JP2015190786A - nuclide conversion system and nuclide conversion method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nuclide conversion system and a nuclide conversion method capable of increasing a nuclide conversion amount.SOLUTION: A nuclide conversion system 1 comprises: a reaction device 10 including a structure 13 through which heavy hydrogen can pass, a storage part 11, a heavy hydrogen low density part 12 and an electrode 14; an electro-deposition liquid supply part 50; an electrolyte solution supply part 60; and a power source 15. The electro-deposition liquid including a material which is subjected to nuclide conversion and a hydrogen storage metal, is supplied to the storage part 11, and an electro-deposition layer including the hydrogen storage metal and the material which is subjected to nuclide conversion, is formed on a surface of the structure 13 by an electrolytic method. Then, a heavy solution including an electrolyte is supplied to the storage part 11, and voltage is applied to the electrode 14 for generating heavy hydrogen. When the heavy hydrogen passes through the structure 13 by difference of heavy hydrogen density between the storage part 11 and the heavy hydrogen low density part 12, the material which is subjected to nuclide conversion in the electro-deposition layer is converted into other element.

Description

  The present invention relates to a radionuclide conversion system and a nuclide conversion method according to a radioactive waste treatment technique, a technique for generating a rare element from elements abundant in nature, and the like.

  Patent Documents 1 to 3 disclose nuclide conversion apparatuses capable of performing nuclide conversion with a relatively small apparatus as compared with a large apparatus such as an accelerator or a nuclear reactor.

  In the nuclide conversion device disclosed in the above-mentioned document, a substance to be subjected to nuclide conversion is added to one surface of a structure containing a hydrogen storage metal such as palladium (Pd) or a palladium alloy or a hydrogen storage alloy. When deuterium permeates the structure, a nuclide conversion reaction occurs in which a substance subjected to nuclide conversion is converted to another nuclide.

  In patent document 1, electrolysis, vapor deposition, and sputtering are mentioned as a method of adding the substance subjected to nuclide conversion to the structure. Further, Patent Document 4 discloses that a substance that undergoes nuclide conversion is added to the structure using an ion implantation method.

Japanese Patent No. 4346838 Japanese Patent No. 4347261 Japanese Patent No. 4347262 JP 2012-93303 A

  In the methods described in Patent Documents 1 to 3, since the addition region is limited to the surface of the structure, it is difficult to add a substance that is subjected to a large amount of nuclide conversion at a time. In the ion implantation method described in Patent Document 4, an element is implanted into the structure with a high acceleration voltage, which may destroy the structure of the structure.

  In order to perform vapor deposition, sputtering, and ion implantation, a vacuum chamber and a vacuum pump are required. In the ion implantation, an ion source for ionizing the implanted element and a power source for accelerating the ions with a high voltage are required. In these methods, a large-scale apparatus is required for the addition of the substance subjected to the nuclide conversion, and the cost required for the addition process is increased. In addition, the size of the substrate that can be processed by vapor deposition, sputtering, and ion implantation is limited. That is, these methods are not suitable for increasing the area of structures and mass production.

  When an accident occurs at a nuclear power plant, a large amount of radioactive material is released into the environment. Nuclide conversion technology is useful for converting radioactive materials into stable nuclides and detoxifying them. In order to apply to the processing of radioactive material, it is necessary to increase the amount of radioactive material (material subjected to nuclide conversion) added to the structure. Moreover, when processing a radioactive substance, it is desired to set it as the apparatus from which an operator is not exposed to a high radiation environment.

  The present invention has been made in view of the above problems, and an object thereof is to provide a nuclide conversion system and a nuclide conversion method capable of increasing the amount of nuclide conversion.

  According to a first aspect of the present invention, a deuterium-permeable structure, a reservoir and a deuterium low-concentration portion that are closed by the structure, and the reservoir are accommodated in the reservoir. An electrodeposition liquid supply unit that supplies an electrodeposition liquid containing at least one reaction device, a substance subjected to nuclide conversion, and a hydrogen storage metal, to the storage unit An electrolyte solution supply unit that supplies a heavy aqueous solution containing an electrolyte to the storage unit, a discharge unit that discharges the electrodeposition liquid and the heavy aqueous solution containing the electrolyte from the storage unit, and a power source connected to the electrode, Is a nuclide conversion system.

