 / 155 Although the σp is greater than 1 and the nuclide is converted by neutron irradiation 8 times and the weight becomes 0 g, these nuclides are converted by neutron irradiation for the 9th time to produce radioactive parent nuclides 38Sr90(β), 55Cs134m(IT) / Cs135m(IT), 56Ba141(β), 57La142(β), 59Pr144m(IT)→Pr144(β), 60Nd151(β)→61Pm151(β), 63Eu154m(IT) / 62Sm155(β) are generated by IT and β decay of , and are less than the weight after leaving untreated for 6 years respectively. In addition, 39Y90 remains until the β decay of the long-lived parent nuclide 38Sr90 disappears. The radionuclide (weight) increased due to countermeasures 3 nuclide 39Y91, 71Lu177m / 177 Although the σp is greater than 1 and the nuclide is converted by neutron irradiation for the 8th time and the weight becomes 0 g, this 3 nuclide is converted by neutron irradiation for the 9th time to produce radioactive parent nuclides 38Sr91(β) / 39Y91m(IT), 70Yb177m(IT) →Yb177(β) are generated by IT and β decay of , and are more than the weight after leaving untreated for 6 years respectively. Note that 71Lu177m / 177 is a newly generated nuclide that decays from the parent nuclide 71Yb177 generated by neutron capture of 70Yb172 / 173 as 71Yb177m(IT)→Yb177(β)→71Lu177m(β / IT)→ 71Lu177(β)→72Hf177 (stable) and decays. The radioactive insoluble nuclide generated in the soluble material tank is 50Sn117m The parent nuclide is 48Cd117m(β) with σp = 0. The weight of the daughter nuclide generated by decay increases, but the time to reach 0.1 Bq is 3.4 years. 50Sn117m does not occur in the sparingly soluble substance tank. The radioactive gaseous nuclides generated in the soluble material tank are 35Br83, 36Kr83m, 53I132 / 133, and 54Xe133m / 133, a total of 6 kinds. These nuclides decay in the following 3 ways They are generated as follows: 34Se83m (β, 70 s) → 35Br83 (β, 2.37 h) → 36Kr83m (IT, 1.83 h) → Kr83 (stable), 52Te132 (β, 3.2 d) → 53I132 (β, 2.3 h) → 54Xe132 (stable), 52Te133m (β / IT, 55.4 m) → Te133 (β, 12.5 m) → 53I133 (β, 20.8 h) → 54Xe133m (IT, 2.19 d) → Xe133 (β, 5.25 d) → 55Cs133 (stable). These six radioactive gases gradually decrease with the number of neutron irradiations, and the radioactivity of each radionuclide generated after the seventh irradiation is 0.1 Bq or less and can be ignored.

[0103] Table 2B-1 shows the results of calculating the weight of the stable nuclides in the soluble material tank after 180 days and the weight changes after leaving it untreated for 6 years and after applying the present invention. 138 stable nuclides after leaving it untreated for 6 years; weight 810.4 kg (77 soluble nuclides; 708.0 kg, 44 poorly soluble nuclides; 102.3 kg, 17 gaseous nuclides; 0 g), the number of nuclides is 44 species ( 26 species of soluble nuclides, 11 species of poorly soluble nuclides, 7 species of gaseous nuclides) due to the countermeasures, and the weight increases to 1072.2 kg ( 431.9 kg of soluble nuclides, 634.2 kg of poorly soluble nuclides, 6.1 kg of gaseous nuclides). However, the weights of these nuclides are all the weights of the nuclides alone. Note that the 11 poorly soluble nuclides generated in the soluble material tank are not generated in the poorly soluble material tank, so the weight after leaving it untreated for 6 years is described, and the weights of the 7 gaseous nuclides after leaving them for 6 years are described in the gas tank. All soluble and stable 51 nuclides not described have σp of 1 or more, The total nuclide weight of 51 stable nuclides becomes 2.1E-52 g by the 9th irradiation of cold neutrons. This is because after the 9th irradiation of cold neutrons, the parent nuclide 66Dy166 with σp = 0.91 cannot capture neutrons and 7.7E-50 g remains, and Dy166(β,3.4d)→67Ho166m(β,1200y)→68Er166 (stable) decays, and 68Er166 remains 2.1E-52 g after 6 years due to... Even when radionuclides are generated by nuclide conversion through neutron irradiation of stable nuclides, and even if there are radionuclides with a long half-life among the daughter nuclides generated during the decay process, if the σp of the nuclide is greater than 1 If it is large, in the next neutron irradiation, radioactive nuclides with a short half-life or stable nuclides it will be nuclide-converted.

[0104]

Table 2B-1

[0105] Soluble nuclides in the soluble material tank, soluble nuclides with a weight of 1E-40 g or more after countermeasures 26 For 11 insoluble nuclides and 7 gaseous nuclides generated by neutron irradiation and 3 soluble nuclides, Table 2B-2 shows the neutron capture probability σp, and the nuclide weights [unit: g] before and after countermeasures after 180 days and 6 years after nuclear fuel removal. The weight represents the value of a single nuclide. There are 3 soluble stable nuclides with σp (values shown in []) less than or equal to 1. 30Zn70 [0.93] and 34Se82 [0.4] are partially retained without nuclide conversion by neutron irradiation. For the former, no parent nuclide is generated after the second irradiation, and for the latter, there is no parent nuclide. Therefore, both are partially converted by neutron capture after 9 neutron irradiations, and their weights gradually decrease and are less than those after 6 years of leaving without countermeasures. 38Sr88 [0.05] has a large remaining weight without nuclide conversion by neutron irradiation. The weight generated by the β decay of the parent nuclide 37Rb88 (β, 17.8m) generated by the nuclide conversion of 37Rb86 / 87 in the first and second irradiations is added, and then it remains without nuclide conversion by neutron irradiation. Its weight gradually decreases but is more than that after 6 years of leaving without countermeasures. The remaining soluble stable nuclides 23 All the nuclides have σp greater than or equal to 1 and are converted by the 8th neutron irradiation with a weight of 0 g. They are converted to radioactive parent nuclides with σp of 0 or less than or equal to 1 by the 9th irradiation, and the weight of the stable soluble nuclides generated by subsequent decay shows a difference compared with that after 6 years of leaving without countermeasures. The weights that decrease due to countermeasures are 31Ga71, 55Cs133 , 56Ba134~138, 58Ce140 , 59Pr141, 60Nd142 / 145, 62Sm152 / 154, 63Eu151, 16 of 64Gd154 / 155 The nuclides for which the weight increases are 64Gd158 , 66Dy161 / 162, 67Ho165, 68Er167, 70Yb172 / 173 7 The nuclide 70Yb173 is a newly increased nuclide by neutron irradiation. The weights of stable nuclides with a mass number of 155 or more are significantly increased by the countermeasures. Since the insoluble radionuclides generated in the soluble material tank are not irradiated with neutrons, the value of σp of the soluble radioactive nuclides that become the parent nuclides is affected. The parent nuclide of 32Ge72 is 30Zn72(β)[0.095], and 32Ge72 generated by the β decay of the parent nuclide remaining without nuclide conversion by neutron irradiation decreases from the weight after 6 years of being left unaddressed. The parent nuclides of 40Zr90 are 38Sr90[0.09] and 39Y90m[0]. The weight generated by the decay of 38Sr90(β)→39Y90(β)→40Zr90(stable) remaining without nuclide conversion in each neutron irradiation is added to the weight generated by the decay of 39Y90m(IT / β)→Y90(β)→40Zr90 due to the nuclide conversion of Y89[11.1] by neutron irradiation up to 2 times, and it increases from the weight after 6 years of being left unaddressed. The remaining 9 stable insoluble nuclides have a σp of 0 for the radioactive parent nuclides. For 3 types where the parent nuclide becomes 0 g after the second neutron irradiation, the weight of 32Ge70 with 31Ga70 as the parent nuclide is more than that after 6 years of being left unaddressed, and the weight of 46Pd108 / 110 with 47Ag108 / 110 as the parent nuclide is less than that after 6 years of being left unaddressed. For the other 6 types, 32Ge73 and 40Zr91 / 92 where the parent nuclide is generated up to 9 neutron irradiations decrease from the weight after 6 years of being left unaddressed, 50Sn117 increases from the weight after 6 years of being left unaddressed, and 72Hf177 / 178 is a nuclide newly generated by neutron irradiation. There are seven stable gases generated in the soluble material tank. 2He4 is a nuclide newly generated by neutron irradiation and does not occur in the gas tank but only in the soluble material tank. This is due to the α decay of 4Be8(α, <1fs) with 3Li8(β, 0.84s), which is converted from 3Li6 / 7 by neutron capture, as the parent nuclide to produce 2He4 (stable). The parent nuclide 52Te132(β)[0.93] of 54Xe132 is converted by neutron irradiation and its weight decreases. The weight added by the β decay of 53I132(β, 2.3h) → 54Xe132 (stable) is less than the weight after leaving it unaddressed for six years. The remaining five nuclides, 35Br79 / 81, 36Kr83 / 86, and 54Xe134, have a σp of 0 for the parent nuclides, and are generated by the decay of their respective parent nuclides 34Se79m(IT / β), Se81m(IT / β), Se83m(β), 37Rb86m(IT) → Rb86(β / ec), 55Cs134m(IT) → Cs134(β / ε). Four of these nuclides, excluding 35Br81, have a weight decrease compared to the weight after leaving it unaddressed for six years.

[0106]

Table 2B-2

[0107] There are nuclides whose weight increases with stable nuclides after six years, which is due to the decay of long half-life radioactive parent nuclides shown in the brackets. For soluble nuclides, 62Sm154 and 64Gd154 [63Eu154m / 154], Gd155 [Eu155] are applicable. For insoluble nuclides, 40Zr90 [38Sr90], 40Zr91 [39Y91], 50Sn117 [Sn117m], 72Hf177 [71Lu177m / 177] are applicable. The soluble radioactive nuclides of these parent nuclides are vitrified, but the radioactive soluble nuclides strontium 38Sr90 and lutetium 71Lu177, which are insoluble and become parent nuclides of stable nuclides, are recovered as recycled radioactive nuclides. (Described later)

[0108] (Nuclides in the insoluble material tank) When applying Tables 1A and 1B to the nuclides in the insoluble material tank, the t of soluble nuclides and gas nuclides 0The future weight (column F) is 0 g. Since the soluble nuclides and gaseous nuclides generated by the radioactive decay of the insoluble nuclides after neutron irradiation are not irradiated with neutrons, the corresponding cells of G, M, · ·, AD, ··· display ⇒, and the cumulative weight after neutron irradiation is the total weight just before irradiation. The storage time t j is t 1 ’, t 2 ’, ···. In the case of the decay series of only soluble nuclides and gaseous nuclides with the same mass number, since the initial weight is 0 g, the nuclides of this mass number are excluded from the table ( 34Se78~39Y90 and 54Xe127 and later). The nuclides to be calculated are from 4Be9 to 54Xe128. The soluble nuclide 52Te128 generated by the β decay of the insoluble nuclide 51Sb128 produces the stable gaseous nuclide 54Xe128 by 2β decay. The weights of the gaseous nuclides and soluble nuclides generated in the insoluble material tank are shown in the table of the insoluble material tank.

