Nuclide processing method and nuclide processing system

Abstract

The objective is to support a larger amount of the radionuclide to be treated on the reaction medium of perovskite oxide than is possible through electrodeposition. [Solution] The radionuclide treatment method according to the present disclosure involves (S1) supporting the radionuclide to be treated on a titanium-containing perovskite oxide by sintering, and (S2) heating the titanium-containing perovskite oxide on which the radionuclide to be treated is supported together with a hydride donor in a vacuum or in an inert gas atmosphere, thereby replacing some of the oxygen sites of the titanium-containing perovskite oxide with hydrogen ions to form a titanium-containing perovskite oxyhydride on which the radionuclide to be treated is supported.

Description

Technical Field

[0001] The present disclosure relates to a nuclide processing method and a nuclide processing system.

Background Art

[0002] To promote the "nuclear fuel cycle" that reprocesses spent fuel generated from nuclear power generation, reuses the extracted uranium and plutonium, and reduces the amount of waste, a technology for safely processing and storing liquid waste with high radioactivity levels is required. There is a need for nuclide processing as a technology to mitigate the processing risks of high-level radioactive waste.

[0003] Patent Document 1 discloses a nuclide processing method using a nuclide conversion catalyst that is an oxyhydride in which nuclide conversion of a nuclide conversion target proceeds.

[0004] In Patent Document 1, a nuclide conversion catalyst in which the oxygen sites of a perovskite oxide are substituted with hydride is used, and after the hydride-substituted oxygen sites are substituted with deuteride, the nuclide conversion target is supported on the nuclide conversion catalyst by electrodeposition.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, electrodeposition has a problem that the amount of nuclide conversion target that can be supported on the nuclide conversion catalyst is small, and the process must be performed repeatedly.

[0007] The present disclosure has been made in view of such circumstances, and an object thereof is to provide a nuclide conversion method and a nuclide conversion system that allow a larger amount of target nuclide to be supported on a reaction medium made of a perovskite oxide than by electrodeposition. [Means for Solving the Problems]

[0008] In order to solve the above problems, the nuclide processing method and nuclide processing system of the present disclosure adopt the following means.

[0009] The present disclosure provides a nuclide processing method, comprising: supporting a target nuclide to be processed on a titanium-containing perovskite oxide by sintering; heating the titanium-containing perovskite oxide supporting the target nuclide to be processed together with a hydride donor in a vacuum or an inert gas atmosphere; and substituting part of oxygen sites of the titanium-containing perovskite oxide with hydrogen ions to form a titanium-containing perovskite oxyhydrate supporting the target nuclide to be processed.

[0010] The present disclosure provides a nuclide processing system, comprising: a sintered body production unit for producing a sintered body in which a target nuclide to be processed is supported on a titanium-containing perovskite oxide; and a hydride substitution unit that accommodates a mixture of the sintered body and a hydride donor, and heats the mixture to perform hydride substitution. [Effects of the Invention]

[0011] According to the present disclosure, by supporting the target nuclide to be processed on the titanium-containing perovskite oxide by sintering, the supported amount can be increased as compared with the case where the nuclide is supported by electrodeposition. [Brief Description of the Drawings]

[0012] [Figure 1] It is a diagram showing the procedure of the nuclide processing method according to the first embodiment. [Figure 2] It is a schematic diagram of the hydride substitution unit for explaining the procedure of hydride substitution. [Figure 3] It is a diagram showing a modification of the procedure of the nuclide processing method according to the first embodiment. [Figure 4] It is a schematic cross-sectional view of a tubular furnace. [Figure 5] It is a diagram showing the crystal structure of a sintered body obtained by mixing BaTiO3 and Cs2CO3 and performing sintering. [Figure 6] This figure shows the crystal structure of a sintered body obtained by sintering a mixture of BaCO3 and TiO2 with Cs2CO3. [Figure 7] This is a flowchart of the radionuclide processing system according to the third embodiment. [Figure 8] This is a schematic diagram of the electrodeposition apparatus used in the manufacture of Comparative Example 4. [Modes for carrying out the invention]

[0013] An embodiment of the radionuclide processing method and radionuclide processing system relating to this disclosure will be described below with reference to the drawings.

[0014] [First Embodiment] Figure 1 shows the procedure of the radionuclide treatment method according to this embodiment. The radionuclide treatment method according to this embodiment comprises (S1) a step of manufacturing a radionuclide-supported reaction medium, (S2) a hydride substitution step, and (S3) a washing step.