  According to a second aspect of the present invention, a deuterium-permeable structure, a reservoir and a deuterium low-concentration portion that are closed by the structure, and the reservoir are accommodated in the reservoir. A nuclide conversion method using a nuclide conversion system having at least one reaction device including an electrode disposed opposite to a surface on the part side, wherein the nuclide conversion method includes a substance to be subjected to nuclide conversion and a hydrogen storage metal. An electrodeposition liquid supply step for supplying the liquid deposit to the storage portion and immersing the structure in the electrodeposition liquid; and a surface facing the surface of the structure on the storage portion side after the electrodeposition liquid supply step A current of a predetermined value is passed through the electrode to generate a voltage difference between the electrode and the structure, and the hydrogen storage metal and the nuclide conversion are performed on the surface of the structure on the storage portion side. An electrodeposition layer forming step of forming an electrodeposition layer containing a substance to be formed; An electrodeposition liquid discharging step of discharging the electrodeposition liquid from the reservoir after forming the layer; and after the electrodeposition liquid is discharged, supplying a heavy aqueous solution containing an electrolyte to the reservoir, A deuterium solution supplying step of immersing the structure in a deuterated aqueous solution containing, a deconcentration step of maintaining the deuterium concentration portion in a low state, and applying a predetermined voltage to the electrode, The deuterium is generated from the deuterated aqueous solution in the space between the electrode and the structure, and the deuterium permeates the structure so that the nuclide conversion substance in the electrodeposition layer is provided. After the nuclide conversion step to be nuclide-converted and the nuclide conversion step is completed, a voltage difference opposite to that of the electrodeposition layer forming step is generated between the electrode and the structure, and the electrodeposition layer is Nuclide change including electrodeposition layer peeling process for peeling from structure It is a method.

  In the first aspect, the structure includes a substrate made of the hydrogen storage metal or a hydrogen storage alloy, a first layer made of the hydrogen storage metal or the hydrogen storage alloy on the substrate, the hydrogen storage metal or the hydrogen storage metal. Second layers made of a material having a relatively low work function with respect to the hydrogen storage alloy are alternately stacked, and the substrate is directed to the deuterium low concentration portion side, and the surface opposite to the substrate In addition, an electrodeposition layer including the material subjected to the nuclide conversion and the hydrogen storage metal is formed.

  2nd aspect WHEREIN: The said structure is a board | substrate which consists of the said hydrogen storage metal or a hydrogen storage alloy, The 1st layer which consists of the said hydrogen storage metal or the said hydrogen storage alloy on the said board | substrate, The said hydrogen storage metal or the said It is preferable that second layers made of a material having a relatively low work function with respect to the hydrogen storage alloy are alternately stacked, and the electrodeposition layer is formed on the surface opposite to the substrate.

  In the first aspect, a depressurizing device that depressurizes the inside of the deuterium low concentration portion or an inert gas supply device that supplies an inert gas to the deuterium low concentration portion is connected to the deuterium low concentration portion. It is preferred that

  2nd aspect WHEREIN: It is preferable that the said low concentration process is a process of decompressing the inside of the said deuterium low concentration part, or a process of supplying an inert gas in the said deuterium low concentration part.

  In the present invention, formation of an electrodeposition layer (attachment of a substance subjected to nuclide conversion) to the structure, nuclide change treatment, and peeling of the electrodeposition layer can be repeatedly performed in the same apparatus. This eliminates the need for a separate device for attaching the substance subjected to nuclide conversion, simplifies the processing, and improves the operating efficiency of the system. In the present invention, the frequency of removing the structure from the system is greatly reduced. If the material subjected to nuclide conversion is radioactive, the frequency of exposure of the material subjected to nuclide conversion to the outside of the device will be greatly reduced, which will increase the safety of workers. Can do.

  If the material to be subjected to nuclide conversion and the hydrogen storage metal or hydrogen storage alloy are simultaneously electrodeposited, the material to be subjected to the nuclide conversion will be taken into the electrodeposited layer and adhere to the structure per unit area The amount of material to be converted is increased. Further, the amount of the substance subjected to nuclide conversion is substantially uniform in the film thickness direction. Further, the electrodeposition method can be electrodeposited on a substrate having a large area as compared with vapor deposition, ion implantation or the like. Therefore, compared to the case where a substance that can be subjected to nuclide conversion is added only to the structure surface, the present invention increases the amount of the substance that can be subjected to nuclide conversion into one structure, thus increasing the amount of nuclide conversion. To do.

  1st aspect WHEREIN: When the said electrodeposition liquid is accommodated in the said storage part, it is preferable that the said power supply applies the electric current of a predetermined | prescribed current density to the said electrode.

In a second aspect, the material is subjected to the nuclide is the base metal, the hydrogen storage metal is a noble metal, in the electrodeposited layer forming step, 0.11mA / cm ² or more 10 mA / cm ² or less of the current It is preferable that a current be applied to the electrode so as to obtain a density.

