Radiation decomposition device and radiation decomposition method

Abstract

Provided is a radiation decomposition device and a radiation decomposition method that allow efficient decomposition of an irradiated substance while reducing the size of equipment as much as possible. A radiation decomposition device (100) according to the present invention is characterized by including: a radiation source (101) that emits radiation released from a sealed radioactive substance; a reaction tank (103) that contains a to-be-irradiated substance (104); and a heat transfer tank (102) that covers the radiation source (101) and transfers, to the reaction tank (103), heat generated by the decay of the radioactive substance. It is preferable that the radiation source (101) is: a radiation source formed of spent nuclear fuel or vitrified waste containing fission products extracted from spent nuclear fuel; a radiation source containing fission products extracted from spent nuclear fuel; a radiation source containing Co-60; a radiation source containing Cs-137; or a high-level radioactive waste liquid.

Description

Radiolysis apparatus and radiolysis method

[0001] The present invention relates to a radiolysis apparatus and a radiolysis method.

[0002] The energy of radiation emitted by the decay of radioactive isotopes and nuclear reactions, as well as the energy of electrons and charged particles accelerated by accelerators, are utilized in many industries. For example, nuclear power generation uses the energy produced by nuclear reactions using nuclear fuels such as uranium to generate electricity. In radiation cancer treatment, protons, carbon, X-rays, and gamma rays accelerated by accelerators are irradiated onto cancerous tissue, and the energy is used to break down the cancerous tissue. In radiological diagnosis, examples include X-ray diagnostics, X-ray computed tomography (CT), and positron emission tomography (PET). In the industrial field, examples include non-destructive testing using X-rays, manufacturing of semiconductor devices and analysis of irradiated materials using electron beams, improvement of radial tire properties by electron beam irradiation, and sterilization of medical equipment by electron beam and gamma ray irradiation. Furthermore, in the fields of agriculture, environment, and resources, examples include food irradiation of potatoes, spices, meats, and onions, pest control such as sterilization of melon flies, and improvement of rice varieties.

[0003] As demonstrated in radiation cancer treatment, improvement of radial tire properties, and sterilization of medical equipment, the energy of radiation can be used to alter the state of matter. This is due to the breaking of bonds between elements and molecules, which can lead to the decomposition and polymerization of materials, as well as the creation of new materials through the recombination of decomposed substances.

[0004] Radiolysis equipment is required not only to decompose cancer cells and fungi, but also to decompose biomass waste to produce biomass fuels such as bioethanol and biomethanol, biomass gas, and biomass plastics, as well as methane and hydrogen from these biomass materials, and to decompose harmful substances such as dioxins and perfluorooctanesulfonic acid compounds (PFAS). Furthermore, radiolysis equipment is required to improve economic efficiency by minimizing the amount of equipment used while improving the radiolysis efficiency. Methods and equipment for decomposing these irradiated targets by radiolysis are being developed in various places.

[0005] For example, Patent Document 1 describes inventions relating to carbohydrate-containing materials (e.g., biomass materials or biomass-derived materials), methods for producing such materials, methods for processing such materials to change their structure, and products produced from structurally altered materials. Patent Document 1 describes, as an example of its invention, a method for producing an acid, which is described below. Specifically, the method includes the steps of contacting a pre-treated biomass raw material with microorganisms or enzymes to saccharify the pre-treated biomass raw material and release sugar, and fermenting the sugar into a polyfunctional organic acid. In this method, the raw material is pre-treated by irradiating it with an electron beam for a time sufficient to deliver radiation irradiation of 100 kGy to 1500 kGy at a dose rate of at least 10 kGy / second to the biomass raw material. The biomass raw material also includes cellulose material or lignocellulose material.

[0006] Furthermore, for example, Patent Document 2 describes a waste storage facility that can perform a low-cost and practical detoxification treatment by utilizing the gamma rays emitted by the waste in a high-dose waste storage facility to decompose harmful chlorine-based organic substances contained in the waste. This invention is characterized by providing a facility in which, at least a portion of the area around the high-level radioactive waste liquid storage tank is equipped with a retention means configured to receive irradiation from gamma rays emitted from the surface of the storage tank for a certain period of time while the material to be treated enters from one side and exits from the other, and means for supplying and removing the material to be treated is also provided.

[0007] Japanese Patent Publication No. 2019-150824 Japanese Patent Publication No. 2001-91695

[0008] In radiolysis apparatuses, there is a desire to efficiently decompose irradiated materials while keeping the equipment size as small as possible. The invention described in Patent Document 1 improves the efficiency of biomass pretreatment by incorporating a process of pretreatment of biomass raw materials by one or more means such as radiation irradiation, sonic treatment, oxidation, thermal decomposition, or steam explosion. In other words, in the invention described in Patent Document 1, it is necessary to configure the apparatus using multiple methods in order to increase efficiency, which requires the construction of large-scale equipment and the complex operation of such equipment. Furthermore, in the invention described in Patent Document 1, it is not simply a matter of increasing the amount of equipment, but rather an apparatus configuration and method for efficiently decomposing irradiated materials is required.