[0015] (S1) Production of the radionuclide-supported reaction medium The radionuclides to be treated are mixed into the reaction medium and sintered. Sintering is carried out by heat treatment at 850°C to 1000°C for 2 to 24 hours in an inert gas atmosphere such as N2 or Ar. This yields a sintered body (reaction medium with supported radionuclides) in which the radionuclides to be treated are supported on the reaction medium.

[0016] The resulting sintered body is crushed into a powder. The particle size of the powder is preferably between 10 μm and 50 μm.

[0017] The reaction medium is a titanium-containing perovskite oxide. The titanium-containing perovskite oxide is represented by the formula MTiO3 (where M is at least one of Ca, Ba, Sr, Pb, and Mg). The titanium-containing perovskite oxide is supplied in powder form.

[0018] The radionuclides to be treated may be Cs, Ba, Sr, etc. The radionuclides to be treated may be in the form of a powder or liquid compound containing the radionuclides to be treated. The amount of radionuclides to be treated is preferably 1% or more and 5% or less relative to the reaction medium.

[0019] (S2) Hydride substitution A sintered powder containing the radionuclide to be treated is heated together with a hydride donor. This causes some of the oxygen sites of the titanium-containing perovskite oxide to be replaced by hydrogen ions, forming a titanium-containing perovskite oxyhydride (hydride-substituted radionuclide-supported reaction medium) on which the radionuclide to be treated is supported.

[0020] The hydride donor is a hydride powder of an alkali metal or alkaline earth metal selected from lithium hydride (LiH; melting point 680°C), calcium hydride (CaH2; melting point 816°C), strontium hydride (SrH2; melting point 675°C), and barium hydride (BaH2; melting point 675°C).

[0021] The hydride donor is preferably mixed with the powder of the reaction medium supporting the radionuclide to be treated, and heated in contact with it. The hydride donor is mixed with the powder of the sintered body on which the radionuclide to be treated is supported in a weight ratio of 3 to 5 times.

[0022] Heating is carried out in a vacuum or in an inert gas atmosphere. For example, as shown in Figure 2, a sealed container 11 (with an internal vacuum) filled with a mixed powder 10 of the nuclide-supported reaction medium powder and the hydride donor powder sandwiched between quartz wool 23 can be placed in an electric furnace 12 and heated. Instead of creating a vacuum inside, an inert gas atmosphere such as argon (Ar) or nitrogen (N2) may be used. Alternatively, the nuclide-supported reaction medium powder and the hydride donor powder may be separated by the quartz wool 23 and filled into the sealed container 11.

[0023] The heating temperature is 500°C or higher, but below the melting point of the hydride donor. The heating time is 24 hours or longer.

[0024] (S3) Cleaning The packing material (mixed powder 10) after (S2) above is washed with a methanol solution of ammonium chloride (NH4Cl / MeOH solution). After washing, it is rinsed with MeOH. This removes unreacted hydride donors and oxides of components derived from hydride donors. If the powder of the reaction medium carrying the radionuclides to be treated and the powder of the hydride donors are separated, the washing treatment is unnecessary.

[0025] As shown in Figure 3, the radionuclide treatment method according to this embodiment may include, after the washing step (S3), a (S4) deuteride replacement step and a (S5) gas permeation treatment step.

[0026] (S4) Deuterated substitution A titanium-containing perovskite oxyhydride (hydride-substituted reaction medium for supporting the radionuclide to be treated), on which the radionuclide to be treated is supported, is heated in a deuterium gas environment to replace the hydrogen ions in the perovskite oxyhydride with deuterium ions.

[0027] The deuterium gas flow rate is 1 sccm to 10 sccm per gram of titanium-containing perovskite oxyhydride, and heating is performed for 3 to 24 hours at 400°C to 450°C.

[0028] (S5) Gas permeation treatment The reaction medium containing the radionuclide to be treated, after deuteride substitution as described in (S4) above, is heated in a gas environment of hydrogen, deuterium, or tritium.