  In the second aspect, the material subjected to the nuclide conversion is a base metal, the hydrogen storage metal is a noble metal, and the deposition rate of the electrodeposition layer in the electrodeposition layer forming step is 0.05 nm / min. It is preferably 100 nm / min or less

  When the material subjected to nuclide conversion is a base metal and the hydrogen storage metal is a noble metal, the material subjected to nuclide conversion is easily ionized under the condition that an electrodeposition layer of the hydrogen storage metal is formed. The inventors of the present invention have focused on the fact that by forming an electrodeposition layer at a lower current density (film formation rate), the number of substances subjected to nuclide conversion incorporated into the electrodeposition layer increases. If it is the said conditions, since the addition amount of the substance to which a nuclide conversion is performed increases significantly compared with the conventional method made to adhere only to the surface of a structure, it is advantageous.

  In the first aspect, it is preferable that a cleaning liquid supply unit that supplies a cleaning liquid to the storage unit is further provided, and the cleaning liquid after cleaning is discharged from the discharge unit.

  2nd aspect WHEREIN: It is preferable to further include the washing | cleaning process which supplies a washing | cleaning liquid to the said storage part and wash | cleans the said storage part between the said electrodeposition liquid discharge process and the said heavy aqueous solution supply process.

  If the electrodeposition liquid remains in the reservoir, the components of the electrodeposition liquid may become contaminated and inhibit the nuclide conversion reaction. If washing is performed between the electrodeposition and the nuclide conversion treatment, the influence of contamination can be reduced.

If the nuclide conversion system and the nuclide conversion method of the present invention are used, it is possible to add a substance subjected to a large amount of nuclide conversion to the structure, and the amount of nuclide conversion per unit area of the structure increases.
In the present invention, the electrodeposition and the nuclide conversion reaction can be repeated in the same apparatus without taking out the structure. For this reason, work efficiency is improved, and when the material subjected to nuclide conversion has radioactivity, it is possible to suppress the exposure of workers.

1 is a schematic diagram of a nuclide conversion system according to a first embodiment. It is a section schematic diagram of an example of a structure. It is a graph which shows the relationship between Cs / Pd atomic number ratio and the amount of Cs adhesion. It is a graph which shows the relationship between the current density provided to an electrode, and the amount of Cs adhesion. It is a graph which shows the relationship between film forming speed and the amount of Cs adhesion. It is an experimental result of nuclide conversion reaction. It is the schematic of the nuclide conversion system which concerns on 2nd Embodiment. It is the schematic of the nuclide conversion system which concerns on 3rd Embodiment.

<First Embodiment>
FIG. 1 is a schematic diagram of a nuclide conversion system according to the first embodiment of the present invention. The nuclide conversion system 1 includes a reaction apparatus 10, an electrodeposition liquid supply unit 50, and an electrolyte solution supply unit 60.
The reaction apparatus 10 includes a storage unit 11 and a deuterium low concentration unit 12. The storage part 11 and the deuterium low concentration part 12 are separated by the structure 13, and each constitutes a closed space.

  The structure 13 includes a hydrogen storage metal or a hydrogen storage alloy. The hydrogen storage metal is palladium (Pd), nickel (Ni), or the like. Examples of the hydrogen storage alloy include a palladium alloy and a nickel alloy.

FIG. 2 is a schematic cross-sectional view of an example of the structure 13. The structure 13 of FIG. 2 includes a layer (first layer) 22 of a hydrogen storage metal or a hydrogen storage alloy (for example, Pd) on a substrate 21 (for example, a Pd substrate) made of a bulk hydrogen storage metal or a hydrogen storage alloy, A laminate in which layers (second layers) 23 of substances having a work function relatively lower than that of the hydrogen storage metal or hydrogen storage alloy (work function is 3 eV, for example, CaO, TiC, Y ₂ O ₃ ) 23 are alternately stacked. 24 is formed. In FIG. 2, a total of 10 first layers 22 and second layers 23 are laminated, and the outermost layer is the first layer 22. The structure 13 is arranged so that the stacked body 24 faces the storage unit 11 side (that is, the substrate 21 side faces the deuterium low concentration unit side). The first layer 22 and the second layer 23 are formed by using, for example, an argon ion beam sputtering method.

  The reaction apparatus 10 further includes an electrode 14 in the storage unit 11. The electrode 14 is a plate-like electrode manufactured from platinum (Pt) or the like. The electrode 14 is disposed opposite to the surface of the structure 13 on the side of the laminate 24. The electrode 14 and the structure 13 are connected to a power source 15 disposed outside the reaction apparatus 10.