[0009] The invention described in Patent Document 2 utilizes radiation emitted from high-dose radioactive waste to decompose chlorine-based hazardous substances, enabling radioactive decomposition of irradiated materials without the need to construct large-scale facilities. Means for improving the efficiency of decomposition include adjusting the size of the radiation source and controlling the rate at which the irradiated material is fed. However, adjusting the size of the radiation source, i.e., the amount of radioactivity, is generally done during the radiation source manufacturing stage before it is introduced into the facility, making it difficult to adjust the amount of radioactivity during facility operation. Furthermore, Patent Document 2 illustrates a configuration in which the irradiated material is fed through a hose-like structure, but this configuration is difficult to apply to a wide variety of irradiated materials due to their dimensions, viscosity, and fluidity. Moreover, the hose-like shape limits the total amount of irradiation. Therefore, it is difficult to efficiently decompose the irradiated material.

[0010] This invention has been made in view of the above circumstances. The object of this invention is to provide a radiolysis apparatus and a radiolysis method that can efficiently decompose irradiated material while keeping the equipment size as small as possible.

[0011] The radiolysis apparatus according to the present invention, which solves the aforementioned problems, is characterized by comprising: a radiation source that irradiates with radiation emitted from a sealed radioactive material; a reaction vessel that encloses the material to be irradiated; and a heat transfer vessel that covers the radiation source and transfers the heat generated by the decay of the radioactive material to the reaction vessel.

[0012] According to the present invention, it is possible to provide a radiolysis apparatus and radiolysis method that can efficiently decompose irradiated material while minimizing the scale of the equipment. Problems, configurations, and effects other than those mentioned above will be clarified by the following description of embodiments. Further features related to the present invention will be evident from the description herein and the accompanying drawings.

[0013] This is a schematic cross-sectional view showing an example of the configuration of the radiolysis apparatus 100 according to the first embodiment. This is a cross-sectional view taken along line II-II in Figure 1. This is a cross-sectional view taken along line III-III in Figure 1. This is a cross-sectional view taken along line IV-IV in Figure 1. This is an enlarged view of section V in Figure 1. This is an enlarged view of section VI in Figure 1. This is a flowchart explaining the contents of the radiolysis method according to the first embodiment. This is a flowchart showing the work step (S100) of the radiolysis apparatus 100 described in the first embodiment. This is a flowchart showing the work step (S200) of the radiolysis apparatus 100 according to the second embodiment. This is a longitudinal cross-sectional view explaining an example of the configuration of the reaction vessel 103 of the radiolysis apparatus 100 according to the third embodiment. Effective atomic number Z of the Compton electron generating material 117 eff and Compton cross-sectional area ε eff This graph illustrates the relationship between the effective thickness t of the Compton electron-generating material 117. eff This graph illustrates the relationship between the probability of existence p of Compton electrons in a material. The effective thickness t of the Compton electron generating material 117. eff This is a graph illustrating the relationship between the amount of Compton electrons emitted and A. This is a longitudinal cross-sectional view illustrating another configuration example of the reaction vessel 103 of the radiolysis apparatus 100 according to the third embodiment. This is a longitudinal cross-sectional view illustrating another configuration example of the reaction vessel 103 of the radiolysis apparatus 100 according to the third embodiment. This is a longitudinal cross-sectional view illustrating another configuration example of the reaction vessel 103 of the radiolysis apparatus 100 according to the third embodiment. This is a schematic cross-sectional view showing an example configuration of the radiolysis apparatus 100 according to the fourth embodiment. This is a temperature monitoring diagram of the reaction vessel 103. This is a flowchart showing the work step (S300) of the radiolysis apparatus 100 according to the fourth embodiment. This is a schematic cross-sectional view showing an example configuration of the radiolysis apparatus 100 according to the fifth embodiment.

[0014] This invention relates to a technology for decomposing irradiated materials by radiation, and is based on new findings obtained through various studies to efficiently decompose irradiated materials with a minimal equipment configuration. Hereinafter, an embodiment of the radiolysis apparatus and radiolysis method will be described with reference to the drawings as appropriate. Note that common components in the following description and drawings may be denoted by the same reference numerals, and redundant explanations may be omitted. Furthermore, this invention is not limited to the following embodiments. Moreover, the description herein is merely a typical example and does not limit the claims or applications in any sense.

[0015] [First Embodiment] (Radiolysis Apparatus) A radiolysis apparatus 100 and a radiolysis method according to the first embodiment of the present invention will be described with reference to Figures 1 to 7. Figure 1 is a schematic cross-sectional view showing an example of the configuration of the radiolysis apparatus 100 according to the first embodiment. As shown in Figure 1, the radiolysis apparatus 100 according to the first embodiment comprises a radiation source 101, a heat transfer tank 102, and a reaction tank 103. The radiation source 101 irradiates with radiation emitted from a sealed radioactive material. The reaction tank 103 contains the material to be irradiated 104. The heat transfer tank 102 covers the radiation source 101 and transfers heat (decay heat) generated by the decay of the radioactive material to the reaction tank 103. The radiolysis apparatus 100 also comprises a radiation source storage device 105, a radiation source switching device 106, a radiation source control device 107, and a radiation controlled area 108. Operator 109 operates the radiation source 101 using a radiation source control device 107 which connects the radiation source storage device 105 and the radiation source switching device 106.

[0016] As the radiation source 101, for example, a radiation source formed from spent nuclear fuel used in a nuclear power plant or vitrified material containing fission products extracted from spent nuclear fuel, a radiation source containing fission products extracted from spent nuclear fuel, a radiation source containing Co-60, a radiation source containing Cs-137, or high-level radioactive waste liquid extracted from spent nuclear fuel can be used.