[0029] Heating can be carried out in a tubular furnace or the like. Figure 4 shows a schematic cross-sectional view of a tubular furnace. After filling the reactor core tube 21 of the tubular furnace 20 with the radionuclide-supported reaction medium (powder) 22 after deuteride substitution, quartz wool 23 is packed into both ends, and while heating with a heater section 24, hydrogen, deuterium, or tritium gas (deuterium D2 in Figure 4) is permeated from one end to the other of the reactor core tube 21.

[0030] Heating in the heater section 24 shall be carried out at 400°C to 450°C for 100 to 200 hours. The gas permeation shall be 1 sccm to 10 sccm per gram of the reaction medium containing the radionuclide to be treated.

[0031] In this radionuclide treatment method, the radionuclide to be treated is mixed with a titanium-containing perovskite oxide and sintered, causing the radionuclide to be supported on the titanium-containing perovskite oxide by a thermal reaction. Figure 5 illustrates the crystal structure of a sintered body obtained by mixing Cs2CO3 with BaTiO3 and sintering it. In the thermal reaction, the radionuclide to be treated (Cs in Figure 5) is distributed on the surface of the titanium-containing perovskite oxide, as shown in Figure 5.

[0032] In this radionuclide treatment method, the amount of radionuclide to be treated can be increased compared to electrodeposition by supporting the radionuclide to the reaction medium on the reaction medium by sintering before hydride substitution. In the titanium-containing perovskite oxyhydride obtained by (S2) hydride substitution and the titanium-containing perovskite oxyhydride after (S4) deuteride substitution, the presence of hydrogen isotopes can promote a reaction in which the radionuclide to be treated is converted to other radionuclides. Therefore, it is possible to treat the radionuclide simply by storing it. Heating the titanium-containing perovskite oxyhydride after (S5) deuteride substitution in a gas environment of hydrogen, deuterium, or tritium can accelerate the treatment of the radionuclide to be treated.

[0033] [Second Embodiment] In this embodiment, the procedure for supporting the radionuclide to be treated differs from the (S1) process for manufacturing the radionuclide-supported reaction medium in the first embodiment. The steps from (S2) hydride substitution onward are the same as in the first embodiment, so their explanation is omitted.

[0034] The reaction medium in this embodiment is the raw material for the titanium-containing perovskite oxide. The titanium-containing perovskite oxide is represented by the formula MTiO3 (where M is at least one of Ca, Ba, Sr, Pb, and Mg). The raw materials for the titanium-containing perovskite oxide are, for example, the carbonate of M and titanium oxide. For example, if the perovskite material containing titanium oxide is BaTiO3, the raw material for the perovskite material containing titanium oxide is a mixed powder of BaCO3 and TiO2.

[0035] The radionuclides to be treated are mixed into the reaction medium and sintered. Sintering is performed by heat treatment at 930°C for 48 hours in an inert gas atmosphere such as N2 or Ar. This yields a sintered body (reaction medium with supported radionuclides) in which the radionuclides to be treated are supported on the reaction medium. The resulting sintered body is then crushed into a powder.

[0036] The radionuclides to be treated may be Cs, Ba, Sr, etc. The radionuclides to be treated may be in powder or liquid form. The amount of radionuclides to be treated may be 1% or more and 5% or less relative to the reaction medium.

[0037] In this radionuclide processing method, the radionuclide to be processed is mixed with a titanium-containing perovskite oxide raw material and sintered, thereby supporting the radionuclide on the titanium-containing perovskite oxide.

[0038] Figure 6 illustrates the crystal structure of a sintered body obtained by mixing BaCO3, TiO2, and Cs2CO3 with a small amount of water and sintering them. When the radionuclide to be treated is mixed with the raw materials for titanium-containing perovskite oxide and sintered, some of the A sites (positions where Ba is present) in the lattice of the titanium-containing perovskite oxide are replaced by the radionuclide to be treated (Cs).

[0039] [Third Embodiment] Figure 7 illustrates a flow chart of a nuclide processing system for implementing the nuclide processing methods of the first and second embodiments described above. The nuclide processing system 30 comprises a sintered body manufacturing unit 31, a hydride replacement unit 32, and a nuclide separation unit 33.

[0040] The sintered body manufacturing unit 31 includes a mixing unit 34 for mixing the radionuclides to be treated with a reaction medium, and a sintering unit 35 for sintering the mixture obtained in the mixing unit 34. The sintered body manufacturing unit 31 may also include a grinding unit (not shown) for grinding the sintered body obtained in the sintering unit 35.