  A check valve 16 is installed in the storage unit 11 of the reaction apparatus 10. The check valve 16 is provided in a flow path that connects the storage unit 11 and the external atmosphere. The check valve 16 is closed when the atmospheric pressure of the external atmosphere is larger than the atmospheric pressure of the gas stored in the storage unit 11. The check valve 16 is opened when the pressure of the gas stored in the storage unit 11 is larger than the pressure of the external atmosphere, and exhausts the gas in the storage unit 11 to the external atmosphere.

  A deconcentration means is connected to the deuterium low concentration portion 12. In the nuclide conversion system 1 of FIG. 1, a decompression device 17 is installed as a concentration reducing means. The decompression device 17 includes a vacuum pump 18 and an exhaust pipe 19. The vacuum pump is, for example, a turbo molecular pump or a dry pump. The decompression device 17 discharges the gas inside the deuterium low concentration part 12 to reduce the pressure in the deuterium low concentration part 12.

Instead of the decompression device 17, an inert gas supply device may be installed in the deuterium low concentration unit 12. The inert gas supply unit includes a gas source, an inert gas supply pipe, and an exhaust pipe. The inert gas supply unit supplies an inert gas (for example, N ₂ , Ar) to the deuterium low concentration unit 12. Since the inside of the deuterium low concentration portion 12 is maintained at a predetermined pressure, the gas in the deuterium low concentration portion 12 is discharged through the exhaust pipe.

  A heater 20 is installed in the vicinity of the structure 13 in the deuterium low concentration portion 12. The heater 20 heats the deuterium low concentration portion 12 side of the structure 13 to a predetermined temperature.

  The nuclide conversion system 1 in FIG. 1 includes a circulation unit 30. The circulation unit 30 includes an extraction pipe 31, a heat exchanger 32, a filter 33, a pump 34, a resupply pipe 35, and a valve V <b> 1 installed in the resupply pipe 35. The heat exchanger 32 cools the liquid supplied from the extraction pipe 31. The filter 33 removes impurities by filtering the liquid supplied from the extraction pipe 31. The pump 34 supplies the liquid filtered by the filter 33 to the storage unit 11 via the resupply pipe 35.

  In the nuclide conversion system 1 of FIG. 1, the discharge unit 40 is connected to the upstream side of the valve V <b> 1 of the resupply pipe 35. The discharge unit 40 includes a discharge pipe 41 and a valve V2. The discharge unit 40 discharges the liquid extracted from the storage unit 11 to the outside of the system. The discharge unit 40 may be directly connected to the storage unit 11.

  The electrodeposition liquid supply unit 50 is connected to the storage unit 11. In the configuration of FIG. 1, the electrodeposition liquid supply unit 50 is connected to the resupply pipe 35 of the circulation unit 30, but may be directly connected to the storage unit 11 of the reaction apparatus 10.

  The electrodeposition liquid supply unit 50 includes an electrodeposition liquid tank 51, an electrodeposition liquid supply pipe 52, an inert gas supply pipe 53, a dehumidifier 54, and a dry inert gas supply pipe 55.

The inert gas supply pipe 53 forms a flow path that connects a gas source (not shown) and the dehumidifier 54. The inert gas supply pipe 53 supplies an inert gas having a predetermined flow rate of an inert gas (CE (Cold Evaporator) _N _{2 in} FIG. 1) supplied from a gas source to the dehumidifier 54. Ar gas or the like is also applicable as the inert gas.

  The dehumidifying device 54 includes a filter with a dehumidifying function exemplified by silica gel. The dehumidifier 54 removes impurities from the inert gas supplied from the inert gas supply pipe 53 and dries the inert gas.

  The dry inert gas supply pipe 55 forms a flow path connecting the dehumidifier 54 and the electrodeposition liquid tank 51. The dry inert gas supply pipe 55 supplies an inert gas having a predetermined flow rate among the inert gases dried by the dehumidifying device 54 to the electrodeposition liquid tank 51 by being controlled by the control device.

The electrodeposition liquid tank 51 constitutes a closed space in which the electrodeposition liquid is stored. The electrodeposition solution contains a salt of a hydrogen storage metal, such as a Pd salt. The electrodeposition liquid further contains a substance to be subjected to nuclide conversion. The substances subjected to nuclide conversion are specifically Cs, Sr, Na, and Ba. A salt of a substance to be subjected to nuclide conversion may be added to the electrodeposition solution. Or the radioactive substance discharged | emitted from nuclear power plants, such as ¹³⁷ Cs, may be added to the electrodeposition liquid.