[0017] Spent nuclear fuel contains numerous radioactive materials produced by nuclear fission reactions and activation. While some radioactive materials have very short half-lives during or immediately after reactor operation, these materials decay during storage in the spent fuel pool within the nuclear power plant, leaving behind radioactive materials with a certain half-life within and around the spent nuclear fuel.

[0018] Typical radioactive materials remaining inside or around spent nuclear fuel include, for example, Mn-54, Fe-55, Co-60, Ni-63, Sr-90 / Y-90, Sn-119m, Sn-121, Sn-121m, Sn-125, Sn-126, Te-125m, U-235, U-237, U-238, U-240, Np-238, Np-239, Np-240m, Pu-238, Pu-239, Pu-240, Pu-241, Pu-242, Pu-243, Am-241, Am-242, Am-242m, Am- Examples include 243, Cm-242, Cm-243, Cm-244, H-3, Kr-85, Zr-93, Tc-99, Ru-106, Rh-102, Rh-106, Ag-109m, Ag-110, Ag-110m, Cd-113m, Sb-125, Sb-126, Sb-126m, Te-125m, Cs-134, Cs-137 / Ba-137m, Ce-144, Pr-144, Pr-144m, Pm-146, Pm-147, Sm-151, Eu-152, Eu-154, Eu-155, and Gd-153. These radioactive materials emit alpha rays, beta rays, gamma rays, neutron rays, and X-rays.

[0019] Outside the radiation source 101 is a heat transfer tank 102 that covers the radiation source 101. The heat transfer tank 102 is a common metal container made of a metal such as stainless steel, aluminum alloy, copper, or brass. The thickness of the heat transfer tank 102 shields alpha and beta rays, while gamma rays, bremsstrahlung radiation generated by the interaction between beta rays and the heat transfer tank 102, and X-rays pass through to the outside of the heat transfer tank 102. Alpha and beta rays impart their energy to at least the radiation source 101, of the two radiation sources 101 and the heat transfer tank 102. This energy is expressed as decay heat. The decay heat is transferred from the radiation source 101 to the irradiated material 104 via the heat transfer tank 102 and the reaction vessel 103. Note that both gamma rays and X-rays are electromagnetic waves (light), gamma rays are generated inside the atomic nucleus, and X-rays are generated outside the atomic nucleus. Bremsstrahlung radiation occurs when a fast-moving charged particle, such as an electron, passes near an atomic nucleus, is slowed down by the surrounding electric field, and the energy lost during this process is emitted as electromagnetic waves (X-rays).

[0020] When using neutrons, it is preferable to include a neutron absorber (not shown) in the heat transfer tank 102 and the reaction tank 103. The neutron absorber should preferably be a material containing elements with a large neutron reaction cross-section, such as boron, lithium, cadmium, or gadolinium. The nuclear reaction between neutrons and the neutron absorber produces alpha rays and gamma rays. Alpha rays can be used as heat (decay heat), while gamma rays can be used as radiation.

[0021] The radiation source 101 is placed inside the radiation controlled area 108 to ensure safety and is properly managed. When an operator 109 enters the radiation controlled area 108, the radiation source 101 is lowered and stored under the floor by the radiation source storage device 105. In addition, the radiation source switching device 106 closes the area where the radiation source 101 is stored in order to shield against radiation emitted from the area where the radiation source 101 is stored. The operator 109 performs these operations (controls) using the radiation source control device 107. By storing the radiation source 101, the operator 109's exposure can be reduced to almost zero, and the reaction vessel 103 and heat transfer vessel 102 can be placed inside the radiation controlled area 108 before radiation irradiation. The heat transfer vessel 102 can also be pre-assembled with the radiation source 101 and stored together with the radiation source 101.

[0022] On the other hand, when the operator 109 irradiates the substance to be irradiated 104 in the reaction vessel 103 with radiation from the radiation source 101, he operates the radiation source control device 107 to open the radiation source switch 106, brings the radiation source 101 out from under the floor, and places it inside the heat transfer tank 102. This allows the radiation source 101 to irradiate the substance to be irradiated 104 in the reaction vessel 103.

[0023] The reaction vessel 103, like the heat transfer tank 102, is a general metal container made of a metal such as stainless steel, aluminum alloy, copper, or brass. The irradiated substance 104 can be enclosed inside the reaction vessel 103, and the irradiated substance 104 can be added and removed before and after radiation irradiation. In addition to the irradiated substance 104, air or other materials may also be contained inside the reaction vessel 103. Furthermore, the shape of the irradiated substance 104 is arbitrary and does not need to match the internal shape of the reaction vessel 103.

[0024] Examples of irradiated substances 104 include biomass containing hydrocarbons or carbohydrates, plastics, forestry waste, agricultural waste, industrial waste, paper waste, or general waste. Furthermore, irradiated substances 104 also include waste containing hazardous substances such as dioxins and perfluorooctanesulfonic acid compounds (PFAS). Types of biomass include waste biomass, underutilized biomass, and resource crops. Waste biomass includes livestock manure, food waste, waste paper, pulp mill wastewater, sewage sludge, human waste sludge, construction-generated timber, sawmill residues, waste cooking oil, and fishery processing residues. Underutilized biomass includes rice straw, wheat straw, rice husks, forest residues, thinned timber, pasture grass, aquatic plants, seaweed, and seaweed. Resource crops include carbohydrate resources such as sugarcane, starch resources such as corn, and oil resources such as rapeseed.