[0109] Only the insoluble nuclides in the insoluble material tank are irradiated with neutrons Nj times. After neutron irradiation, a nitric acid solution with a specified concentration (4 mol / L in this example) is added to the insoluble material tank, and after storage for t j hours, the generated soluble nuclides are recovered to the soluble material tank B with a filtration device or the like, and after the next neutron irradiation, the soluble nuclides and nitric acid solution in the soluble material tank B are refluxed to the insoluble material tank Nj times. In this example, the number of irradiations Nj is set to 13 times to minimize the weight of the vitrified body in the insoluble material tank, and the storage period t j is t 1 ~t 12 is 30 days, t 13 is 190 days (equivalent to 2 years in total from the removal of nuclear fuel), and t s ’ is 4 years. The nitric acid solution with a concentration of 4 mol / L required to dissolve the generated soluble nuclides increases by 5 L, 30 L, 70 L, 75 L, ··· for each neutron irradiation, and the maximum is about 100 L. Based on Table 1A and Table 1B, when neutrons were irradiated on the sparingly soluble nuclides in the sparingly soluble material tank under the aforementioned conditions, the change in the weight of the nuclides changed by decay was calculated using an Excel worksheet. The sparingly soluble solids in the sparingly soluble material tank are 133 types (86 radioactive nuclides and 47 stable nuclides), and the weight 180 days after nuclear fuel removal is 763.4 kg for the sparingly soluble nuclides (235.9 kg for radioactive nuclides and 527.4 kg for stable nuclides). All these weights are the weights of individual nuclides.

[0110] Regarding the sparingly soluble nuclides in the sparingly soluble material tank, Table 3A-1 shows the calculation results of the weight [unit: g] and radioactivity [unit: Bq] after 6 years when compared with the weight 180 days after spent nuclear fuel removal, when left untreated for 6 years, and when the present invention was applied (neutrons were irradiated on only soluble nuclides under the aforementioned conditions). After leaving untreated for 6 years, the number of sparingly soluble radioactive solid nuclides is 90 types with a weight of 234.0 kg (including the weight of 6.16 kg of 4 non-soluble radioactive nuclides that do not occur in the soluble material tank after 6 years of no countermeasures). Through countermeasures, the number of nuclides decreases to 12 types with a weight of 31.3 kg (4 soluble nuclides with 58.3 g, 8 sparingly soluble nuclides with 31.2 kg, and no gaseous nuclides). All these weights are the weights of individual nuclides and not the weights of compounds such as oxides and nitrates. Through countermeasures, the radioactivity decreases to 2.36 TBq (T is tera) for available nuclides and 0.15 TBq for sparingly soluble nuclides. There are 78 types of unlisted radioactive sparingly soluble nuclides. Among them, for 15 types of sparingly soluble nuclides with a half-life of 50 days or more, all have σp of 1 or more. For 10 types including 40Zr93 / 95, 41Nb92, 42Mo100, 43Tc98, 44Ru106, 45Rh102, 50Sn119m / 121m / 123, there is no parent nuclide. For 41Nb93m / 95, the parent nuclide is the radioactive sparingly soluble nuclide 40Zr93 / Zr95 with σp greater than 1. Therefore, these 12 nuclides are converted by nuclide conversion in the first neutron irradiation and become 0 g. For 3 daughter nuclides 41Nb94, 43Tc99, 49In115 with a long half-life but σp of 0 for the parent nuclide, through nuclide conversion by the second neutron irradiation, no parent nuclide is generated and the weight of the daughter nuclide becomes 0 g. The two nuclides, 45Rh106 and 50Sn121, with short half-lives have parent nuclides 44Ru106 (β, 371.8 d) and 50Sn121m (IT / β, 43.9 y) with long half-lives. However, σp is 1.12 and 8.52 respectively. In the first neutron irradiation, the parent nuclides are converted into nuclides with a mass of 0 g, and the weight of their daughter nuclides becomes 0 g. The remaining 61 nuclides have short half-lives and their weight becomes 0 g after 6 years. The 168.8 kg of insoluble radionuclides that existed 180 days after the removal of nuclear fuel become 0 g through countermeasures. The gas generated with the insoluble radioactive substance as the parent nuclide in the insoluble substance tank is only stable 53I127, and no radioactive gas is generated. Among the decay series of nuclides with the same mass number Z, the daughter nuclides generated by the decay of insoluble nuclides are only soluble nuclides, and no gaseous nuclides are directly generated. There are two decay series in which the parent nuclide is an insoluble nuclide and a gaseous nuclide is generated, namely 32Ge → 33As → 34Se → 35Br → 36Kr and 49In → 50Sn → 51Sb → 52Te → 53I → 54Xe. The radionuclides may include nuclear isomers. The mass numbers are 79 - 88 for the former and 127 - 134 for the latter. For the former, the half-life of Ge79 - 88 is less than 30 seconds and it does not exist 180 days after the removal of nuclear fuel, and no gaseous bromine or krypton is generated. For the latter, 51Sn127m and 52Sb128 are generated by neutron irradiation. In the 127 series, the decay ends at 53I127 (stable), and in the 128 series, the decay ends at 52Te128 (2β, 7.7E+24 y) → 54Xe128 (stable), and no radioactive gas is generated. Also, for mass numbers of 129 and above, no insoluble nuclides are generated, and in this decay series, gaseous nuclides are generated only when the mass numbers are 127 and 128.

[0111]

Table 3A-1

[0112] For nuclides with a weight of 1E-40 g or more after countermeasures against radionuclides in the insoluble substance tank, Table 3A-2 shows the calculation results of the changes in weight and radioactivity when left unaddressed for 6 years and when the present invention is applied. The table shows the decay mode and half-life of the radionuclides generated in the insoluble substance tank, the neutron capture probability σp (0.353 meV), the nuclide weight [unit: g], and the radioactivity [unit: Bq]. Note that the weight is the weight of the nuclide alone, not the weight of compounds such as oxides and nitrates.

[0113]

Table 3A-2

[0114] Among the radioactive insoluble nuclides generated in the insoluble substance tank, the radioactivity of 40Zr96 and 51Sb124 becomes 0.1 Bq or less 6 years after countermeasures, and the radioactivity of 4Be10, 46Pd107, 50Sn126, 51Sb125 / 126m / 126 becomes 0.1 Bq or more. The nuclides with reduced radioactivity due to countermeasures are 40Zr96, 46Pd107, 50Sn126, 51Sb124 / 125 / 126m / 126, a total of 7 nuclides, and the nuclide with increased radioactivity is 4Be10. Among the 7 nuclides with reduced radioactivity (weight) due to countermeasures, 40Zr96 and 50Sn126 have σp values of 0.183 and 0.62 respectively and no parent nuclides. Their half-lives are long, and part of them remains without nuclide conversion under neutron irradiation, and the remaining weight decreases with the number of irradiation times. 46Pd107, 51Sb124, and Sb125 have σp values greater than 1 and are converted into nuclides by 13 neutron irradiations, and the weight becomes 0 g. They are generated by the decay of the radioactive parent nuclides 44Ru107(β), 51Sb124m(IT / β), and 50Sn125m(β) converted into nuclides by the 13th neutron irradiation, but are less than the weight after being left for 6 years respectively. Also, for 51Sb126m / 126, since the σp of the parent nuclide 51Sn126(β) is 0.62 and the half-life is long, it remains without nuclide conversion under 13 neutron irradiations and remains until the β decay of the parent nuclide disappears, but is less than the weight after being left for 6 years respectively. There is one nuclide whose weight has increased as a countermeasure. There is no parent nuclide of \(^{10}_{4}Be\) with an extremely small \(\sigma_p\). The radioactive nuclide \(^{10}_{4}Be(\beta)\) generated by the nuclide conversion of stable \(^{9}_{4}Be\) with \(\sigma_p = 0.338\) through 13 neutron irradiations has a slightly increased weight compared to its weight after being left for 6 years. The only radioactive soluble nuclide remaining in the insoluble material tank after 6 years is tellurium, which is the four nuclides \(^{125m}_{52}Te\), \(^{128}_{52}Te\), and \(^{127m / 127}_{52}Te\). The parent nuclides of the first two are \(^{125m}_{50}Sn(\beta)\) and \(^{128}_{51}Sb(\beta)\) with \(\sigma_p = 0\), which are generated by the beta decay of the parent nuclides converted through 13 neutron irradiations, and their weights gradually decrease with the number of irradiations. After 6 years, they are separated from the parent nuclides in the insoluble material tank, so the time to reach \(0.1 Bq\) of \(^{125m}_{52}Te\) is 3.1 years, and it decays to stable \(^{125}_{52}Te\). Also, \(^{128}_{52}Te\) is a long-lived nuclide and its weight decreases compared to its weight after being left uncountered for 6 years with countermeasures. The parent nuclides of the latter two are \(^{127m}_{50}Sn\) with \(\sigma_p = 0\), and \(^{127m}_{50}Sn(\beta, 4.13m)\) generated by the nuclide conversion of \(^{126}_{50}Sn\) with \(\sigma_p = 0.62\) through 13 neutron irradiations decays as \(^{127}_{51}Sb(\beta, 3.85d) ightarrow ^{127m}_{52}Te(IT / \beta, 106.1d) ightarrow ^{127}_{52}Te(\beta, 9.35h) ightarrow ^{127}_{53}I\) (stable) and changes to stable gaseous \(^{127}_{53}I\) after about 19 years. Note that tellurium does not occur in the soluble material tank. There are no radioactive gaseous nuclides generated in the insoluble material tank.

