Radiolysis apparatus and radiolysis method

Abstract

To provide a radiolysis apparatus and radiolysis method that can efficiently decompose irradiated materials while keeping the equipment size as small as possible. [Solution] The radiolysis apparatus 100 according to the present invention is characterized by comprising: a radiation source 101 that irradiates with radiation emitted from a sealed radioactive material; a reaction vessel 103 that encloses the material to be irradiated 104; and a heat transfer vessel 102 that covers the radiation source 101 and transfers the heat generated by the decay of the radioactive material to the reaction vessel 103. The radiation source 101 is preferably 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.

Description

[Technical Field]

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

[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 agriculture, environment, and resource fields, 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 perfluorinated compounds (PFAS). Furthermore, radiolysis equipment is required to improve economic efficiency by minimizing the equipment used while improving 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 alter 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 features a facility in which, at least a portion of the area surrounding 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. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2019-150824 [Patent Document 2] Japanese Patent Publication No. 2001-91695 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] In radiolysis devices, 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 enhances the efficiency of biomass pretreatment by incorporating a process of pretreatment of biomass raw materials using one or more means such as radiation irradiation, sonic treatment, oxidation, thermal decomposition, or steam explosion. In other words, the invention described in Patent Document 1 requires the configuration of the apparatus using multiple methods in order to increase efficiency, which necessitates the construction of large-scale facilities and the complex operation of those facilities. Furthermore, the invention described in Patent Document 1 requires not only simply increasing the amount of equipment, but also the configuration of the apparatus and the method for efficiently decomposing the irradiated material.

[0009] The invention described in Patent Document 2 utilizes radiation emitted from high-dose radioactive waste to decompose chlorine-based hazardous substances, thereby 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 radioactivity level, is generally done during the radiation source manufacturing stage before its introduction into the facility, making it difficult to adjust the radioactivity level 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 irradiation dose. Therefore, efficiently decomposing the irradiated material is difficult.

[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. [Means for solving the problem]

[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. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a radiolysis apparatus and a radiolysis method that can efficiently decompose irradiated material while keeping the equipment size as small as possible. Other issues, configurations, and effects not mentioned above will be revealed by the following description of embodiments. Further features related to the present invention will be revealed by the description herein and the accompanying drawings. [Brief explanation of the drawing]

[0013] [Figure 1] It is a schematic cross-sectional view showing a configuration example of the radiation decomposition device 100 according to the first embodiment. [Figure 2] It is a cross-sectional view taken along line II-II of FIG. 1. [Figure 3] It is a cross-sectional view taken along line III-III of FIG. 1. [Figure 4] It is a cross-sectional view taken along line IV-IV of FIG. 1. [Figure 5] It is an enlarged view of part V of FIG. 1. [Figure 6] It is an enlarged view of part VI of FIG. 1. [Figure 7] It is a flowchart for explaining the content of the radiation decomposition method according to the first embodiment. [Figure 8] It is a flowchart showing the working steps (S100) of the radiation decomposition device 100 described in the first embodiment. [Figure 9] It is a flowchart showing the working steps (S200) of the radiation decomposition device 100 according to the second embodiment. [Figure 10] It 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. [Figure 11] It is a graph for explaining the relationship between the effective atomic number Zeff and the Compton cross-section εeff of the Compton electron generating substance 117. [Figure 12] It is a graph for explaining the relationship between the effective thickness teff of the Compton electron generating substance 117 and the probability p of the presence of Compton electrons in the substance. [Figure 13] It is a graph for explaining the relationship between the effective thickness teff of the Compton electron generating substance 117 and the emission amount A of Compton electrons. [Figure 14] It is a longitudinal sectional view for explaining another configuration example of the reaction tank 103 of the radiation decomposition device 100 according to the third embodiment. [Figure 15] It is a longitudinal sectional view for explaining another configuration example of the reaction tank 103 of the radiation decomposition device 100 according to the third embodiment. [Figure 16]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. [Figure 17] 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. [Figure 18] This is a schematic cross-sectional view showing an example of the configuration of a radiolysis apparatus 100 according to the fourth embodiment. [Figure 19] This is a temperature monitoring chart for reaction vessel 103. [Figure 20] This is a flowchart of the work steps (S300) of the radiolysis apparatus 100 according to the fourth embodiment. [Figure 21] This is a schematic cross-sectional view showing an example of the configuration of a radiolysis apparatus 100 according to the fifth embodiment. [Modes for carrying out the invention]