[0041] In the mixing section 34, titanium-containing perovskite oxide or the raw material for titanium-containing perovskite oxide and the radionuclide to be treated may be mixed. Figure 5 illustrates the case where titanium-containing perovskite oxide (BaTiO3) and the radionuclide to be treated (Cs) are mixed. The mixture is heated in the sintering section 35 at a predetermined temperature for a predetermined time to form a sintered body. This yields titanium-containing perovskite oxide on which the radionuclide to be treated is supported.

[0042] The hydride replacement section 32 has a containment section (not shown) for containing the sintered body powder and the hydride donor, and a heating section (not shown) for heating the containment section.

[0043] The hydride replacement section 32 may include a gas supply section 36 capable of supplying hydrogen, deuterium, or tritium to the containment section.

[0044] The containment section is either a sealed container capable of maintaining an internal vacuum or a configuration that maintains the interior in a high-pressure inert gas atmosphere. High pressure refers to a range of 30 MPa to 50 MPa.

[0045] The nuclide separation unit 33 can separate the remaining treated nuclide and newly generated other nuclides (Cs and Pr in Figure 7) from the reaction medium. Separation can be performed using a zeolite separation membrane or the like.

[0046] The separated nuclide to be treated (Cs) is stored in the nuclide storage unit 37 and can be supplied back to the mixing unit 34. Another separated nuclide (Pr) is sent to a waste unit (not shown). The separated reaction medium material (BaTiO3) can be used again in the mixing unit 34.

[0047] The radionuclides to be processed in the first to third embodiments described above may be radioactive. When processed according to the first to third embodiments, for example, the radioactive nuclide Cs is converted to the non-radioactive nuclide Pr. For example, the radioactive nuclide Ba is converted to the non-radioactive nuclide Sm. For example, the radioactive nuclide Sr is converted to the non-radioactive nuclide Mo. The first to third embodiments described above are suitable for the processing and storage of radioactive waste.

[0048] [Example 1] Nuclide treatment was carried out according to the first embodiment.

[0049] Production of reaction media supporting the radionuclide to be treated: 23.3g of BaTiO3, 0.3g of Cs2CO3, and 10mL of water were added to an agate mortar and mixed for about 1 hour. The mixture was placed on a quartz board, and the quartz board was placed in the central part of the alumina furnace tube of a ceramic electric tubular furnace (ARF-50MC, manufactured by Asahi Science & Technology Co., Ltd.). N2 gas was flowed through the alumina furnace tube at a flow rate of 1000 sccm, and the temperature was raised from room temperature to 930°C in 2 hours. After maintaining the temperature at 930°C for 24 hours, the temperature was lowered from 930°C to room temperature, and the quartz board was removed to obtain a sintered body (BaTiO3(Cs)).

[0050] Hydride substitution: The sintered body was placed in an agate mortar and ground, and then the sintered body powder and CaH2 powder were mixed in a weight ratio of 1:5 to obtain a mixed powder.

[0051] One end of a Φ10mm x 200mm quartz tube was sealed with a rounded bottom using a burner, and then the above mixed powder was filled into the quartz tube to a length of 20mm. At this time, quartz wool was packed into both ends of the filled mixed powder. The open end of the quartz tube was connected to a vacuum pump (TVP-215) with a vacuum tube, and the quartz tube was evacuated for 5 minutes. While evacuating, the tube was heated with a burner at a position 120mm from the rounded bottom to perform the sealing process.

[0052] A vacuum-sealed quartz tube was placed in the central part of the alumina furnace tube of a ceramic electric tubular furnace (ARF-50MC, manufactured by Asahi Science & Technology Co., Ltd.). The furnace temperature was raised from room temperature to 550°C in 1 hour and maintained at 550°C for 24 hours. After the temperature was lowered from 550°C to room temperature, the quartz tube was removed, and the central part of the quartz tube was cut with a glass tube cutter, revealing the titanium-containing perovskite oxyhydride (BaTiO) on which the radionuclides to be treated were supported. 3―x H x (Cs)) was extracted.

[0053] Cleaning: BaTiO2 extracted from a quartz tube inside a glove box filled with N2 gas. 3―x H x (Cs) was washed with a 0.1 M NH4Cl / MeOH solution, then rinsed with MeOH to remove unreacted CaH2 and by-product CaO. 3―x H x (Cs) was dried using a suction filter.