[0115] Table 3B - 1 shows the results of calculating the weight of the stable nuclides in the insoluble material tank after 180 days and the weight changes when left uncountered for 6 years and when the present invention is applied. Stable solid nuclides after being left uncountered for 6 years 95 Species; Weight 444.0 kg (soluble nuclides are 31 species; 7.57 kg, insoluble nuclides are 47 species; 436.4 kg, gaseous nuclides are 17 species; 0 g) is reduced to 24 species (12 soluble nuclides, 11 insoluble nuclides, 1 gaseous nuclide) by countermeasures, and the weight increases to 732.1 kg (718.1 kg of soluble nuclides, 12.6 kg of insoluble nuclides, 1.41 kg of gaseous nuclides). However, the weights of these nuclides are all the weights of single nuclides. All of the undisclosed sparingly soluble stable nuclides with 36 nuclides have a σp of 1 or more. They are converted into other nuclides by neutron irradiation and their weight becomes 0 g. Even if the radioactive nuclide that becomes the parent nuclide after nuclide conversion has a long half-life, it becomes a sparingly soluble nuclide with a σp greater than 1 and is converted into other nuclides by neutron irradiation and its weight becomes 0 g. For example, stable 49In113 is converted into other nuclides by the first neutron irradiation and decays as 49In115m(IT / β,4.5h)→In115(β,4.4E+14y)→50Sn115(stable). In115 with a σp greater than 1 is converted into In116m by the second neutron irradiation and its weight becomes 0 g. 49In116m(β,54.3m)→50Sn116(stable) decays and the weight of In113 becomes 0 g, while the weight of stable 50Sn116 increases. However, the σp of this nuclide is 0.9 and its weight decreases with the number of neutron irradiations. Also, stable 46Pd108 is converted into other nuclides by neutron irradiation and decays as 46Pd108+1n→Pd109m(IT,4.7m)→Pd109(β,13.6h)→47Ag109m(IT,39.8s)→Ag109(stable). The weight of Pd108 becomes 0 g and the weight of stable soluble nuclide 47Ag109 increases.

[0116]

Table 3B-1

[0117] Table 3B-2 shows the neutron capture probability σp(0.353 meV), the nuclide weights [unit: g] 180 days after fuel removal, 6 years after leaving without countermeasures, and after countermeasures, for 11 stable sparingly soluble nuclides with a weight of 1E-40 g or more after countermeasures, 12 stable soluble nuclides generated by neutron irradiation, and 1 gaseous nuclide. All 11 insoluble stable nuclides have weights after 6 years of countermeasures that are less than their weights after 6 years of being left untreated. There are 7 nuclides with σp of 1 or less (the values of σp are shown in []). Among them, for 4 nuclides, 4Be9[0.34], 40Zr90[0.09], Zr94[0.42], 50Sn124[0.94], since there are no parent nuclides, the weight gradually decreases with the number of neutron irradiations. For the other 3 nuclides 50Sn114[0.92] / Sn116[0.91] / Sn122[0.98], part of them remains without being converted by neutron irradiation. After the second neutron irradiation, the respective parent nuclides 49In114(β / ε), 49In116m(β), 51Sb122m(IT)→Sb122(β / ε) do not occur, so the weight of the daughter nuclides becomes 0 g. At the 13th neutron irradiation, part of them is converted by neutron capture, and the weight of the remaining daughter nuclides decreases and is less than that after 6 years of being left untreated. The remaining 4 nuclides 42Mo97 / 98 and 44Ru101 and 51Sb123 have σp of 1 or more and are converted into 0 g by 13 neutron irradiations. However, the weights of the daughter nuclides generated by the β decay of the parent nuclides 40Zr97(β) / 98(β) and 42Mo101(β) and 50Sn123m(β) are less than those after 6 years of being left untreated. Do not irradiate neutrons to the 12 soluble nuclides generated in the insoluble material tank. Among them, for 4 nuclides, 31Ga71, 33As75, 34Se77, 48Cd114, the σp of their respective parent nuclides 32Ge71m(IT)→Ge71(ec), 32Ge75m(IT), 32Ge77m(β / IT), 49In114m(IT / ε) is 0, the generation of parent nuclides by neutron irradiation is up to 3 times, and the weights of the generated daughter nuclides are less than those after 6 years of being left untreated. 52Te125 is generated by the decay of the parent nuclide 50Sn125m(β) that occurs by nuclide conversion every time during 13 neutron irradiations, and its weight gradually decreases with the number of irradiations and is less than that after 6 years of being left untreated. For the remaining 7 nuclides, 5B10, 47Ag107 / 109, 48Cd111, 52Te122 / 124 / 126, the σp of their respective parent nuclides 4Be10(β), 44Ru107(β), 46Pd109m(IT), 46Pd111m(IT / β), 51Sb122m(IT) / 124m(IT / β) / 126m(β / IT) is 0, and they are generated by the β and IT decays of the parent nuclides generated by 13 neutron irradiations. The weights of these daughter nuclides are more than those after 6 years of being left untreated. The stable nuclide generated in the insoluble material tank is only 1.41 kg of 53I127, which is due to the decay of 50Sn127m(β) converted into a nuclide by neutron capture as the parent nuclide, 51Sb127(β, 3.85 d) → 52Te127m(IT / β, 106.1 d) → 52Te127(β, 9.35 h) → 53I127(stable). After confirming safety with a radiation dose monitor, it can be released. In addition, after 6 years of countermeasures, the radioactive tellurium generated in the soluble tank B attached to the insoluble material tank decays as 52Te127m(IT / β, 106.1 d) → Te127(β, 9.35 h) → 53I127(stable), and 0.63 mL (3.35 mg) of I127 is generated at 20 °C. Therefore, when solidifying tellurium into glass, silver is added and solidified as silver iodide. There are nuclides with an increasing weight as stable nuclides after 6 years of countermeasures〔〕, which are due to the decay of long-lived radioactive parent nuclides shown inside, not insoluble nuclides, but soluble nuclides such as 5B10〔4Be10〕, 47Ag107〔46Pd107〕, 52Te124〔51Sb124m〕, 52Te125〔51Sb125〕are applicable. The insoluble radioactive nuclides of these parent nuclides are solidified into glass. However, 46Pd107 with a large σp exists alone in the nuclide separation after 6 years as will be described later, so it is converted into a nuclide by thermal neutron irradiation and can be recovered by decaying into stable Ag109 after 41.2 days through 46Pd109m(IT, 3.1 s) → Pd109(β, 13.59 h) → 47Ag109m(IT, 39.8 s) → Ag109(stable).

[0118]

Table 3B-2

[0119] (Nuclides in the gas tank) When applying Table 1A and Table 1B to the nuclides in the gas tank, the t of soluble and insoluble nuclides 0 The weight (F column) after a certain number of days is 0 g. Since neutrons are not irradiated to the solid nuclides and gas nuclides generated by the radioactive decay of gas nuclides, ⇒ is displayed in the cells of column G and column M corresponding to these nuclides, and the cumulative weight after neutron irradiation is the weight immediately before irradiation. In the gas tank, the gas nuclides generated in the soluble material tank and the insoluble material tank are ColdRecover it immediately before neutron irradiation. After leaving the gaseous tank for a certain period (t 0 hours) after the removal of nuclear fuel, only iodine in the iodide tank separated by liquefaction from the gaseous tank is irradiated with thermal neutrons only once. Therefore, it corresponds to an iodine nuclide with σp of 1 or more. G In the column cell, +n is displayed, corresponding to an iodine nuclide with an unlisted σp whose mass number has increased by nuclide conversion. G In the column cell, the nuclide with the mass number before nuclide conversion and the number of captured neutrons are displayed within <>. Note that since iodine is irradiated with thermal neutrons, the σp of the gaseous nuclide uses the value at a neutron energy of 0.0253 eV. Since iodine is irradiated with thermal neutrons, the σp of the gaseous nuclide uses the value at a neutron energy of 0.0253 eV. Iodine 53I127 (stable), I128 (β / IT, 25m), I129 (β, 1.57E+7y) with σp of 1 or more each capture 3 to 1 neutrons by neutron irradiation to become I130m (IT / β, 8.84m), and I130 (β, 12.4h) and I131 (β, 8.03d) each capture 2 and 1 neutrons respectively and are nuclide-converted to I132 (β, 2.30h). In the case of only soluble and insoluble nuclides with the same mass number, since the initial weight is 0 g, the nuclides of this mass number are excluded from the table (nuclides from 29Cu66 to 34Se78, 37Rb87 to 52Te126, and nuclides after 54Xe137). The nuclides to be calculated are from 1H3 to 54Xe137.

[0120] In the gas tank, after leaving it for a certain period (t 0 hours) after removing the spent nuclear fuel Including gaseous nuclides recovered from the soluble and insoluble tanks , heat the gas tank to sublimate and vaporize bromine and iodine, cool the iodine receiver at the upper part of the gas tank to a temperature above the boiling point of bromine with a cooling device to liquefy only iodine and take it out, transfer it to an iodide tank, and irradiate only iodine with thermal neutrons for nuclide conversion. In this example, t 0 is 180 days. The standing period t S after the final thermal neutron irradiation is 6 years including 180 days from the removal of used nuclear fuel. Based on Table 1A and Table 1B, after irradiating only the iodine in the gas tank with neutrons under the aforementioned conditions, the change in the weight of the nuclide changed by decay was calculated using an Excel worksheet. The weights of the gaseous nuclides generated in the soluble and insoluble tanks are not included in the gas tank. The gas tank contains 47 nuclides (30 radioactive nuclides and 17 stable nuclides). The weight 180 days after removing the nuclear fuel is 385.4 kg (158.1 kg of radioactive nuclides and 227.3 kg of stable nuclides). All of these weights are the weights of gaseous nuclides only.