[0014] This invention relates to a technology for decomposing irradiated materials by radiation, and is based on new findings obtained through various studies in order to efficiently decompose irradiated materials with a minimal equipment configuration. Hereinafter, a radiolysis apparatus and radiolysis method according to one embodiment of the present invention 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 descriptions may be omitted. Furthermore, the present 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 device) Referring to Figures 1 to 7, a radiolysis apparatus 100 and a radiolysis method according to the first embodiment of the present invention will be described. Figure 1 is a schematic cross-sectional view showing an example of the configuration of a radiolysis apparatus 100 according to the first embodiment. As shown in Figure 1, the radiolysis apparatus 100 according to the first embodiment includes a radiation source 101, a heat transfer tank 102, and a reaction tank 103. The radiation source 101 irradiates the radioactive material with radiation emitted from the sealed radioactive material. The reaction vessel 103 contains the material to be irradiated 104. The heat transfer vessel 102 covers the radiation source 101 and transfers the heat generated by the decay of the radioactive material (decay heat) to the reaction vessel 103. Furthermore, the radiolysis apparatus 100 includes a source storage device 105, a source switching device 106, a source control device 107, and a radiation controlled area 108. The operator 109 operates the radiation source 101 using the source control device 107, which connects the source storage device 105 and the 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] The radiation source 101 is surrounded by a heat transfer tank 102. The heat transfer tank 102 is a common metal container made of materials such as stainless steel, aluminum alloy, copper, or brass. Alpha and beta rays are shielded by the thickness of the heat transfer tank 102, 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 tank 103. Gamma rays and X-rays are both electromagnetic waves (light), but gamma rays are generated inside the atomic nucleus, while X-rays are generated outside the atomic nucleus. Bremsstrahlung radiation occurs when a fast-moving charged particle, such as an electron, passes near the atomic nucleus and is slowed down by the electric field, and the energy lost in the 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 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 vessel 102, is a general metal container made of 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 may also include waste containing hazardous substances such as dioxins or perfluorinated compounds (PFAS). Biomass can be categorized into 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 sugar 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 in 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, as the temperature of the reaction vessel 103 rises due to the decay heat described above, the reaction rate of radicals improves, and the efficiency of decomposition of the irradiated substance 104 by radiation improves. Moreover, once a certain temperature is exceeded, the thermal decomposition of the irradiated substance 104 is accelerated, further improving the decomposition efficiency. The radiolysis apparatus 100 does not require devices to improve the decomposition efficiency by radiation, such as heaters for heating the reaction vessel 103 (and consequently the irradiated substance 104), or devices for pre-treatment such as sonic treatment or oxidation treatment, as described in Patent Document 1, so the scale of the equipment can be reduced.

[0028] Figure 2 is a cross-sectional view taken along line II-II of Figure 1. Figure 2 illustrates one example configuration of the radiation source 101 and heat transfer tank 102, and the reaction tank 103 and irradiated material 104 in the first embodiment. Figure 2 illustrates a case where both the heat transfer tank 102 and the reaction vessel 103 are rectangular containers (i.e., rectangular tubes) with rectangular external and internal shapes. A rectangular radiation source 101 is provided inside the heat transfer tank 102. In this embodiment, by closely attaching one side of the rectangular-shaped reaction vessel 103 to one side of the rectangular-shaped heat transfer tank 102, the decay heat originating from the rectangular radiation source 101 is efficiently transferred to the reaction vessel 103.

[0029] Although Figure 2 shows a configuration in which one rectangular heat transfer tank 102 and one rectangular reaction tank 103 are in close contact, the configuration is not limited to this. For example, one rectangular reaction tank 103 can be attached to another side of one rectangular heat transfer tank 102, allowing multiple rectangular reaction tanks 103 to be irradiated with radiation and undergo heat transfer of decay heat (not shown).

[0030] Figure 3 is a cross-sectional view taken along line III-III of Figure 1. Figure 3 illustrates another configuration example of the radiation source 101 and heat transfer tank 102, and the reaction tank 103 and irradiated material 104 in the first embodiment. Figure 3 illustrates an example configuration in which a cylindrical radiation source 101 is placed inside a heat transfer tank 102 having a rectangular outer shape and a cylindrical cavity (inner shape). In this configuration, the volume of the heat transfer tank 102 is increased compared to the cross-sectional view shown in Figure 2, so although the transmission of radiation and heat is reduced, it becomes possible to combine a heat transfer tank 102 and a radiation source 101 having different outer shapes. In this configuration as well, other rectangular-shaped reaction vessels 103 can be placed in close contact with another side of one rectangular-shaped heat transfer vessel 102, allowing multiple rectangular-shaped reaction vessels 103 to be irradiated with radiation and undergo heat transfer of decay heat (not shown).