[0054] Deuteride replacement and gas permeation treatment: A 400mm long quartz tube with both ends open contains cleaned BaTiO2 in the center. 3―x H x A quartz tube was filled with (Cs) powder (0.8g), and quartz wool was packed into both ends. The quartz tube was then set inside the alumina furnace core of a ceramic electric tubular furnace (ARF-50MC, manufactured by Asahi Rika Seisakusho). Deuterium gas was supplied into the quartz tube at a rate of 1 sccm from one end and exhausted from the other end.

[0055] The furnace temperature was raised from room temperature to 450°C in one hour, and then maintained at 450°C for 124 hours (including 24 hours of deuteride replacement and 100 hours of gas permeation treatment). After that, the temperature was lowered from 450°C to room temperature, the quartz tube was removed, and the treated powder was extracted from inside the quartz tube.

[0056] [Example 2] Preparation of reaction media supporting the radionuclide to be treated, hydride substitution, and washing: The procedure was carried out in the same manner as in Example 1.

[0057] Deuteride substitution and gas permeation treatment: A cleaned BaTiO was filled in the central portion of a quartz tube with a length of 400 mm open at both ends 3―x H x (Cs) powder (0.6 g), and both ends were plugged with quartz wool. Thereafter, deuteride substitution and gas permeation treatment were performed in the same procedure as in Example 1.

[0058] [Comparative Example 1] A powder reagent of BaTiO3 was filled in the central portion of the quartz tube, and deuteride substitution and gas permeation treatment were performed in the same procedure as in Example 1.

[0059] [Comparative Example 2] The powder of the sintered body (BaTiO3(Cs)) of Example 1 was filled in the central portion of the quartz tube without hydride substitution and washing, and deuteride substitution and gas permeation treatment were performed in the same procedure as in Example 1.

[0060] [Comparative Example 3] Production of target nuclide-supporting reaction medium: A sintered body (BaTiO3(Cs)) was obtained in the same procedure as in Example 1.

[0061] Hydride substitution: The sintered body was placed in an agate mortar and pulverized. After one side of a Φ10 mm × 200 mm quartz tube was sealed into a round bottom by burner treatment, 0.2 g of the sintered body powder and 1.0 g of CaH2 powder were filled in the quartz tube over a length of 20 mm without mixing, and both ends were plugged with quartz wool. From this point onward, hydride substitution treatment was performed in the same manner as in Example 1.

[0062] Deuteride substitution and gas permeation treatment: Deuteride substitution and gas permeation treatment were performed in the same procedure as in Example 1.

[0063] [Analysis] The powders after the gas permeation treatment of Examples 1, 2 and Comparative Examples 1 to 3 were dissolved by a dissolution method, and analyzed by inductively coupled plasma mass spectrometry (ICP-MS). The analysis results are shown in Table 1.

[0064] [Table 1]

[0065] In the reaction medium 133 Comparative Example 1, in which Cs was not supported 133 The Cs content was 0.3 ppm. On the other hand, in Example 1 133 Cs was 34.3 ppm in Example 2. 133 The Cs content was 44.1. This result confirmed that the radionuclide to be treated could be supported on the reaction medium by the solid-phase method, which involves mixing the radionuclide to be treated with titanium-containing perovskite oxide (BaTiO3) and sintering it.

[0066] 133 Comparative Example 2, in which Cs was supported but hydride substitution was not performed. 133 The Cs content was 575.4 ppm, which is higher than in Examples 1 and 2. 133 The Cs concentration was high. This is due to hydride substitution. 133 Cs vaporized and was absorbed into the CaH2 side, or by washing after hydride substitution. 133 This is thought to be the result of a Cs leak.

[0067] Comparative Example 3, in which the hydride donor was heated (hydride treatment) without being mixed with titanium-containing perovskite oxide (BaTiO3) 133 The Cs content was 273.3 ppm, which was lower than in Comparative Example 2. This is because, when CaH2 is not mixed, removal of unreacted CaH2 after hydride substitution is unnecessary, and therefore the washing treatment was not performed. Compared to Comparative Example 2, factors other than the washing treatment were observed. 133 It can be seen that the Cs content is off by about 300 ppm. Also, from the comparison between Comparative Example 3 and Example 1, it can be seen that the washing treatment 133 It can be seen that the Cs level is off by about 230 ppm. In other words, it was able to be supported during the hydride substitution treatment. 133 The amount of Cs can be estimated to be equivalent to that in Comparative Example 3. Pr may also have been removed during washing, but this could not be confirmed due to the small amount. In Examples 1 and 2, the powder changed from white to black before and after hydride treatment. This discoloration is due to the substitution of oxygen ions in BaTiO3 with hydrogen ions. On the other hand, the powder of Comparative Example 3 only changed to light gray after hydride treatment. This suggests that the effect of insufficient hydride substitution is significant. 141 It can be inferred that Pr was not detected.