[0121] Regarding the radioactive nuclides in the gas tank, Table 4A-1 shows the results of calculating the changes in weight [unit: g] and radioactivity [unit: Bq] 6 years after removing the spent nuclear fuel (weight 180 days later), after leaving it untreated for 6 years, and after applying the present invention (irradiating only iodine with neutrons under the aforementioned conditions). Among the 32 radioactive gaseous nuclides with a weight of 157.5 kg after leaving it untreated for 6 years, the number of nuclides 8 decreases to [number of nuclides] with a weight of 146.0 kg due to the countermeasures. All of these weights are the weights of individual nuclides. The radioactivity remains unchanged at 22.1 PBq (P is peta) due to the countermeasures. There are 24 radioactive gaseous nuclides not described, which amount to 114.8 kg after leaving it untreated for 6 years, but the weight of the nuclides becomes 6.56×10 -55 g due to the countermeasures. This is because 0.695 mg of 54Xe131m decays to Xe131 (stable) through Xe131m(IT,11.8d)→Xe131, and 6.56E-55 g of 54Xe131m remains after 6 years. Among the 8 radioactive iodine nuclides, 3 nuclides of 53I129 / 131 / 132 have a weight of 1E-40 g or more 180 days after removing the spent nuclear fuel. 11.48 kg of 53I129(β,15.7 million years)[σp24.2] 180 becomes 0 g due to nuclide conversion by the first thermal neutron irradiation after the removal date, and 53I130m(IT / β,8.84m) generated by the nuclide conversion decays to 54Xe130 (stable) through I130(β,12.4h)→54Xe130 37.5 after [number of days] of neutron irradiation, and is nuclide-converted to 11.48 kg of stable 54Xe130. 93 μg of I131(β,8.03d)[σp63.2] is nuclide-converted by neutron irradiation and becomes 0 g in weight, and 0.1 fg of 53I132(β,2.3h)[σp0] has 93 μg generated by neutron capture of I131 added, and 4.6It will become 54Xe132 (stable) in the future. Among the other five, 53I128 / 130 / 130m / 133 / 134 have short half-lives and will disappear within 180 days. The remaining 16 radioactive gas species other than the above have short half-lives of 10 days or less and do not irradiate neutrons, so they decay into stable nuclides by radioactive decay, and the weight of all 16 nuclides becomes 0 g. The reason for not irradiating neutrons to gas nuclides other than iodine is that 10% of 54Xe136 (2β, 2.2E+21y) [σp0.1] present in large amounts is converted into nuclides by thermal neutron irradiation, and 54Xe137 (β, 3.8m) → 55Cs137 (β, 30.1y) → 56Ba137m (IT, 2.6m) → 56Ba137 (stable) decay occurs, and a large amount of the long-lived radioactive nuclide 55Cs137 is generated during this decay process. The radioactive gas nuclides recovered from the soluble material tank are 35Br83, 36Kr83m, 53I132 / 132m / 133, 54Xe133m / 133 7 species, and these nuclides are generated by the following three decays of radioactive soluble nuclides converted by neutron irradiation. 34Se83m (β) → 35Br83 (β) → 36Kr83m (IT) → 36Kr83 (stable), 52Te132 (β) → 53I132m (IT / β) → I132 (β) → 54Xe132 (stable), 52Te133m (IT / β) → 52Te133 (β) → 53I133 (β) → 54Xe133m (IT) → 54Xe133 (β) → 55Cs133 (stable). The weight of the generated radioactive gas nuclides gradually decreases with the number of neutron irradiations, and countermeasures Within 2 years, it is 0.1 Bq or less are taken. No radioactive gas nuclides are generated in the insoluble material tank. There are no radioactive gas nuclides recovered from the insoluble material tank, but when radioactive gas is generated when the generation status of FP of used nuclear fuel differs depending on the operating conditions of nuclear power generation, irradiation time, etc. or when MOX fuel is used, etc., it is recovered in the gas tank and the measures shown in the examples are taken.

[0122]

Table 4A-1

[0123] For nuclides with a weight of 1E-40 g or more after countermeasures against radionuclides in the gas tank, Table 4A-2 shows the calculation results of the changes in weight and radioactivity when left unaddressed for 6 years and when the present invention is applied. The table shows the decay mode, half-life, neutron capture probability σp (0.0253 eV), nuclide weight [unit: g], and radioactivity [unit: Bq] of the radionuclides generated in the poorly soluble substance tank. Note that the weight is the weight of the nuclide alone.

[0124]

Table 4A-2

[0125] Radioactive gas generated in the gas tank 8 For the nuclides, the weight and radioactivity after 6 years of countermeasures are almost the same as those after 6 years of being left unaddressed. After 6 years of countermeasures, the nuclides with a radioactivity of 0.1 Bq or less are 4 types: 54Xe127 / 129m / 131m / 136, and the nuclides with a radioactivity of 0.1 Bq or more are 4 types: 1H3, 6C14, 36Kr81 / 85. Note that 6C14 exists as an oxide gas. 54Xe136 (2β, 2.165E+21y) with a small σp has no effect of countermeasures, but its radioactivity is as small as 6.5 mBq and it is a nuclide with a natural abundance ratio of 8.86%. There are no radioactive solid nuclides generated in the gas tank.

[0126] Regarding the stable nuclides in the gas tank, Table 4B-1 shows the calculation results of the weight after 180 days and the weight changes when left unaddressed for 6 years and when the present invention is applied. After 6 years of being left unaddressed, there are 17 stable gas nuclides with a weight of 227.3 kg. Due to the countermeasures, the number of nuclides becomes 18, with a weight of 248.0 kg (2 soluble nuclides with a weight of 1.74k g, no poorly soluble nuclides, and 16 gas nuclides; 246.2 kg). Increase The weight of the stable gas nuclides has increased slightly. However, the weights of these nuclides are all the weights of the nuclides alone. The stable soluble nuclides generated in the gaseous tank are 623.3 g of 37Rb85 and 38.6 ng of 55Cs133. However, 1.115 kg of Cs133 generated by the decay of gaseous 53I133, 54Xe133, etc. recovered from the soluble tank is added to the solid tank attached to the gaseous tank. Note that no stable insoluble nuclides are generated in the gaseous tank. One unlisted stable gas nuclide is \(^4_2He\), which does not occur in the gas tank and only occurs in the soluble material tank during the first neutron irradiation, so it is not described here.

[0127]

Table 4B-1

[0128] For 16 stable gas nuclides with a weight of \(1\times10^{-40}\ g\) or more after countermeasures and 2 soluble stable nuclides generated by neutron irradiation, the neutron capture probability \(\sigma_p\) (for gas, \(0.0253\ eV\); for solid, \(0.353\ meV\)), the nuclide weights [unit: g] 180 days after nuclear fuel removal, 6 years after leaving unaddressed, and after countermeasures are shown in Table 4B-2.

[0129]

Table 4B-2

[0130] By the countermeasure of irradiating only iodine with thermal neutrons, the weights that increased compared to those after 6 years of leaving unaddressed for stable gas nuclides are There are two types, 54Xe130 and 2He3. For the former, 2.6 kg of 53I127 (stable) and 11.5 kg of 53I129 (β, 1.57E+7y) with large σp are converted into nuclides, and 53I130m (IT / β, 8.84m) → I130 (β, 12.36h) → 54Xe130 (stable) decays, increasing by 14.1 kg. For the latter, it slightly increases due to the β decay of the radioactive nuclide 1H3. Eleven stable gas nuclides, \(^{14}_7N\), \(^{81}_{35}Br\), \(^{80 / 82 / 83 / 84 / 86}_{36}Kr\), \(^{128 / 131 / 132 / 134}_{54}Xe\), do not undergo thermal neutron irradiation, so their total weight does not change and remains at \(224.3\ kg\) from 6 years after spent nuclear fuel removal. The remaining three, \(^{79}_{35}Br\), \(^{127}_{53}I\), \(^{129}_{54}Xe\), are decreasing compared to their weights after 6 years of leaving unaddressed. 35Br79 has a large σp parent nuclide 34Se79 (β, 3.3E+5y) is irradiated with cold neutrons in the soluble tank and decays, and the daughter nuclide 35Br79 is not generated. Therefore, 53I127 is converted into nuclides by neutron irradiation, and the parent nuclide becomes trace 54Xe127 (ec). 54Xe129 is converted into nuclides by neutron irradiation of the parent nuclide 53I129, and the parent nuclide becomes trace 54Xe129m. There are gas nuclides whose weights increase as stable nuclides after 6 years. This is due to the decay of long-half-life radioactive gas parent nuclides shown in (). The corresponding ones are \(^3_2He\) [\(^3_1H\)], \(^{14}_7N\) [\(^{14}_6C\)], \(^{81}_{35}Br\) [\(^{81}_{36}Kr\)]. The weights of the stable soluble nuclides generated in the gas tank are 623.3 g of 37Rb85 and 38.6 ng of 55Cs133, which are generated by the β decay of radioactive gases. The parent nuclides are 36Kr85 (β, 10.74 y) with a long half-life for the former and 54Xe133 (β, 5.25 d) for the latter. These are recovered in the solid tank attached to the gas tank, and the weight of the former continues to increase even after 6 years. Also, no stable insoluble nuclides are generated in the gas tank. Note that 1.115 kg of 55Cs133 is generated by the decay of the gaseous 53I133 and 54Xe133(m) recovered from the soluble material tank. The seven stable gaseous nuclides transferred from the soluble material tank are 2He4, 35Br79 / 81, 36Kr83 / 86, 54Xe132 / 134, and the weight is 6.06 kg. After 6 years of countermeasures, the weight does not increase. The stable gas 53I127 generated by the decay of 52Te127m / 127 remaining in the soluble material tank B attached to the insoluble material tank increases even after 6 years, which is as described in the treatment in the insoluble material tank.

[0131] 180 days after the spent nuclear fuel is removed, the soluble nuclides in the soluble material tank are irradiated with cold neutrons 9 times at 30-day intervals, and the generated insoluble nuclides and gaseous nuclides are not irradiated with cold neutrons. Similarly, the insoluble nuclides in the insoluble material tank are irradiated with cold neutrons 13 times at 30-day intervals, and the generated soluble nuclides and gaseous nuclides are not irradiated with cold neutrons. In the gas tank, when the fuel is removed 180 If measures are taken to irradiate only iodine with thermal neutrons once after the spent nuclear fuel is removed from each tank, the nuclides with a 0.1 Bq arrival time (the content in the brackets indicates before countermeasure → after countermeasure) of more than 10 years among the radioactive nuclides remaining 6 years after the spent nuclear fuel is removed from each tank and the long-lived nuclides with a radioactivity of 0.1 Bq or less are summarized. The soluble nuclides in the soluble material tank are 38Sr90 〔1748 years → 1736 years〕, 39Y90 〔1748 years → 1736 years〕 / 91 〔10 years → 15 years〕, 62Sm151 〔4766 years → 2926 years〕, 63Eu154 〔486 years → 329 years〕 / 155 〔202 years → 237 years〕, 7 1Lu177m 〔※ → 31.3 years〕 / 177 〔※ → 20.68 species in [year], and long-lived 48Cd116 (11000000000 years → 55.8 μBq), 58Ce142 (52300000000000 years → 5.2f Bq), 60Nd144 (33600000000000 years → 0.03f Bq), and 3 species. The time to reach 0.1 Bq of the poorly soluble 1 nuclide 50Sn117m is 3.4 years. The poorly soluble nuclides in the poorly soluble substance tank are 6 species: 4Be10 [39.5 million years → 39.8 million years], 46Pd107 [270 million years → 260 million years], 50Sn126 [9.79 million years → 5.61 million years], 51Sb125 [158 years → 25 years] / 126m [9.79 million years → 5.61 million years] / 126 [9.79 million years → 5.61 million years], and the long-lived 40Zr96 [35670000000000 years → 82.9 mBq]. The soluble nuclides are 2 species: 52Te127m [17 years → 19 years] / 127 [17 years → 19 years], and the long-lived 52Te128 (83 nBq → 0.78 nBq). The gaseous nuclides in the gas tank are 4 species: 1H3 [659 years → 658 years], 6C14 [180000 years → the same year], 36Kr81 [4710000 years → the same year] / 85 [628 years → the same year], and the long-lived 54Xe136 (6.5 mBq → the same Bq). No radioactive soluble and poorly soluble nuclides are generated. The effects of the present invention on these 8 soluble nuclides, 6 poorly soluble nuclides, and 5 gaseous nuclides are limited. However, 3 long-lived soluble nuclides and 1 poorly soluble nuclide have decreased significantly compared to their weights after 6 years of being left unaddressed, and the effect of the countermeasure is remarkable.