[0031] Figure 4 is a cross-sectional view taken along line IV-IV of Figure 1. Figure 4 illustrates another configuration example of the radiation source 101 and heat transfer tank 102, and the reaction tank 103 and irradiated material 104 in the first embodiment. Figure 4 illustrates an example configuration in which a cylindrical irradiated material 104 is placed inside a reaction vessel 103 having a rectangular outer shape and a cylindrical inner shape. In this embodiment, it may also be considered that the internal structure of the rectangular outer shape of the reaction vessel 103 is a cylindrical inner shape, and that the irradiated material 104 of any shape is enclosed within this cylindrical inner shape. In this configuration as well, it is possible to combine a radiation source 101 having a different outer shape, a heat transfer tank 102, a reaction vessel 103, and the irradiated material 104. In this configuration as well, other rectangular reaction vessels 103 can be placed in close contact with another rectangular heat transfer vessel 102, allowing multiple rectangular reaction vessels 103 to be irradiated with radiation and subjected to decay heat transfer (not shown).

[0032] Figure 5 is an enlarged view of section V in Figure 1. Figure 5 illustrates one example configuration of the heat transfer tank 102 and the reaction tank 103. In the example shown in Figure 5, the smooth surface of the heat transfer tank 102 and the smooth surface of the reaction tank 103 are brought into close contact, and the decay heat originating from the radiation source 101 is transferred to the reaction tank 103.

[0033] Figure 6 is an enlarged view of section VI of 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, the 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 comprises 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 irradiation step S20, radiation emitted from the radioactive material sealed in the radiation source 101 is irradiated onto 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 substances of the irradiated substance 104 are removed from the reaction vessel 103.

[0036] (Operating 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 irradiated substance 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 with 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 irradiated substance 104 and decomposed substances are removed from the reaction vessel 103 (S107). Next, useful components are extracted from the irradiated substance 104 and decomposed substances (S108).

[0037] Alternatively, 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] (Operating steps of the radiolysis apparatus) As a second embodiment, a work step (S200) of the radiolysis apparatus 100 according to the present invention will be described. This work step (S200) relates to a more efficient operation step of the radiolysis apparatus 100. Figure 9 is a flowchart showing the work step (S200) of the radiolysis apparatus 100 according to the second embodiment. As shown in Figure 9, first, the irradiated substance 104 is placed in 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 with 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 decomposed substances are removed from the reaction vessel 103 (S207). Next, useful components are extracted from the irradiated substance 104 and decomposed substances (S208). Next, the presence or absence of decomposable residues is checked for the irradiated substance 104 and the decomposition substance (S209). If there are no decomposable residues, the process is terminated (none in S209). If there are decomposable residues, the residues are recovered (present in S209 → S211). Next, the residues 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 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 radiolysis apparatus 100 according to a third embodiment of the present invention will now be described. The third embodiment relates to a radiolysis apparatus 100 that can decompose the irradiated substance 104 even more efficiently. FIG. 10 is a longitudinal sectional view for explaining a configuration example of a reaction vessel 103 of a radiation decomposition apparatus 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 apparatus 100 according to the third embodiment includes an irradiated substance 104 and a Compton electron generating substance 117 inside a reaction vessel 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 are incident on the Compton electron generating substance 117, Compton electrons or secondary electrons further ejected by the Compton electrons are emitted by Compton reactions with 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. Alternatively, when these electrons interact with a 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 a straight line 118 represented by the Z eff -ε eff relationship formula (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 effThe effective atomic number of Compton electron-generating material 117, ε eff Compton cross-sectional area of ​​Compton electron generating material 117, NA: Number density of atoms, f(E): A function of the incident gamma-ray energy (dependent on the properties of radiation source 101). (That is the case.)