[0025] Depending on its shape and size, it is preferable to perform mechanical processing such as cutting or crushing of the irradiated material 104 before placing it in the reaction vessel 103. It is also preferable to irradiate it with radiation before this machining (pre-irradiation) to soften the tissue. This pre-irradiation with radiation can be performed by placing the irradiated material 104 in close proximity to the radiation source 101. Doing so improves the efficiency of the machining.

[0026] The irradiated substance 104 can also be mixed with a solvent and placed inside the reaction vessel 103. Examples of solvents include water, alkaline solutions, and acidic solutions. When radiation is applied to the solvent, radicals are generated through their interaction. These radicals have the function of decomposing the irradiated substance 104, thereby improving the efficiency of radiation-induced decomposition.

[0027] Furthermore, when the temperature of the reaction tank 103 rises due to the decay heat described above, the reaction rate of the radicals increases, and the decomposition efficiency of the irradiated substance 104 by radiation improves. Further, when the temperature exceeds a certain level, the thermal decomposition of the irradiated substance 104 is promoted, and the decomposition efficiency further improves. The radiation decomposition apparatus 100 is an apparatus for improving the decomposition efficiency by radiation. For example, an apparatus such as a heater for heating the reaction tank 103 (and by extension, the irradiated substance 104), or an apparatus for performing pretreatment such as acoustic wave treatment or oxidation treatment as in the invention described in Patent Document 1 is not necessary, so the equipment scale can be reduced.

[0028] FIG. 2 is a sectional view taken along line II-II of FIG. 1. FIG. 2 shows a configuration example of the radiation source 101 and the heat transfer tank 102, the reaction tank 103, and the irradiated substance 104 in the first embodiment. In FIG. 2, the case where both the heat transfer tank 102 and the reaction tank 103 are containers (i.e., square tubes) with rectangular outer and inner shapes is illustrated. Also, a rectangular radiation source 101 is provided inside the heat transfer tank 102. And in this aspect, by bringing one surface of the reaction tank 103 with a rectangular outer shape into close contact with one surface of the heat transfer tank 102 with a rectangular outer shape, the decay heat derived from the rectangular radiation source 101 is efficiently transferred to the reaction tank 103.

[0029] In addition, although FIG. 2 shows a configuration in which one heat transfer tank 102 with a rectangular outer shape and one reaction tank 103 with a rectangular outer shape are brought into close contact, it is not limited to this. For example, another reaction tank 103 with a rectangular outer shape can be brought into close contact with another surface of one heat transfer tank 102 with a rectangular outer shape, and irradiation with radiation and heat transfer of decay heat can be performed on a plurality of reaction tanks 103 with rectangular outer shapes (not shown).

[0030] FIG. 3 is a cross-sectional view taken along line III-III of FIG. 1. FIG. 3 illustrates another configuration example of the radiation source 101 and the heat transfer tank 102, the reaction tank 103, and the irradiated substance 104 in the first embodiment. In FIG. 3, as an example, a configuration is illustrated in which a columnar radiation source 101 is provided inside a heat transfer tank 102 having a rectangular outer shape and a cylindrical cavity (inner shape). In this configuration, compared with the cross-sectional view shown in FIG. 2, although the volume of the heat transfer tank 102 increases and the permeability of radiation and heat is reduced, it is possible to combine the heat transfer tank 102 having a different outer shape with the radiation source 101. Also in this configuration, another reaction tank 103 having a rectangular outer shape can be adhered to another surface of one rectangular heat transfer tank 102, and radiation irradiation and decay heat transfer can be performed on a plurality of reaction tanks 103 having a rectangular outer shape (not shown).

[0031] FIG. 4 is a cross-sectional view taken along line IV-IV of FIG. 1. FIG. 4 illustrates another configuration example of the radiation source 101 and the heat transfer tank 102, the reaction tank 103, and the irradiated substance 104 in the first embodiment. In FIG. 4, as an example, a configuration is illustrated in which a columnar irradiated substance 104 is provided inside a reaction tank 103 having a rectangular outer shape and a cylindrical inner shape. Regarding this aspect, it may be considered that the internal structure of the reaction tank 103 having a rectangular outer shape is a cylindrical inner shape, and an irradiated substance 104 having an arbitrary shape is included in this cylindrical inner shape. Also in this configuration, it is possible to combine the radiation source 101 having a different outer shape, the heat transfer tank 102, the reaction tank 103, and the irradiated substance 104. Also in this configuration, another reaction tank 103 having a rectangular outer shape can be adhered to another surface of one heat transfer tank 102 having a rectangular outer shape, and radiation irradiation and decay heat transfer can be performed on a plurality of reaction tanks 103 having a rectangular outer shape (not shown).

[0032] FIG. 5 is an enlarged view of part V of FIG. 1. FIG. 5 illustrates a configuration example of the heat transfer tank 102 and the reaction tank 103. In the example shown in FIG. 5, the smooth surface of the heat transfer tank 102 is adhered to the smooth surface of the reaction tank 103, and decay heat from the radiation source 101 is transferred to the reaction tank 103.

[0033] Figure 6 is an enlarged view of section VI in Figure 1. Figure 6 illustrates another example of the configuration of the heat transfer tank 102 and the reaction tank 103. In the example shown in Figure 6, the surface of the heat transfer tank 102 and the surface of the reaction tank 103 are arranged in a comb-like shape that interlocks with each other. This increases the contact area between the heat transfer tank 102 and the reaction tank 103, allowing the decay heat originating from the radiation source 101 to be efficiently transferred by the reaction tank 103.