[0132] In the present invention, the generated high-level radioactive waste is separated and stored into a soluble substance soluble in nitric acid and an insoluble substance that is hardly soluble or insoluble. For the former, neutrons are not irradiated to the stable insoluble substance generated by decay, and for the latter, neutrons are not irradiated to the stable soluble substance generated by decay. Therefore, the recovery amount of stable nuclides is significantly increased compared to the case without tank separation. Further, in order to minimize the weight of the glass solidified body of high-level radioactive waste, the daughter nuclides generated by the radioactive decay of the parent nuclides converted by nuclide conversion are reduced using the number of neutron irradiations and the subsequent storage period as parameters, and the weight of stable nuclides is increased. As a result of calculation by changing the neutron irradiation interval from 3 days to 1 year, it is set to 30 days. The number of neutron irradiations is such that in the soluble substance tank, when the number of neutron irradiations is increased, the radioactivity of the radionuclide 55Cs134 / 135 is 2.35 μ Bq / 18.9n Bq at 8 irradiations and 0.26 nBq / 2.1p Bq at 9 irradiations, and the radioactivity of the radionuclide 71Lu177m / 177 is 7.9 PBq / 1.7 PBq at 8 irradiations and 38.2 PBq / 8.1 PBq at 9 irradiations, but since the latter is a reusable nuclide, it is set to 9 times in the examples. In the insoluble substance tank, for 40Zr96 (2β, 3.9E+19y) with σp of 0.18, the weight after 6 years without countermeasures is 53.4 kg, and it is reduced to 28.5 kg by 12 neutron irradiations, and the radioactivity is also reduced to 0.1 Bq or more. However, by 13 irradiations, the weight of this nuclide can be reduced to 23.5 kg and the radioactivity to 83 mBq. In this example, the number of irradiations is set to 13 times. So far, the nuclides remaining with a nuclide weight of 1E-40 g or more in each tank after 6 years due to countermeasures have been described. However, for the nuclides existing after 6 years of leaving without countermeasures, in order to evaluate the effect of the implementation of the present invention, Table 5-1 and 5-2 summarize the radionuclides with a 0.1 Bq arrival time of 10 years or more and the long-lived radionuclides with a radioactivity of 0.1 Bq or less for each tank. The table shows the radionuclide, decay mode, half-life, neutron capture probability, weight [unit: g] after 6 years generated in each tank without countermeasures and with countermeasures, radioactivity [unit: Bq] without countermeasures and after 6 years of countermeasures, and the 0.1 Bq arrival time.

[0133] 〔Table 5.1〕~〔Table 5.2〕 TIFF0007691459000036.tif13792TIFF0007691459000037.tif13790

[0134] For 46 long-lived radionuclides with a half-life of 50 days or more and a 0.1 Bq arrival time of 10 years or more without countermeasures, and 10 daughter nuclides with a short half-life but a long half-life of the parent nuclide, by means of neutron irradiation, the radioactivity of 53 nuclides except 53Te125m〔9.1 years〕will be 0 Bq after 6 years. The long-lived radioactive soluble nuclides with a long half-life are 30 types including 34Se79, 37Rb87, 47Ag108m / 110m, 48Cd109 / 113m / 113, 52Te123m / 125, 55Cs134 / 135 / 137, 56Ba133, 57La138, 58Ce139 / 144, 60Nd150, 61Pm146 / 147, 62Sm146 / 147 / 148, 63Eu150 / 152, 64Gd152 / 153, 65Tb160, 67Ho166m, 69Tm170 / 171. The daughter nuclides with a short half-life but a long half-life of the parent nuclide are 6 types including 47Ag108 / 109m / 110, 56Ba137m, 59Pr144m / 144. The 3 long-lived radioactive nuclides Te123 / 128 / 130, although below 0.1 Bq, will be almost 0 g and the radioactivity can be ignored 180 days after the removal of spent nuclear fuel. The long-lived radioactive insoluble nuclides with a long half-life are 16 types including 40Zr93 / 95, 41Nb92 / 93m / 94 / 95, 42Mo100, 43Tc98 / 99, 44Ru106, 45Rh102, 49In115, 50Sn119m / 121m / 123 / 126. The daughter nuclides with a short half-life but a long half-life of the parent nuclide are 4 types including 45Rh106, 50Sn121, 51Sb126m / 126. For the 3 types of 50Sn126 with a long half-life and a σp of 0.62 without countermeasures and the short-lived 51Sb126m / 126 with this as the parent nuclide, the weight of 50Sn126 without countermeasures after 6 years is 1.41 kg, which will be reduced to 4.87 mg by countermeasures. The 0.1 Bq arrival time will be reduced from 9.79 million years but is still as long as 5.61 million years.

[0135] After 180 days of spent nuclear fuel removal, the soluble material tank was repeatedly irradiated with cold neutrons 9 times at 30-day intervals, and the insoluble material tank was irradiated 13 times. After that, the solid nuclides generated by the decay of radionuclides by 6 years were recovered in the soluble material tank (including the insoluble nuclides in the insoluble material tank A and the soluble nuclides generated in the solid tank attached to the gas tank), and the insoluble material tank (including the soluble nuclides in the soluble material tank B). The recovered nuclides and nitric acid solution in the former were transferred to chloride tank 1, and the recovered nuclides and nitric acid solution in the latter were transferred to chloride tank 2, and heated separately to drive out nitric acid to make the nuclides into oxides. These generated oxide nuclides are separated by elements using the difference in boiling points, but the boiling points of these oxides are extremely high, and they are converted to chlorides with lower boiling points from the perspective of energy conservation. In this example, the oxides transferred to chloride tanks 1 and 2 after 6 years are based on the nuclide weights (both are the weights of nuclides alone, not the weights of oxides) generated in the soluble material tank, the solid tank attached to the gas tank, and the insoluble material tank, respectively 1090.1 kg and 1.738k g and 762.0 kg. To make these into chlorides, in chloride tank 1, except for the nuclide weights of germanium, zirconium, palladium, and hafnium that are not chlorinated with hydrochloric acid 624.4 kg, in chloride tank 2, except for 38.6 kg of the nuclide weights of boron, zirconium, ruthenium, and palladium that are not chlorinated with hydrochloric acid, 50 L and 40 L of 6 mol / L hydrochloric acid solution were added to 723.4 kg respectively to make chlorides. For the nuclides that are not chlorinated with hydrochloric acid, for the nuclides in chloride tank 1 465.7 kg and the nuclides in chloride tank 2 624.4 kg, chlorine gas (converted to 1 atm, 20 °C) was injected at 180 m 38.6 and 15 m 3 respectively to convert them into chlorides. When using chlorine gas, an appropriate amount of carbon is added. 3 Due to the countermeasures, there are 48 solid nuclides with a weight of 1E-40 g or more in the soluble substance tank, 35 in the insoluble substance tank, and 2 in the gas tank. These nuclides are arranged in ascending order of the boiling point of chloride for each tank, and the nuclide, decay mode, half-life, neutron capture probability σp, boiling point of chloride [unit: °C], weight [unit: g] of the tank after 6 years without countermeasures and after countermeasures, radioactivity [unit: Bq] before and after countermeasures, and the time to reach 0.1 Bq before and after countermeasures are summarized in Tables 6.1 to 6.3. Note that the nuclide weight is the weight of the nuclide itself, not the chloride.

[0136]

Table 6-1

Table 6-2

Table 6-3

[0137] (Solid nuclides in chloride tank 1) The chlorides (60 nuclides in the example) generated in the soluble substance tank and the gas tank existing in chloride tank 1 are put into the vaporization tank, heated in ascending order of the boiling point of chloride, vaporized in the rectification column for each boiling point, and fractionated as chloride gas by the condenser. The stable nuclides or stable isotopes are recovered into the nuclide recovery tank through the cooling device, and the radioactive nuclides or radioactive isotopes and the isotopes mixed with radioactive and stable nuclides are recovered into the vitrified nuclide recovery tank. Furthermore, for the two types of isotopes of radioactive and stable nuclides that can be reused as resources, isotope separation is performed using a gas centrifuge device that utilizes the mass difference used in uranium fuel production, separating them into light nuclides that are stable and have a small mass number and heavy nuclides that are radioactive and have a large mass number, and recovering them into the light nuclide recovery tank and the heavy nuclide recovery tank respectively. Since it would be redundant to describe the recovery process in ascending order of the boiling point, it is described for each recovery method.

[0138] (Recovery of stable nuclides in chloride tank 1, including the solid tank attached to the gas tank) Heat the chloride bath 1 to 87 °C to obtain germanium chloride (stable isotope 32Ge70 / 72; 76.7 mg), heat it to 196 °C to obtain selenium chloride (34Se82; 22.7 g), heat it to 331 °C to obtain zirconium chloride (stable isotope 40Zr90 - 92; 62.8 kg), heat it to 432 °C to obtain hafnium chloride (stable isotope Hf177 - 178; 561.7 kg), heat it to 623 °C to obtain tin chloride (radioactive nuclide 50Sn117m; 3.4E - 37 g can be ignored, stable nuclide Sn117; 9.75 kg), heat it to 1388 °C to obtain rubidium chloride (37Rb85 in the gas bath; 623 g), heat it to 1453 °C to obtain ytterbium chloride (stable isotope 70Yb172 / 173; 172.4 kg), heat it to 1500 °C to obtain holmium chloride (67Ho165; 14.5 kg) and erbium chloride (68Er167; 108.3 kg), heat it to 1530 °C to obtain dysprosium chloride (66Dy161 / 162; 77.1 kg), heat it to 1580 °C to obtain gadolinium chloride (64Gd154 / 155 / 158; 26.9 kg), vaporize and fractionate them, and recover them in the nuclide recovery tank through the cooling device. If the recovery tanks are made individual, chlorides of these stable nuclides can be recovered. In the chloride bath 1, the weights of gallium with a chloride boiling point of 201 °C, palladium with a boiling point of 675 °C, zinc with a boiling point of 732 °C, barium with a boiling point of 1560 °C, and promethium with a boiling point above 1600 °C are all 1 μg or less, and recovery is difficult. Note that erbium chloride and holmium chloride, both with a boiling point of 1500 °C as mentioned above, can be separated by the difference in their melting points.