[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. Common materials for the Compton electron generating material 117 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 electron existence p can be determined for this, and the maximum range of Compton electrons, 121, 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 existing in a material, t effEffective thickness of Compton electron-generating material 117, N(t): Number of electrons at thickness t, N(0): Number of electrons at a thickness of 0 (number of electrons generated) μ: Mass attenuation constant in Compton electron-generating material 117, (That is the case.)

[0050] Figure 13 shows the effective thickness t of 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 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 the -A relation (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 t, and the thickness 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) (Here, N(t): Number of Compton electrons at thickness t, t: Thickness of Compton electron-generating material 117, τ: Thickness of a region in Compton electron-generating material 117, μ: Mass attenuation constant in Compton electron-generating material 117, (That is the case.)

[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, a rod-shaped Compton electron generating material 117 is shown. However, 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 be irradiated with radiation over a wide area. This allows for the generation of Compton electrons over a wide area, thus enabling more efficient decomposition of the irradiated material 104.

[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 spherical Compton electron generating material 117 from being unevenly distributed inside the reaction vessel 103. 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. The stirring unit 125 can be, for example, a stirring blade that can be rotated by an actuator such as a motor (not shown). 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 starter 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 a fourth embodiment of the present invention will now 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. 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 for 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 the 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 irradiated substance 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 the predetermined irradiation time has elapsed (Yes in S304 → S305). If the predetermined irradiation time has not elapsed, return to S305 and continue irradiation, and determine whether the irradiation time has elapsed (No in S305 → S313 → S305). If the predetermined irradiation time has elapsed, irradiation with radiation (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 the decomposed substances are removed from the reaction vessel 103 (S308). Next, useful components are extracted from the irradiated substance 104 and the 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 cooling of the reaction vessel 103 is continued, and the process is repeated by returning to S311 (No in S311 → S312 → S311). If the temperature of the reaction vessel 103 is below the control value, the process returns to S303 and radiation irradiation and decay heat transfer to the reaction vessel 103 are started (Yes in S311 → S303).

[0061] Alternatively, S305 may determine whether the reaction vessel 103 has been irradiated with a predetermined amount of radiation. In this case, S313 will continue 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 a 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 discharge can be reduced by using the heat-insulating tank 134. Therefore, the radiolysis apparatus 100 according to the fifth embodiment can raise the temperature of the reaction tank 103 and increase the decomposition efficiency of the irradiated substance 104. The radiolysis apparatus 100 described in the fifth embodiment above is equipped with the aforementioned heat-retaining tank 134, which allows for effective utilization of decay heat from the radiation source 101 and efficient heat transfer to the irradiated material 104. Therefore, the radiolysis apparatus 100 according to the fifth embodiment can decompose the irradiated material 104 even more efficiently.

[0065] As described above, the radiation decomposition apparatus 100 and the radiation decomposition method according to the present invention have been described in detail by way of embodiments. However, the present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Also, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, for a part of the configuration of each embodiment, addition, deletion, or replacement with another configuration is possible.

Explanation of Reference Numerals

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

Claims

1. A radiation source that irradiates with radiation emitted from sealed radioactive material, A reaction vessel containing the irradiated substance, A heat transfer tank that covers the radiation source and transfers the heat generated by the decay of the radioactive material to the reaction vessel, A radiolysis apparatus characterized by being equipped with the following features.

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

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

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

6. A radiolysis apparatus according to claim 1, A radiation source storage device for moving the aforementioned radiation source in and out of the radiation controlled area, A radiation source control device that controls the aforementioned radiation source storage device, A radiolysis apparatus characterized by being equipped with the following features.

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

8. A radiolysis apparatus according to claim 1, A thermometer for measuring the temperature of the reaction vessel, A temperature monitoring device that records and displays the measured value of the aforementioned thermometer, A radiolysis apparatus characterized by being equipped with the following features.

9. A radiolysis apparatus according to claim 1, A radiolysis apparatus characterized by comprising a heating tank that encloses the aforementioned radiation source and the aforementioned reaction vessel.

10. The encapsulation step involves placing the irradiated substance inside the reaction vessel, An irradiation step in which radiation emitted from a radioactive material sealed in a radiation source is irradiated onto the reaction vessel, and heat generated by the decay of the radioactive material is transferred to the reaction vessel via a heat transfer tank covering the radiation source, After irradiating the reaction vessel with a predetermined amount of radiation or after a predetermined time has elapsed, a removal step is taken to remove the irradiated substance and the decomposition substances of the irradiated substance from the reaction vessel. A method for radiolysis characterized by having the following features.

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