[0068] In both Examples 1 and 2, 141 The Pr concentration was approximately 20 ppb. The value of 20 ppb is the same as that of Comparative Examples 1-3. 141 Because it is clearly higher than the Pr concentration, Examples 1 and 2 141 It is clear that the Pr value does not indicate contamination. This suggests that new nuclides are generated by processing the radionuclides according to the first embodiment.

[0069] 141 Pr is, 133 It is hypothesized that this occurs when four D atoms, each containing two protons, fuse with Cs, but the details are not yet clear. According to Table 1 (Pr / Cs), the reaction medium is supported by... 133 Approximately 0.05% of Cs 141 Converted to Pr.

[0070] [Example 3] Nuclide treatment was carried out according to the second embodiment.

[0071] Production of reaction media supporting the radionuclide to be treated: 17.7g of BaCO3, 7.9g of TiO2, 1.6g of Cs2CO3, and 20cc of pure water were added to an agate mortar and mixed for about 1 hour. The mixture was placed on a quartz board, and the quartz board was placed in the central part of the alumina furnace tube of a ceramic electric tubular furnace (ARF-50MC, manufactured by Asahi Rika Seisakusho). N2 gas was flowed through the alumina furnace tube at a flow rate of 1000 sccm, and the temperature was raised from room temperature to 930°C in 2 hours. After maintaining the temperature at 930°C for 24 hours, the temperature was lowered from 930°C to room temperature, and the quartz board was removed and the sintered body (Ba x Cs 1-x TiO3 was obtained.

[0072] Hydride substitution: The sintered body was placed in an agate mortar and ground, and then the sintered body powder and CaH2 powder were mixed in a weight ratio of 1:5 to obtain a mixed powder.

[0073] One end of a Φ10mm x 200mm quartz tube was sealed with a rounded bottom using a burner, and then the above mixed powder was filled into the quartz tube to a length of 20mm. At this time, quartz wool was packed into both ends of the material. The open end of the quartz tube was connected to a vacuum pump (TVP-215) with a vacuum tube, and the quartz tube was evacuated for 5 minutes. While evacuating, the tube was heated with a burner at a position 120mm from the rounded bottom to perform the sealing process.

[0074] A vacuum-sealed quartz tube was placed in the central part of the alumina furnace tube of a ceramic electric tubular furnace (ARF-50MC, manufactured by Asahi Rika Seisakusho). The furnace temperature was raised from room temperature to 550°C in 1 hour and maintained at 550°C for 170 hours. After the temperature was lowered from 550°C to room temperature, the quartz tube was removed, and the central part of the quartz tube was cut with a glass tube cutter, and the titanium-containing perovskite oxyhydride (Ba), on which the radionuclides to be treated were supported, was extracted from the inside. x Cs 1-x TiO 3―x H x ) was taken out.

[0075] Cleaning: Ba extracted from a quartz tube inside a glove box filled with N2 gas x Cs 1-x TiO 3―x H x The sample was washed with a 0.1 M NH4Cl / MeOH solution, then rinsed with MeOH to remove unreacted CaH2 and by-product CaO. x Cs 1-x TiO 3―x H x It was dried using a suction filter.

[0076] Deuteride replacement and gas permeation treatment: The procedure was carried out in the same manner as in Example 1.

[0077] [Example 4] During hydride substitution, the holding time at 550°C was set to 504 hours. The rest of the procedure was the same as in Example 3.