[0139] (Recovery of vitrified nuclides in the chloride bath 1) Heat the chloride bath 1 to 632 °C to obtain europium chloride (radioactive isotope 63Eu154 / 155; 2.5 g and stable nuclide Eu151; 21 μ g are mixed), heat it to 682 °C to obtain samarium chloride (radioactive nuclide 62Sm151; 0.5m g and stable isotopes Sm152 / 154; 0.3 μ g are mixed), heat it to 960 °C to obtain cadmium chloride (radioactive nuclide 46Cd116; 16.2g) is heated to 1480 °C to vaporize and fractionate lutetium chloride (radioisotope 71Lu177m / 177; 119 g), and heated to 1507 °C to vaporize and fractionate yttrium chloride (radioisotope 39Y90 / 91; 6.1 g), and then recovered in the vitrified nuclide recovery tank through a cooling device. Neodymium chloride with a boiling point of 1600 °C or higher, which is a radionuclide; 0.73 pg and cerium chloride; 2.8p g is in trace amounts and the radioactivity is 0.03 fBq and 5.2 fBq respectively negligible. The radioactivity of the radionuclide Cd116 is 55.8 μBq, and the probability of existence on Earth is 7.5%. It is considered that there is no need for vitrification. In addition, lutetium chloride can be used in radioactive pharmaceuticals, so it is recovered.

[0140] (Nuclides that can separate stable nuclides and radionuclides in chloride tank 1 for resource recovery) Chloride tank 1 is heated to 1250 °C to vaporize and fractionate strontium chloride (mixed with radionuclide 38Sr90; 23.9 kg and stable nuclide Sr88; 32.7 kg), then fractionated through a cooling device, and nuclide separation is performed with a gas centrifuge device using the mass difference, separating into stable nuclides with a small mass number and radioactive nuclides with a large mass number. The stable nuclides can be recovered in the light nuclide recovery tank, and the radioactive nuclides can be recovered in the heavy nuclide recovery tank.

[0141] (Solid nuclides existing in chloride tank 2) Next, the chlorides existing in chloride tank 2 (in the example, 35 nuclides) are put into the vaporization tank, heated in ascending order of the boiling points of the chlorides in the same manner as above, and the chlorides vaporized in the rectifying column for each boiling point are taken out as chloride gas with a condenser. If they are stable nuclides or stable isotopes, they are recovered in the nuclide recovery tank through a cooling device. Radionuclides or radioisotopes and isotopes mixed with stable nuclides are recovered in the vitrified nuclide recovery tank. Since the nuclides generated in the soluble substance tank and the nuclides generated in the insoluble substance tank are treated separately, the weight of the waste nuclides to be vitrified can be reduced.

[0142] (Recovery of stable nuclides in chloride bath 2) Heat chloride bath 2 to 131 °C to vaporize arsenic chloride (33As75; 5.5 g), heat it to 196 °C to vaporize selenium chloride (34Se77; 32.4 g), heat it to 268 °C to vaporize molybdenum chloride (stable isotopes 42Mo97 / 98; 5.26 kg), heat it to 500 °C to vaporize ruthenium chloride (stable nuclide 44Ru101; 6.39 kg), heat it to 960 °C to vaporize cadmium chloride (stable isotopes 48Cd111 / 114; 2.38 kg), and heat it to 1550 °C to vaporize silver chloride (stable isotopes 47Ag107 / 109; 712.5 kg). Then, separate them by distillation and recover them in the nuclide recovery tank through a cooling device. Since ruthenium chloride decomposes thermally at its boiling point, it can be recovered as a metal. Note that boron chloride with a boiling point of 12.6 °C and gallium chloride with a boiling point of 201 °C are present in trace amounts of 1 μg or less and are difficult to recover.

[0143] (Recovery of vitrified nuclides in chloride bath 2) In chloride bath 2, heat tellurium chloride (a mixture of radioactive isotopes 52Te125m / 127m / 127 / 128; 58.3 g and stable isotopes Te122 / 124 / 125 / 126; 3.15 kg) to 380 °C, heat beryllium chloride (a mixture of radioactive nuclide 4Be10; 9.8 mg and stable nuclide Be9; 6 μg) to 547 °C, heat tin chloride (a mixture of radioactive nuclide 50Sn126; 4.9 mg and stable isotopes Sn114 / 116 / 122; 71 pg) to 623 °C, heat palladium chloride (radioactive nuclide 46Pd107; 7.76 kg) to 675 °C, then vaporize and fractionate them, and recover them in the vitrified nuclide recovery tank through a cooling device. Note that antimony chloride at 224 °C (a mixture of radioactive isotopes 51Sb124~126 / 126m; 0.25 ng and stable isotope Sb123; 0.7 ng) cannot be recovered in trace amounts. Zirconium with a sublimation point of 331 °C contains a mixture of radioactive nuclide 40Zr96 (natural abundance 2.8%; 23.5 kg) and stable isotopes Zr90 / 94 (931 g), and its radioactivity is 82.9 mBq, which can be treated as radioactive waste without vitrification. Also, as will be described later, since the σp of 46Pd107 is large even for thermal neutrons, it can be converted into Pd109m (IT, 4.7 m) by thermal neutron irradiation and recovered as stable 47Ag109.

[0144] (Gas nuclides generated in the gas tank, soluble substance tank, and insoluble substance tank) 180 days after fuel removal, the generated gas nuclides are listed in Table 7 according to the boiling point order of the elements, including nuclide, decay mode, half-life, boiling point of the element, σp (value at thermal neutron energy of 0.0253 eV), weight after 6 years of no countermeasure, weight per tank, total weight of each tank [unit: g], radioactivity after 6 years of no countermeasure and after countermeasure [unit: Bq], and the time to reach 0.1 Bq after countermeasure and without countermeasure. Note that since carbon exists as an oxide, the boiling point of CO 2 was used as the boiling point.

[0145]

Table 7

[0146] The weights and volumes of gas nuclides 180 days after spent nuclear fuel removal (values at 1 atm / 20 °C are shown in [ ]) are 158.1 kg [27.3 m 3 for radioactive nuclides and 227.3 kg [43.5 m 3 for stable nuclides. After 6 years of being left unattended, due to countermeasures, the gas of radioactive nuclides decreased from 157.5 kg [27.1 m 3 to 146.0 kg [26.0 m 3 , and the stable nuclides increased from 227.3 kg [43.5 m 3 to 246.2 kg 48.8 m 3 . The weight [volume] of radioactive nuclide 54X e136 was 144.5 kg [25.6 m 3 after 6 years of no countermeasure, accounting for 91.7% [volume ratio 94.5%] of all radioactive nuclides. After countermeasures, the weight is the same but it accounts for 99.0% [same 98.5%] of radioactive nuclides. The weight of the second most abundant I129 is 11.5 kg [1.1 m 3 , accounting for 7.3% [same 4.1%], but it becomes 0% after countermeasures. In this embodiment, 3.0 kg of stable bromine (including 35Br79 / 81 generated in the soluble substance tank) and 1.4 kg of iodine (including 53I127 generated in the insoluble substance tank) generated can be recovered as a liquid and a solid respectively at room temperature. 11.5 kg of long-lived radioactive iodine (53I129) can be nuclide-converted into stable xenon (54Xe130). If the gas tank is cooled from room temperature in descending order of boiling point, the gas elements can be separated, but since radioactive gases and stable gases are mixed, isotope separation is difficult, and there are also problems with the recovery cost due to the use of cooling energy. Gas nuclides with a boiling point below room temperature will be discarded as before. The time to reach 0.1 Bq for the 5 nuclides 1H3, 6C14, 36Kr81 / 85, 54Xe136 with long half-lives has no countermeasure effect. However, for 53I129, the time to reach 0.1 Bq can be shortened from 620 million years to 180 days. The stable gaseous nuclides have increased by 7 types recovered from the soluble and insoluble tanks due to the countermeasures. For non-described radioactive gases, the time to reach 0.1 Bq becomes longer due to countermeasures There are 2 types. For 53I130 (β, 12.4 h), 30 days becomes 247.4 days, and for 53I130m (IT / β, 8.84 m), 8.4 hours becomes 217.5 days. This is due to the addition of the weight recovered from the soluble tank. . There are 2 types that are shortened by the countermeasures. For 53I131 (β, 8.03 d), it changes from 1.4 years to 180 days, and for 53I132 (β, 2.3 h), it changes from 207.8 days to 184.6 days. This is due to irradiating iodine with thermal neutrons only once. . Twelve types with a short half-life of 35Br80 (β / ec, 17.7 m) / Br80m (IT, 4.42 h) / Br82m (IT / β, 6.1 m) / Br82 (β, 35.3 h), 36Kr79 (ε, 35 h) / Kr81m (IT / β, 13 s) / Kr85m (β / IT, 4.5 h), 53I128 (β / ec, 25 m) / I134 (β, 52.5 m), 54Xe135 (β, 9.1 h) / Xe135m (IT, 15.3 m) / Xe137 (β, 3.8 m) will have a nuclide weight of 0 g and a radioactivity of 0 Bq 180 days after the spent fuel is removed. The remaining seven nuclides, 35Br83 (β, 2.4 h), Kr83m (IT, 1.8 h), I133 (β, 20.8 h), 54Xe129m (IT, 8.88 d) / Xe131m (IT, 11.8 d) / Xe133 (β, 5.25 d) / Xe133m (IT, 2.19 d), are generated in the soluble material tank and the recovered weight is added. Although there is no effect of the countermeasure, the time to reach 0.1 Bq is less than two years.