[0034] (Radiolysis Method) Next, a radiolysis method according to the first embodiment will be described. Figure 7 is a flowchart illustrating the contents of the radiolysis method according to the first embodiment. As shown in Figure 7, the radiolysis method includes an encapsulation step S10, an irradiation step S20, and an extraction step S30.

[0035] In the encapsulation step S10, the irradiated substance 104 is encapsulated in the reaction vessel 103. In the irradiation step S20, radiation emitted from the radioactive material sealed in the radiation source 101 is irradiated into the reaction vessel 103, and heat generated by the decay of the radioactive material (decay heat) is transferred to the reaction vessel 103 via the heat transfer tank 102 that covers the radiation source 101. In the removal step S30, after the reaction vessel 103 has been irradiated with a predetermined amount of radiation or after a predetermined time has elapsed, the irradiated substance 104 and the decomposed materials of the irradiated substance 104 are removed from the reaction vessel 103.

[0036] (Work Steps of the Radiolysis Apparatus) Figure 8 is a flowchart showing the work steps (S100) of the radiolysis apparatus 100 described in the first embodiment. As shown in Figure 8, first, the substance to be irradiated 104 is placed in the reaction vessel 103 (encapsulated) (S101). Next, the reaction vessel 103 is placed in the irradiation position (S102). Next, irradiation of the reaction vessel 103 with radiation and heat transfer of decay heat are started (S103). Next, it is determined whether a predetermined irradiation time has elapsed (S104). If the predetermined irradiation time has not elapsed, irradiation is continued (No in S104 → S109). If the predetermined irradiation time has elapsed, irradiation of radiation (and heat transfer of decay heat) is terminated and the radiation source 101 is stored (Yes in S104 → S105). Next, the reaction vessel 103 is removed from the irradiation position (S106). Next, the substance to be irradiated 104 and the decomposed material are removed from the reaction vessel 103 (S107). Next, useful components are extracted from the irradiated substance 104 and the decomposed substances (S108).

[0037] In addition, S104 may determine whether the reaction vessel 103 has been irradiated with a predetermined amount of radiation. In this case, if the reaction vessel 103 has not been irradiated with a predetermined amount of radiation, S109 will continue the irradiation.

[0038] The radiolysis apparatus 100 and radiolysis method described in the first embodiment above can irradiate the substance to be irradiated 104 in the reaction vessel 103 with radiation emitted from the radiation source 101 and transfer decay heat. Therefore, the radiolysis apparatus 100 and radiolysis method can efficiently decompose the substance to be irradiated 104 with a minimal equipment configuration.

[0039] [Second Embodiment] (Work Steps of the Radiolysis Apparatus) As a second embodiment, the work steps (S200) of the radiolysis apparatus 100 according to the present invention will be described. These work steps (S200) relate to more efficient operation steps of the radiolysis apparatus 100. Figure 9 is a flowchart showing the work steps (S200) of the radiolysis apparatus 100 according to the second embodiment. As shown in Figure 9, first, the substance to be irradiated 104 is put into the reaction vessel 103 (encapsulated) (S201). Next, the reaction vessel 103 is placed in the irradiation position (S202). Next, irradiation of the reaction vessel 103 with radiation and heat transfer of decay heat are started (S203). Next, it is determined whether a predetermined irradiation time has elapsed (S204). If the predetermined irradiation time has not elapsed, irradiation is continued (No in S204 → S210). If the predetermined irradiation time has elapsed, irradiation of radiation (and heat transfer of decay heat) is terminated and the radiation source 101 is stored (Yes in S204 → S205). Next, the reaction vessel 103 is removed from the irradiation position (S206). Next, the irradiated substance 104 and decomposition substances are removed from the reaction vessel 103 (S207). Next, useful components are extracted from the irradiated substance 104 and decomposition substances (S208). Next, the presence or absence of decomposable residual substances is checked for the irradiated substance 104 and decomposition substances (S209). If there are no decomposable residual substances, the process is terminated (none in S209). If there are decomposable residual substances, the residual substances are recovered (present in S209 → S211). Next, the residual substances are added to the reaction vessel 103 (encapsulated) (S212). Then, returning to S201, the irradiated substance 104 is added to the reaction vessel 103 (encapsulated), and the process from S202 onwards is repeated.

[0040] In addition, S204 may determine whether the reaction vessel 103 has been irradiated with a predetermined amount of radiation. In this case, S210 will continue the irradiation if the reaction vessel 103 has not been irradiated with a predetermined amount of radiation.

[0041] In the work step (S200) of the radiolysis apparatus 100 described above as the second embodiment, useful components can be extracted more efficiently from the irradiated substance 104.

[0042] [Third Embodiment] A radiation decomposition device 100 according to the third embodiment of the present invention will be described. The third embodiment relates to a radiation decomposition device 100 that can more efficiently decompose the irradiated substance 104. FIG. 10 is a longitudinal sectional view for explaining a configuration example of the reaction tank 103 of the radiation decomposition device 100 according to the third embodiment. Note that FIG. 10 is a longitudinal sectional view showing a plane perpendicular to the radiation irradiation direction.