[0078] [Comparative Example 4] Figure 8 shows a schematic diagram of the electrodeposition apparatus used in the manufacture of Comparative Example 4. The BaTiO3 powder reagent was subjected to hydride substitution, washing, and deuteride substitution using the same procedure as in Example 1. 3―X―Y (H X ,D Y A solution of 0.02 N CsNO2 dissolved in light water or heavy water was placed in a titanium container (negative electrode). 3―X―Y (H X ,D Y After the powder settled at the bottom of the container, a 1 μm filter, PTFE mesh, and zirconia oxide balls were placed on top to suppress diffusion in the liquid. A Pt electrode (positive electrode) was placed at the top of the solution, and a voltage of 1 V was applied between it and a titanium container (negative electrode) for 4 hours to electrodeposit Cs.

[0079] Gas permeation treatment: After washing with pure water and drying at 80°C for 1 hour, gas permeation treatment was performed using the same procedure as in Example 1.

[0080] [Comparative Example 5] Cs was electrodeposited by applying a voltage of 6V between the Pt electrode (positive electrode) and the titanium container (negative electrode) for 14 hours using the same procedure as in Comparative Example 4.

[0081] Gas permeation treatment: After washing with pure water and drying at 80°C for 1 hour, gas permeation treatment was performed using the same procedure as in Example 1.

[0082] 〔analysis〕 The powders from Examples 3 and 4 and Comparative Examples 4 and 5, after gas permeation treatment, were dissolved by a dissolution method and analyzed by inductively coupled plasma mass spectrometry (ICP-MS). The analysis results are shown in Table 2.

[0083] [Table 2]

[0084] Examples 3 and 4, in which Cs2CO3 was mixed with the raw material for titanium-containing perovskite oxide and sintered, had more Cs supported than Comparative Examples 4 and 5 (electrodeposition).

[0085] In Examples 3 and 4, 141 The Pr concentrations were 2.6 ppb and 2.7 ppb. (Blank) 141 Since the Pr concentration is 0.27 ppb, in Examples 3 and 4, which were treated with radionuclides according to the second embodiment, 141 It can be said that a new Pr has been generated.

[0086] According to Table 2 (Pr / Cs), in Examples 3 and 4, the reaction medium was supported. 133 Approximately 0.00015% of Cs 141 It had been converted to Pr.

[0087] <Note> The nuclide processing method and nuclide processing system described in the embodiments above can be understood, for example, as follows.

[0088] A radionuclide treatment method according to a first aspect of this disclosure involves (S1) supporting the radionuclide to be treated on a titanium-containing perovskite oxide by sintering, and (S2) heating the titanium-containing perovskite oxide on which the radionuclide to be treated is supported together with a hydride donor in a vacuum or in an inert gas atmosphere to replace some of the oxygen sites of the titanium-containing perovskite oxide with hydrogen ions to form a titanium-containing perovskite oxyhydride on which the radionuclide to be treated is supported.

[0089] By supporting the radionuclides to be treated on titanium-containing perovskite oxide through sintering, the amount of radionuclides supported can be increased compared to when they are supported by electrodeposition.

[0090] As the amount of radionuclides to be treated increases, a process may occur in which some of the oxygen sites of titanium-containing perovskite oxides are replaced by hydrogen ions (hydride substitution), or during storage of titanium-containing perovskite hydrides in the presence of hydrogen ions, the radionuclides to be treated are converted to other radionuclides, potentially reducing the amount of radionuclides to be treated.

[0091] According to the first aspect of this disclosure, radionuclides can be processed using a simple procedure. According to the first aspect of this disclosure, storage and management of radionuclides become easier even if they are radioactive.

[0092] A radionuclide treatment method according to a second aspect of this disclosure involves, in the first aspect described above, mixing the radionuclide to be treated with the titanium-containing perovskite oxide and sintering the mixture to support the radionuclide on the titanium-containing perovskite oxide.

[0093] In a sintered body produced by mixing a radionuclide to be treated with titanium-containing perovskite oxide and sintering it, the radionuclide to be treated is distributed on the surface of the titanium-containing perovskite oxide due to thermal reactions. Radionuclides distributed on the surface are more susceptible to conversion reactions into other radionuclides.

[0094] A third aspect of the present disclosure relates to a radionuclide treatment method in the first aspect described above, in which the radionuclide to be treated is mixed with the raw material for the titanium-containing perovskite oxide and sintered to support the radionuclide to be treated on the titanium-containing perovskite oxide.

[0095] In a sintered body produced by mixing the radionuclide to be treated with a titanium-containing perovskite oxide raw material and sintering it, the radionuclide to be treated is substituted at the A-site of the perovskite structure. This procedure (A-site substitution method) allows for the support of a larger number of radionuclides to be treated on the titanium-containing perovskite oxide, which is the reaction medium, compared to the solid-phase method in which the radionuclide to be treated is mixed with the titanium-containing perovskite oxide and sintered.