[0147] The weights and radioactivities of the high-level radioactive solid nuclides generated in the soluble material tank, insoluble material tank, and gas tank after the countermeasures by neutron irradiation shown in Tables 6.1 to 6.3, as well as the weights of the stable solid nuclides, were calculated. For the nuclides generated in each tank, taking them as chlorides, elemental separation was performed according to their boiling points. For stable nuclides or isotopes, they were recovered. Also, reusable radioactive nuclides were recovered. In the case of radioactive nuclides or isotopes, and in the case where radioactive nuclides or isotopes are mixed with stable nuclides or isotopes, if the total radioactivity is 0.1 Bq or less, they are treated as radioactive waste. If it is 0.1 Bq or more, they are contained in a canister (internal volume 150 L, allowable weight 550 kg or less), made into a vitrified solid, and then treated. The weights and radioactivities of the stable solids, radioactive solids, solids to be discarded, and solids to be discarded after vitrification that can be recovered by the countermeasures were evaluated by the recovery rate and the waste glass solidification rate, and the results are shown in Table 8.1. Note that this weight is the value of the nuclide alone, not the value of the chloride.

[0148]

Table 8-1

[0149] The FP 180 days after spent nuclear fuel removal is 1861 kg of solid nuclides (stable nuclides; 1228 kg, radioactive nuclides; 633 kg) and 385.4 kg of gaseous nuclides (stable nuclides; 227.3 kg, radioactive nuclides; 158.1 kg). If left untreated for 6 years, the solid nuclides will be 1861 kg (stable nuclides; 1254 kg, radioactive nuclides; 607 kg) and the gaseous nuclides will be 384.8 kg (stable nuclides; 227.3 kg, radioactive nuclides; 157.5 kg). However, by implementing the present invention, after 6 years, the solid nuclides will be 1853.8 kg (stable nuclides; 1798.5 kg, radioactive nuclides; 55.3 kg), and the gaseous nuclides will be 392.3 kg (stable nuclides; 246.3 kg, radioactive nuclides; 146.0 kg). The solid weight will decrease by 99.6%, and the gaseous weight will increase by 102%. The stable nuclides of the solid will increase by 143.4 %, and the radioactive nuclides will decrease by 9.1 %. The stable nuclides of the gas will be 108.4increased by %, and the radionuclide is 92.7 decreased by %. After leaving the spent nuclear fuel unaddressed for 6 years When elemental separation is performed on the described 1052 kg of 86 nuclides using the difference in boiling points, the weight of the vitrified nuclides to be discarded (excluding the non-described weight) is approximately the same and the vitrification rate is approximately 100% However, due to the countermeasures, out of the total weight of 1854 kg of the individual solid nuclides existing in the soluble material tank (including the gas tank) and the insoluble material tank, which are 1092 kg and 762 kg respectively, the individual weights of the nuclides to be vitrified are 8.6 g and a total of 10.97 kg 10.99 kg, and the weight to be discarded as vitrified waste can be reduced to 0.59 %. When converted to chlorides, the weights of the solids existing in the soluble material tank (including the gas tank) and the insoluble material tank are 1922 kg and 1027 kg, respectively increasing by 76.0% and 34.8%. The chlorides of the waste nuclides to be vitrified weight is 14.6 g and 19.7 kg, respectively increasing by 1.7 times and 1.8 times. However, even when added together, it is 20 kg or less and it is within 1 canister to be discarded as a vitrified waste. In addition, the radioactivity of 46Cd116 (2β, 3.3E+19y), a cadmium radionuclide generated in the soluble material tank 16.2 g is 55.8 μ Bq, and the natural abundance is 7.49%. It is not included in the waste vitrified body but is included in the waste treatment solid. Similarly, for zirconium generated in the insoluble material tank (radioactive nuclide 40Zr96; 23.5 kg and stable isotopes 40Zr90 / 94; 0.9 kg are mixed present) 24.4 kg, the radioactivity of the radioactive nuclide Zr96 (2β, 3.9E+19y) is 82.9 mBq, and the natural abundance is 2.80%. Therefore, it is not included in the waste vitrified body but is included in the waste treatment solid. The radioactivity of the waste radioactive gas nuclides after leaving the FP generated from the spent nuclear fuel unaddressed for 6 years is 22.1 PBq, and there is no increase or decrease due to the countermeasures. However, the radioactivity of 957.3 PBq of the radioactive solid nuclides becomes It decreases to 269 PBq, the radioactivity of the recycled radionuclides is 146.5 PBq, and the radioactivity of the radionuclides to be vitrified for disposal is 122.5 PBq due to the countermeasures. The radioactive waste to be treated is the radioactivity of 83 mBq of 24.4 kg of zirconium (radioactive nuclide 40Zr96; 23.5 kg and stable isotopes Zr90 / 94; 931 g are mixed) and the radioactivity of the cadmium radionuclide (46Cd116) 16.2 g55.8 It will only be in μBq.

[0150] (Nuclides recoverable for reuse in the soluble material tank and gas tank and nuclides for vitrification) The stable chlorides of soluble nuclides recoverable in the soluble material tank and their weights (nuclides alone) are 22.7 g of selenium (34Se82), 623.3 g of rubidium (gas tank 37Rb85), 32.7 kg of strontium (38Sr88), and 26.9 kg of gadolinium (64Gd154 / 155 / 158), 77.1 kg of dysprosium (66Dy161 / 162), 14.5 kg of holmium (67Ho165), 108.3 kg of erbium (68Er167), 172.4 kg of ytterbium (70Yb172 / 173). The stable chlorides of insoluble nuclides and their weights (nuclides alone) are 76.7 mg of germanium (32Ge70 / 72 / 73), 62.8 kg of zirconium (40Zr90 / 91 / 92), 9.75 kg of tin (50Sn117), 561.6 kg of hafnium (72Hf177 / 178). In the soluble material tank (including the gas tank), the total is 1068 kg, and these chlorides can be reduced and reused as metals. The recoverable radionuclides and their weights (nuclides alone) are 23.9 kg of strontium (38Sr90) and 118.6 g of lutetium (71Lu177m / 177), with a total of 24.0 kg. 38Sr90 (β, 28.8y) can be used in the atomic power battery for the power source of unmanned machinery, and 71Lu177 (β, 6.65d) can be used in the radionuclide therapy for neuroendocrine tumors and is used in the radiopharmaceutical "Generic Name: Lutetium Oxodotretotide (177Lu)". (Source: The Japanese Society of Nuclear Medicine) The nuclides for vitrification and their weights are 6.08 g of yttrium (radioisotope 39Y90 / 91), 0.3 μg of samarium (radionuclide 62Sm151; 0.5 mg and stable isotope 62Sm152 / 154; 0 / 3 μg), and 2.5 g of europium (radioisotope 63Eu154 / 155; 2.5 g and stable nuclide Eu151; 20.5 μg), with a total of 8.6 g. The amount of cadmium (48Cd116) with a radioactivity of 55.8 μBq that is discarded as non - vitrified radioactive waste is 16.2 g.

[0151] (Isotopes recoverable for reuse in the insoluble material tank and nuclides to be made into glass solidified bodies) The chlorides of soluble stable nuclides that can be recovered in the insoluble material tank and their weights (nuclide alone) are: arsenic (33As75) is 5.5 g, selenium (34Se77) is 32.4 g, silver (47Ag107 / 109) is 712.5 kg, cadmium (48Cd111 / 114) is 2.38 kg. The insoluble stable chlorides and their weights (nuclide alone) are: molybdenum (42Mo97 / 98) is 5.26 kg, ruthenium (44Ru101) is 6.39 kg. The total is 726.6 kg. These chlorides can be reduced and reused as metals. There are no radioactive nuclides that can be recovered. The nuclides to be made into glass solidified bodies and their weights (nuclide alone) are: palladium (radioactive nuclide 46Pd107) is 7.76 kg, tin (radioactive nuclides 50Sn126; 4.9 mg and stable isotopes Sn114 / 116 / 122 / 124; 71 pg) is 4.9 mg, antimony (radioactive isotopes 51Sb124 / 125 / 126m / 126; 0.25 ng and stable nuclide Sb123; 0.7 ng) is 0.95 ng, tellurium (radioactive isotopes 52Te125m / 127 / 127m / 128; 58.3 g and stable isotopes 52Te122 / 124 / 125 / 126; 3.15 kg) is 3.21 kg. The total is 10.97 kg. Also, as described above, the amount of zirconium (48Cd116) with a radioactivity of 83 mBq that is discarded as non - vitrified radioactive waste is 24.4 kg. Note that since the σp of 46Pd107 to be made into a glass solidified body is as large as 9.9 for thermal neutrons (0.0253 eV), if it is nuclide - converted to 46Pd109m by thermal neutron irradiation, it decays as Pd109m(IT, 3.1 s)→Pd109(β, 13.6 h)→47Ag109m(IT, 39.8 s)→Ag109(stable). After 41.2 days of irradiation, the radioactivity of the radioactive nuclide becomes 0.1 Bq or less and is recovered as 7.76 kg of stable 47Ag109. The stable solid recovery rate after the countermeasure is96.7 from 97.2 % to 0.59 %, the vitrification ratio of waste glass improves from

[0152] Approximately 1.25 pieces of vitrified products (high-level radioactive waste) are produced from 1 t of spent nuclear fuel. (China Power homepage: https: / / www.enerugia.co.jp) Generally, when the concentration of uranium-235 is 3.7% (5%) in a nuclear power generation of 1 million kW, approximately 31.5 t (22.6 t) of spent nuclear fuel is produced annually, and from this, approximately 15.8 m 3 (11.3 m 3 ) of high-level radioactive waste liquid is generated, and it is said that approximately 32 pieces (23 pieces) of vitrified products are produced. (Japan Atomic Energy Agency, Encyclopedia of Nuclear Power ATOMICA) The nuclear fuel of Unit 2 of the Fukushima Daiichi Nuclear Power Plant (electric output: 784,000 kW) has a U-235 concentration of 3.7%. Since the nuclear fuel required for power generation in one year is 24.4 t, the number of vitrified products is 31 pieces from the former and 25 pieces from the latter when calculating the vitrified products. 180 days after the removal of nuclear fuel, the weight of a single solid nuclide in FP is 1.86 t ( When the weight of the chloride of the solid nuclide is calculated, it is 1.62 times the weight of the single nuclide. When converted to the weight of the chloride, it becomes 3.0 t . By implementing the present invention, the weight of a single nuclide to be made into a vitrified product can be 11.0 kg (in terms of chloride conversion 17.8 kg) and reduced. The number of canisters for vitrified products is 0.29 pieces in the former calculation and 0.24 pieces in the latter calculation. Furthermore, considering the case where the spent nuclear fuel is left untouched for several years or more after removal, when the method of the present invention is applied to the nuclides 10 years after the removal of nuclear fuel and processed in the same way, that is, when it is left untouched for 16 years after the removal of nuclear fuel, the calculated results 16 years after the countermeasures are shown in Table 8.2.