[0043] As shown in FIG. 10, the radiation decomposition device 100 according to the third embodiment includes an irradiated substance 104 and a Compton electron generating substance 117 inside the reaction tank 103. In FIG. 10, a rod-shaped Compton electron generating substance 117 is shown. The Compton electron generating substance 117 is a substance that emits electrons to the outside of the Compton electron generating substance 117 when irradiated with radiation. When gamma rays or X-rays enter the Compton electron generating substance 117, Compton electrons or secondary electrons further ejected by the Compton electrons are emitted by the Compton reaction with the elements contained in the Compton electron generating substance 117.

[0044] When these electrons interact with the irradiated substance 104, the decomposition of the irradiated substance 104 is promoted. Or, when these electrons interact with the solvent in which the irradiated substance 104 is mixed, radicals are generated, and the decomposition of the irradiated substance 104 is promoted by the radicals.

[0045] FIG. 11 is a graph for explaining the relationship between the effective atomic number Z eff of the Compton electron generating substance 117 and the Compton cross section ε eff . The Compton cross section ε eff is basically proportional to the atomic number Z. Therefore, like the straight line 118 represented by the Z eff - ε eff relational expression (the following formula (1)), the Compton cross section ε eff is proportional to the effective atomic number Z eff of the Compton electron generating substance 117.

[0046] Z eff = ε eff / (NA × f(E)) ... (1) (Here, Z eff : The effective atomic number of Compton electron-generating material 117, ε eff : Compton cross-section of Compton electron generating material 117, NA: number density of atoms, f(E): function of incident gamma-ray energy (depending on the properties of radiation source 101).

[0047] As shown in Figure 11, the material of the Compton electron generating material 117 that achieves efficient radiolysis has an effective atomic number of Z eff A large value is desirable. As for the material of the Compton electron generating material 117, common materials include glass, concrete, stainless steel, iron, lead, tungsten, copper, gold, water or alkaline solutions that can be used as solvents, and materials with a higher density than the irradiated material 104.

[0048] Figure 12 shows the effective thickness t of the Compton electron generating material 117. eff This graph illustrates the relationship between the probability of existence p of Compton electrons in a material. Compton electrons, generated by the interaction between radiation and the Compton electron generating material 117, fly according to their kinetic energy. The maximum energy of a Compton electron is determined by the energy of the interacting radiation and the emission angle of the Compton electron. Therefore, in Figure 12, t eff As shown by the curve 119 represented by the -p relation (equation (2) below), the effective thickness t of the Compton electron generating material 117 eff The probability of Compton electrons being present, p, can be determined, and the maximum range 121 of Compton electrons can be known in advance.

[0049] p(t) eff ) = N(t eff ) / N(0)=exp(-μt eff ) ... (2) (Here, p(t eff ): Effective thickness t of Compton electron generating material 117 eff The probability of Compton electrons being found in a material, t eff: Effective thickness of Compton electron generating material 117, N(t): Number of electrons at thickness t, N(0): Number of electrons at thickness 0 (number of generated electrons), μ: Mass attenuation constant in Compton electron generating material 117.

[0050] Figure 13 shows the effective thickness t of the Compton electron generating material 117. eff This graph illustrates the relationship between the Compton electron emission amount A and the Compton cross-section ε. eff and the effective thickness t of the Compton electron generating material 117 eff , determined by the probability of existence p of Compton electrons. Figure 13 t eff As shown by the curve 120 represented by relation A (equation (3) below), the effective thickness t of the Compton electron generating material 117 is generally eff As we approach t, ​​the amount of electrons emitted from the Compton electron generating material 117 asymptotically approaches the thickness t eff Saturation occurs when it exceeds a certain value. From this, the effective thickness t of the Compton electron generating material 117 eff It is desirable to set this near the maximum range 121 of Compton electrons. The thickness of the Compton electron generating material 117 is the effective thickness t of the Compton electron generating material 117. eff If this value is exceeded, the volume ratio of the irradiated substance 104 to the Compton electron generating substance 117 inside the reaction vessel 103 will increase, potentially reducing the decomposition efficiency.

[0051] A(t) = ∫N(t-τ)g(τ)dτ ... (3) g(τ) = exp(-μτ) (where, N(t): number of Compton electrons at thickness t, t: thickness of the Compton electron generating material 117, τ: thickness of a certain region of the Compton electron generating material 117, μ: mass attenuation constant in the Compton electron generating material 117.)

[0052] Figure 14 is a longitudinal cross-sectional view illustrating another configuration example of the reaction vessel 103 of the radiolysis apparatus 100 according to the third embodiment. Note that Figure 14 is a longitudinal cross-sectional view showing a plane perpendicular to the direction of radiation irradiation. In the configuration example shown in Figure 10 above, a rod-shaped Compton electron generating material 117 was shown, but as shown in Figure 14, a plate-shaped Compton electron generating material 117 may also be arranged. In this case, the plate-shaped Compton electron generating material 117 should be arranged so that it can receive radiation irradiation over a wide area. In this way, Compton electrons are generated over a wide area, so the irradiated material 104 can be decomposed more efficiently.

[0053] Figure 15 is a longitudinal cross-sectional view illustrating another configuration example of the reaction vessel 103 of the radiolysis apparatus 100 according to the third embodiment. Figure 15 shows a mesh-like Compton electron generating material 117 having through holes arranged in the reaction vessel 103. In Figure 15, a mesh with circular through holes is shown as an example, but the shape is arbitrary. By making the Compton electron generating material 117 mesh-like in this way, the irradiated substance 104 and solvent can flow inside the reaction vessel 103. Therefore, contact between the irradiated substance 104 and solvent and Compton electrons is promoted, and the irradiated substance 104 can be decomposed more efficiently.