[0096] In the fourth aspect of this disclosure, the radionuclide processing method is carried out in any of the first to third aspects described above, wherein the heating is performed in a gas environment of hydrogen, deuterium, or tritium.

[0097] The nuclide treatment method according to the fifth aspect of this disclosure involves heating (S4, S5) a titanium-containing perovskite oxyhydride on which the nuclide to be treated is supported, in any of the first to third aspects described above, under a gas environment of hydrogen, deuterium, or tritium.

[0098] Heating in the presence of hydrogen, deuterium, or tritium can accelerate reactions that convert the treated nuclide into another nuclide.

[0099] A nuclide processing system according to a sixth aspect of the present disclosure comprises a sintered body manufacturing unit (31) for manufacturing a sintered body in which a nuclide to be processed is supported on a titanium-containing perovskite oxide, and a hydride substitution unit (32) for containing a mixture of the sintered body and a hydride donor, and heating the mixture to perform hydride substitution.

[0100] In the nuclide processing system according to the seventh aspect of this disclosure, in the sixth aspect described above, the sintered body manufacturing section comprises a mixing section (34) for mixing the nuclide to be processed with the titanium-containing perovskite oxide or the raw material for the titanium-containing perovskite oxide, and a sintering section (35) for sintering the mixture obtained in the mixing section.

[0101] In the nuclide processing system according to the eighth aspect of this disclosure, in the sixth or seventh aspect, the hydride substitution unit includes a gas supply unit (36) that supplies hydrogen, deuterium, or tritium gas to the mixture. [Explanation of symbols]

[0102] 10 Mixed powder (of titanium-containing perovskite oxide and hydride donor on which the radionuclide to be treated is supported) 11. Airtight container 12 Electric furnace 20 tube furnace 21 Core tubes 22. Deuteride-substituted reaction medium for supporting radionuclides to be treated. 23 Quartz wool 24 Heater section 30 radionuclide processing systems 31. Sintered Body Manufacturing Department 32 Hydride substitution section 33. Nuclide separation section 34 Mixing section 35 Sintered part 36 Gas Supply Department 37 Storage section for radionuclides to be treated

Claims

1. By sintering, the radionuclide to be treated is supported on a titanium-containing perovskite oxide. A radionuclide treatment method comprising heating a titanium-containing perovskite oxide on which the radionuclide to be treated is supported together with a hydride donor in a vacuum or in an inert gas atmosphere, thereby replacing some of the oxygen sites of the titanium-containing perovskite oxide with hydrogen ions to form a titanium-containing perovskite oxyhydride on which the radionuclide to be treated is supported.

2. The radionuclide treatment method according to claim 1, comprising mixing the radionuclide to be treated with the titanium-containing perovskite oxide and sintering the mixture to support the radionuclide on the titanium-containing perovskite oxide.

3. The radionuclide treatment method according to claim 1, comprising mixing the radionuclide to be treated with the raw material of the titanium-containing perovskite oxide, sintering the mixture, and supporting the radionuclide to be treated on the titanium-containing perovskite oxide.

4. The radionuclide treatment method according to claim 1, wherein the heating is carried out in a gas environment of hydrogen, deuterium, or tritium.

5. The radionuclide treatment method according to claim 1, wherein the titanium-containing perovskite oxyhydride on which the radionuclide to be treated is supported is heated in a gas environment of hydrogen, deuterium, or tritium.

6. A sintered body manufacturing unit that manufactures sintered bodies in which the radionuclides to be treated are supported on titanium-containing perovskite oxide, A radionuclide processing system comprising: a hydride substitution unit that contains a mixture of the sintered body and a hydride donor, and heats the mixture to replace the hydride.

7. The nuclide processing system according to claim 6, wherein the sintered body manufacturing section comprises a mixing section for mixing the nuclide to be processed with the titanium-containing perovskite oxide or the raw material for the titanium-containing perovskite oxide, and a sintering section for sintering the mixture obtained in the mixing section.

8. The radionuclide processing system according to claim 6, wherein the hydride substitution unit comprises a gas supply unit that supplies hydrogen, deuterium, or tritium to the mixture.

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