[0153]

Table 8-2

[0154] Comparing the situation after leaving it unaddressed for 16 years with that after 6 years regarding the nuclide weight, in the case of solids, for radionuclides 96.3 %, and for stable nuclides 101.9 %, showing that the decay from radionuclides to stable nuclides progresses. In the case of gases, the radionuclides decrease to 99.6%, while the stable nuclides do not change, remaining at 100%. It is considered that the gaseous radionuclides decay into solids instead of decaying into stable gases. Due to the countermeasures, the weight of the stable solid recovered from the spent nuclear fuel after being left unaddressed for 10 years is 1815 kg, showing little change. The weight of the recovered radioactive solid is 20.96 kg, showing a decrease of about 13%. The weight of the waste glass solidified body is 10.97 kg and 17 g, showing little change with only a decrease. The weight of the waste treatment solid is 28.28 kg, showing an increase of 15.8%. Even when the spent nuclear fuel is left unaddressed for 10 years, the waste glass solidification rate is approximately the same as the value after the countermeasures 180 days after the removal of the spent nuclear fuel, indicating that the effect of the present invention is considered to be present.

[0155] 〔References〕and 〔Data Citation Sources〕 〔Reference 1〕Tsutomu Sakurai, Akira Takahashi, "Behavior of Iodine during Reprocessing", JAERI-Review 97-002, Japan Atomic Energy Research Institute, https: / / doi.org / 10.11484 / jaeri-review-97-002 〔Reference 2〕Japanese Patent Application Laid-Open No. 05-072390, Method for Treating 14CO2, Industrial Technology Creation Institute 〔Reference 3〕Hiroaki Tagawa, "Thermal Decomposition of Nitrates", Yokohama National University Environmental Research Institute Bulletin 14: p.41-57 (1987) https: / / ynu.repo.nii.ac.jp / 〔Reference 4〕Kensuke Kinoshita, Masateru Kurata, "Separation Technology of Transuranium Elements from High-Level Waste Liquor", Electric Power Central Research Institute Review No.37, p49-58 https: / / criepi.denken.or.jp / koho / review / No37 / chap-6.pdf [Data source 1] IAEA Nuclear Structure and Decay Data; IAEA Nuclear Data Section, Vienna International Centre, PO Box 100 A-1400 Vienna, Austria https: / / www-nds.iaea.org / relnsd / vcharthtml / VChartHTML.html [Data source 2] Japan Atomic Energy Agency, Nuclear Data Research Group, JENDL-5 https: / / wwwndc.jaea.go.jp / jendl [Data source 3] Kenji Nishihara, Daisuki Iwamoto, Kinya Suga, "Evaluation of Fuel Composition of Fukushima Daiichi Nuclear Power Station Unit 2", JAEA-Data / Code 2012-018, Japan Atomic Energy Agency https: / / jopss.jaea.go.jp / pdfdata / JAEA-Data-Code-2012-018.pdf [Industrial Applicability]

[0156] In this example, the weight of the nuclides to be vitrified among the solid nuclides of FP 180 days and 10 years after the removal of the spent nuclear fuel of Unit 2 of the Fukushima Daiichi Nuclear Power Station of Tokyo Electric Power Company was calculated. If the weight of FP generated from the spent nuclear fuel generated at other nuclear power plants is given, the worksheet of this example can be applied to obtain the weight of the nuclides to be vitrified. Furthermore, by implementing the present invention, the ratio of the vitrified body of high-level radioactive waste of spent nuclear fuel generated by nuclear power generation can be reduced to 1% or less, so the required area of the high-level radioactive waste storage facility is reduced, storage management becomes easier, the options for waste storage locations are expanded, and furthermore, it serves as a foundation for increasing the ratio of nuclear power generation in the supplied electricity, and it is considered that it can contribute to the suppression of global warming. [Explanation of Reference Signs]

[0157] 1 Gas tank 2 Solid tank 3 Soluble substance tank 4 Insoluble substance tank A 5 Insoluble matter tank 6 Soluble matter tank B 7 Thermal neutron source device 8 Cold neutron source device 9 Neutron irradiation shutter 10 Solid-liquid separation device 11 Filtration device 12 Liquid iodine tray 13 Cooling device 14 Iodide tank 15 Chloride tank 1 (with solidification device) 16 Chloride tank 2 (with solidification device) 17 Vaporization device 18 Rectification column 19 Condenser 20 Heating device 21 Nitric acid solution inlet 22 Hydrochloric acid solution inlet 23 Chlorine gas inlet 24 Valve (for liquid) 25 Valve with backflow prevention (for liquid) 26 Valve with backflow prevention (for gas) 27 Vacuum pump 28 Liquid reflux pump 29 Radiation dose monitor 30 Gas release valve 31 Flow path switching valve 32 Heating device with temperature control 33 Nitric acid recovery device 34 Cooling device 35 Stable nuclide recovery tank 36 Glass solidified nuclide recovery tank 37 Liquefied iodine extraction pipe 38 Gas centrifuge device 39 Heavy nuclide recovery tank 40 Light nuclide recovery tank

Claims

1. Among the fission products generated from spent nuclear fuel, a gas tank for recovering gaseous nuclides generated immediately after fuel removal, and a process for recovering uranium, plutonium, and actinides from spent nuclear fuel, and storing the remaining fission products in a soluble material tank for a predetermined period of time, and then storing the nuclides soluble in nitric acid. The nuclides soluble in nitric acid in the soluble material tank are irradiated with thermal neutrons for the first time. After storage for a specified time, immediately before the second thermal neutron irradiation, the gaseous nuclides generated by radioactive decay in the soluble material tank are recovered into the gas tank, and the nuclides sparingly soluble or insoluble in the resulting nitric acid (hereinafter referred to as sparingly soluble nuclides) are separated and recovered into another storage tank. The gases and sparingly soluble solid nuclides generated by decay are not irradiated with thermal neutrons, and the filtered nitric acid and the nuclides soluble in nitric acid are refluxed to the soluble material tank. The nuclides in the soluble material tank are irradiated with thermal neutrons for the second time and stored for a specified time. Thereafter, only the nuclides soluble in nitric acid stored in the soluble material tank are repeatedly irradiated with thermal neutrons and stored for a specified time multiple times. During the storage period after thermal neutron irradiation in the soluble material tank, the gaseous nuclides generated by radioactive decay are recovered into the gas tank, and the generated sparingly soluble nuclides are recovered into another storage tank. The gaseous nuclides and the sparingly soluble nuclides are not irradiated with thermal neutrons. A method for treating radioactive waste, characterized in that.

2. The gas tank described in claim 1, and a process for recovering uranium, plutonium, and actinides from spent nuclear fuel, and separating and storing the nuclides sparingly soluble or insoluble in nitric acid from the remaining fission products after a predetermined period of time in a sparingly soluble material tank. After irradiating the sparingly soluble nuclides in the sparingly soluble material tank with thermal neutrons for the first time, a nitric acid solution of a specified concentration is introduced into the sparingly soluble material tank. After storage for a specified time, the gaseous nuclides generated by radioactive decay are recovered into the gas tank, and the nuclides soluble in the resulting nitric acid are filtered together with the nitric acid solution and recovered into another storage tank. Immediately after irradiating the nuclides in the sparingly soluble material tank with thermal neutrons for the second time, the nitric acid solution filtered and recovered into another storage tank is refluxed to the sparingly soluble material tank and stored for a specified time. The gaseous nuclides generated by decay are recovered into the gas tank, and the nuclides soluble in nitric acid are filtered together with the nitric acid solution and recovered into another storage tank. Thereafter, a nitric acid solution containing nuclides soluble in nitric acid recovered immediately after irradiating the sparingly soluble nuclides in the sparingly soluble material tank with thermal neutrons (after a specified time from the previous thermal neutron irradiation) is refluxed to the sparingly soluble material tank, and storage for a specified time is repeated multiple times. During the storage period after thermal neutron irradiation, the gaseous nuclides generated by radioactive decay are recovered into the gas tank, and the solid nuclides soluble in nitric acid are recovered into another storage tank. The gases and soluble nuclides are not irradiated with thermal neutrons. A method for treating radioactive waste, characterized in that.

3. The gas tank described in Claim 1 is equipped with a device for recovering the gaseous nuclides generated in the soluble substance tank described in Claim 1 and the gaseous nuclides generated in the sparingly soluble substance tank described in Claim 2 into the gas tank. A nitric acid solution of a specified concentration is added to the gas tank to store the solid nuclides generated by the decay of the gaseous nuclides in the gas tank in a solid tank. It is equipped with an iodide tank that vaporizes or sublimates iodine and bromine in the gas tank, liquefies only iodine, separates it, and recovers it. After a specified time has elapsed since the spent nuclear fuel was removed, just before the first cold neutron irradiation, it is combined with the gas recovered from the soluble substance tank and the sparingly soluble substance tank, and only the iodine present in the gas tank is liquefied, separated, and recovered in the iodide tank. Only the separated iodine is irradiated with thermal neutrons once. After that, including the gas recovered from the soluble substance tank and the sparingly soluble substance tank, the solid nuclides generated by the decay of the radioactive gaseous nuclides in the gas tank are recovered in another storage tank, and the gaseous nuclides and the solid nuclides generated in the gas tank are not irradiated with neutrons. A method for treating radioactive waste, characterized by this.

4. After all the treatments of the radioactive waste described in Claims 1 to 3 are carried out and left for a specified time, the total solid nuclides generated in the gas tank described in the treatment method of Claim 3 are added to the total solid nuclides of the soluble substance tank generated by the treatment method of Claim 1, and the total solid nuclides of the sparingly soluble substance tank generated by carrying out the treatment of the radioactive waste described in Claim 2 are separately denitrified and then converted into chlorides. Element separation is carried out by a fractional distillation method using the difference in the boiling points of the chlorides. After separately denitrifying, converting into chlorides, and carrying out element separation by a fractional distillation method using the difference in the boiling points of the chlorides, if necessary, isotope separation is carried out using the gas centrifuge method, useful radioactive nuclides and stable nuclides that can be reused as resources are recovered, and the amount of waste of the nuclides to be vitrified is minimized. A method for treating radioactive waste, characterized by this.

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