[0054] Figure 16 is a longitudinal cross-sectional view illustrating another configuration example of the reaction vessel 103 of the radiolysis apparatus 100 according to the third embodiment. Figure 16 shows a configuration in which spherical Compton electron generating material 117 is placed in the reaction vessel 103. As shown in Figure 16, in this configuration, the irradiated material 104 and the spherical Compton electron generating material 117 can be mixed. This causes Compton electrons to be generated at random locations within the reaction vessel 103. Therefore, the irradiated material 104 can be decomposed uniformly, evenly, and efficiently.

[0055] Figure 17 is a longitudinal cross-sectional view illustrating another configuration example of the reaction vessel 103 of the radiolysis apparatus 100 according to the third embodiment. Figure 17 includes a stirring unit 125 that can stir the spherical Compton electron generating material 117 shown in Figure 16 together with the irradiated material 104 inside the reaction vessel 103 even during radiation irradiation. In this configuration example, by operating the stirring unit 125 during radiation irradiation, the irradiated material 104 and the spherical Compton electron generating material 117 can be made to flow. This prevents the arrangement of the spherical Compton electron generating material 117 inside the reaction vessel 103 from being uneven. As a result, Compton electrons can come into contact with the irradiated material 104 more evenly and uniformly, and the irradiated material 104 can be decomposed more efficiently. As an example of the stirring unit 125, a stirring blade that can be rotated by an actuator such as a motor (not shown) can be cited. Furthermore, the stirring section 125 may be, for example, a stirring bar made of magnetic material that rotates inside the reaction vessel 103 by rotating a magnetic field generated outside the reaction vessel 103. Specifically, the stirring section 125 may be, for example, a stirrer bar rotated by a magnetic stirrer.

[0056] The radiolysis apparatus 100 according to the third embodiment described above is equipped with a Compton electron generating material 117, which allows for even more efficient decomposition of the irradiated substance 104. As a result, the radiolysis apparatus 100 can efficiently extract useful components.

[0057] [Fourth Embodiment] A radiolysis apparatus 100 according to the fourth embodiment of the present invention will be described. The fourth embodiment relates to a radiolysis apparatus 100 that can decompose the irradiated substance 104 with greater safety and efficiency.

[0058] Figure 18 is a schematic cross-sectional view showing an example of the configuration of a radiolysis apparatus 100 according to the fourth embodiment. As shown in Figure 18, the radiolysis apparatus 100 according to the fourth embodiment is provided on the surface of the reaction vessel 103 with a thermometer 126 for measuring the temperature of the reaction vessel 103, and a temperature monitoring device 127 for recording, displaying, and monitoring the temperature (measured value) measured by the thermometer 126, compared to the radiolysis apparatus 100 shown in the first embodiment. The temperature shown by the temperature monitoring device 127 can be constantly monitored by the operator 109.

[0059] Figure 19 is a temperature monitoring chart of the reaction vessel 103. In this figure, the horizontal axis represents time and the vertical axis represents temperature. As shown in Figure 19, the reaction vessel temperature 131 begins to rise from the radiation irradiation start time 129. Radiation irradiation is stopped before the reaction vessel temperature 131 exceeds the control threshold 128 and reaches the excess temperature range 132. After the radiation irradiation stop time 130, the reaction vessel temperature 131 naturally decreases due to air cooling, etc. The temperature rise range due to the radiation source 101 can be predicted in advance based on the intensity of the radiation source 101 and the ambient temperature. It is desirable to design the arrangement, configuration, and specifications of the heat transfer tank 102 and the reaction vessel 103 so that radiation irradiation and decay heat transfer can continue within a preset normal temperature range 133 (i.e., not exceeding the control threshold 128), as shown in Figure 19.

[0060] Figure 20 is a flowchart showing the work steps (S300) of the radiolysis apparatus 100 according to the fourth embodiment. As shown in Figure 20, first, the substance to be irradiated 104 is placed in the reaction vessel 103 (encapsulated) (S301). Next, the reaction vessel 103 is placed in the irradiation position (S302). Next, irradiation of the reaction vessel 103 with radiation and heat transfer of decay heat are started (S303). Next, it is confirmed that the temperature of the reaction vessel 103 is below the control value (control threshold 128) (S304). If it is below the control value, it is determined whether a predetermined irradiation time has elapsed (Yes in S304 → S305). If the predetermined irradiation time has not elapsed, the process returns to S305 to continue irradiation and determine whether the irradiation time has elapsed (No in S305 → S313 → S305). If the predetermined irradiation time has elapsed, radiation irradiation (and heat transfer of decay heat) is terminated and the radiation source 101 is stored (Yes in S305 → S306). Next, the reaction vessel 103 is removed from the irradiation position (S307). Next, the irradiated substance 104 and decomposed substances are removed from the reaction vessel 103 (S308). Next, useful components are extracted from the irradiated substance 104 and decomposed substances (S309). In S304, if the control value is exceeded, the radiation source 101 is stored (No in S304 → S310). Next, it is confirmed that the temperature of the reaction vessel 103 is below the control value (S311). If the temperature of the reaction vessel 103 exceeds the control value, the radiation source 101 is stored and the system waits, the cooling of the reaction vessel 103 continues, and the process is repeated again, returning to S311 (No in S311 → S312 → S311). If the temperature of the reaction vessel 103 is below the control value, the system returns to S303 and begins irradiation of the reaction vessel 103 with radiation and transfer of decay heat (Yes in S311 → S303).

[0061] In addition, step S305 may determine whether the reaction vessel 103 has been irradiated with a predetermined amount of radiation. In this case, step S313 will continue the irradiation if the reaction vessel 103 has not been irradiated with a predetermined amount of radiation.

[0062] In the fourth embodiment described above, the radiolysis apparatus 100 is equipped with the aforementioned thermometer 126 and temperature monitoring device 127 in the reaction vessel 103, thus preventing the temperature of the reaction vessel 103, the temperature of the irradiated substance 104, and / or the temperature of the entire apparatus from becoming too high. Therefore, the radiolysis apparatus 100 described in the fourth embodiment can prevent damage to the reaction vessel 103 and the apparatus due to heat, thereby increasing safety. Furthermore, in this embodiment, the heating of the irradiated substance 104 is carried out within an appropriate range, so the irradiated substance 104 can be efficiently decomposed and useful components can be extracted.

[0063] [Fifth Embodiment] A radiolysis apparatus 100 according to the fifth embodiment of the present invention will now be described. The fifth embodiment relates to a radiolysis apparatus 100 that can more efficiently decompose the irradiated substance 104 by radiation by efficiently transferring the decay heat from the radiation source 101 to the irradiated substance 104.

[0064] Figure 21 is a schematic cross-sectional view showing an example of the configuration of a radiolysis apparatus 100 according to the fifth embodiment. As shown in Figure 21, the radiolysis apparatus 100 according to the fifth embodiment is provided with a heat-insulating tank 134 that encloses (covers) and insulates the heat transfer tank 102 and the reaction tank 103, compared to the radiolysis apparatus 100 shown in the fourth embodiment. In this embodiment, when the heating temperature of the reaction tank 103 due to the decay heat of the radiation source 101 is low, the heat-insulating tank 134 can be used to reduce the amount of waste heat. Therefore, the radiolysis apparatus 100 according to the fifth embodiment can raise the temperature of the reaction tank 103 and improve the decomposition efficiency of the irradiated substance 104. As described above, the radiolysis apparatus 100 according to the fifth embodiment is provided with the heat-insulating tank 134, so that the decay heat from the radiation source 101 can be effectively utilized and heat can be efficiently transferred to the irradiated substance 104. Therefore, the radiolysis apparatus 100 according to the fifth embodiment can decompose the irradiated substance 104 even more efficiently.

[0065] Although the radiolysis apparatus 100 and radiolysis method according to the present invention have been described in detail above with reference to embodiments, the present invention is not limited to the embodiments described above and includes various modifications. For example, the embodiments described above are described in detail for the purpose of explaining the present invention in an easy-to-understand manner and are not necessarily limited to those having all the configurations described. Furthermore, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. In addition, it is possible to add, delete, or replace parts of the configuration of each embodiment with other configurations.

[0066] 100 Radiolysis apparatus 101 Radiation source 102 Heat transfer tank 103 Reaction tank 104 Irradiated material 105 Source storage device 107 Source control device 117 Compton electron generating material 126 Thermometer 127 Temperature monitoring device 134 Insulation tank

Claims

1. A radiolysis apparatus comprising: a radiation source that irradiates with radiation emitted from a sealed radioactive material; a reaction vessel containing the material to be irradiated; and a heat transfer vessel that covers the radiation source and transfers heat generated by the decay of the radioactive material to the reaction vessel.

2. A radiolysis apparatus according to claim 1, characterized in that the radiation source is a radiation source formed from spent nuclear fuel or a vitrified body containing fission products extracted from spent nuclear fuel, a radiation source containing fission products extracted from spent nuclear fuel, a radiation source containing Co-60, a radiation source containing Cs-137, or high-level radioactive waste liquid.

3. A radiolysis apparatus according to claim 1, characterized in that the radiation source emits gamma rays, bremsstrahlung radiation, or X-rays.

4. A radiolysis apparatus according to claim 1, characterized in that the irradiated substance is biomass containing hydrocarbons or carbohydrates, plastics, forestry waste, agricultural waste, industrial waste, paper waste, or general waste.

5. A radiolysis apparatus according to claim 1, characterized in that the reaction vessel contains a solvent.

6. A radiolysis apparatus according to claim 1, comprising: a source storage device for moving a radiation source in and out of a radiation controlled area; and a source control device for controlling the source storage device.

7. A radiolysis apparatus according to claim 1, characterized in that the reaction vessel contains a Compton electron generating material.

8. A radiolysis apparatus according to claim 1, comprising: a thermometer for measuring the temperature of the reaction vessel; and a temperature monitoring device for recording and displaying the measured value of the thermometer.

9. A radiolysis apparatus according to claim 1, characterized in that it comprises a heating tank enclosing the radiation source and the reaction vessel.

10. A radiolysis method characterized by comprising: an encapsulation step of encapsulating the substance to be irradiated in a reaction vessel; an irradiation step of irradiating the reaction vessel with radiation emitted from a radioactive material sealed in a radiation source, and transferring the heat generated by the decay of the radioactive material to the reaction vessel via a heat transfer tank covering the radiation source; and a removal step of removing the substance to be irradiated and the decomposed substances of the irradiated substance from the reaction vessel after irradiating the reaction vessel with a predetermined amount of radiation or after a predetermined time has elapsed.

Images