  The heater 56 is disposed around the outside of the electrodeposition liquid tank 51. The heater 56 controls the electrodeposition liquid in the electrodeposition liquid tank 51 to a predetermined temperature.

In the configuration of FIG. 1, the electrodeposition liquid supply pipe 52 forms a flow path connecting the electrodeposition liquid tank 51 and the resupply pipe 35.
By supplying the inert gas from the dry inert gas supply pipe 55 to the electrodeposition liquid tank 51, the inside of the electrodeposition liquid tank 51 is pressurized. Thereby, the electrodeposition liquid is fed to the storage unit 11 of the reaction apparatus 10 through the electrodeposition liquid supply pipe 52. The supply amount of the electrodeposition liquid is controlled by a valve V3 installed in the electrodeposition liquid supply pipe 52.

  The electrolyte solution supply unit 60 includes an electrolyte solution tank 61, an electrolyte solution supply pipe 62, a heavy water supply unit 65, and an inert gas supply unit 71.

  The heavy water supply unit 65 includes an inert gas supply pipe 66, a dehumidifier 67, a dry inert gas supply pipe 68, a heavy water tank 69, and a heavy water supply pipe 70.

The inert gas supply pipe 66 forms a flow path that connects a gas source (not shown) and the dehumidifier 67. The dry inert gas supply pipe 68 forms a flow path connecting the dehumidifier 67 and the heavy water tank 69.
The heavy water tank 69 constitutes a closed space in which heavy water (D ₂ O) is stored. The heavy water supply pipe 70 forms a flow path connecting the heavy water tank 69 and the electrolyte solution tank 61.

  Similar to the electrodeposition liquid supply unit 50, an inert gas supplied from a gas source (not shown) passes through an inert gas supply pipe 66, a dehumidifier 67, and a dry inert gas supply pipe 68 to generate heavy water. It is supplied to the tank 69. As a result, the inside of the heavy water tank 69 is pressurized, and heavy water is supplied to the electrolyte solution tank 61 through the heavy water supply pipe 70. The supply amount of heavy water is controlled by a valve V5 installed in the heavy water supply pipe 70.

The inert gas supply unit 71 includes an inert gas supply pipe 72, a dehumidifier 73, and a dry inert gas supply pipe 74.
The inert gas supply pipe 72 forms a flow path that connects a gas source (not shown) and the dehumidifier 73. The dry inert gas supply pipe 74 forms a flow path that connects the dehumidifier 73 and the electrolyte solution tank 61.

  Similarly to the electrodeposition liquid supply unit 50, the inert gas supply unit 71 supplies nitrogen gas supplied from a gas source (not shown) to the electrolyte solution tank 61. By supplying nitrogen gas from the dry inert gas supply pipe 74 to the electrolyte solution tank 61, the inside of the electrolyte solution tank 61 is pressurized.

The electrolyte solution tank 61 constitutes a closed space in which the electrolyte solution is stored. An electrolyte salt 63 is disposed at the bottom of the electrolyte solution tank 61. The type of the electrolyte salt 63 is not particularly limited, but is preferably a salt of the same element as a substance subjected to nuclide conversion described later. For example, cesium nitrate CsNO ₃ , cesium hydroxide CsOH, sodium nitrate NaNO ₃ , and strontium nitrate Sr (NO ₃ ) ₂ . The solvent of the electrolyte solution is heavy water. The electrolyte salt 63 dissolves when immersed in heavy water, and an electrolyte solution is generated.

  The heater 64 is disposed around the outside of the electrolyte solution tank 61. The heater 64 controls the electrolyte solution in the electrolyte solution tank 61 to a predetermined temperature. By controlling the temperature of the electrolyte solution and the amount of heavy water supplied from the heavy water supply unit 65, the electrolyte concentration in the electrolyte solution is adjusted. In this embodiment, the electrolyte concentration is between 0.001 mol / l and a saturated concentration.

  The electrolyte solution supply pipe 62 forms a flow path that connects the electrolyte solution tank 61 and the storage unit 11 of the reaction apparatus 10. When the inside of the electrolyte solution tank 61 is pressurized, the electrolyte solution tank 61 is fed to the storage unit 11 through the electrolyte solution supply pipe 62. The supply amount of the electrolyte solution is controlled by a valve V4 installed in the electrolyte solution supply pipe 62.

In the nuclide conversion system 1 of FIG. 1, a heavy water replenishment unit 80 is connected to the storage unit 11. The heavy water replenishment unit 80 includes an inert gas supply pipe 81, a dehumidifier 82, a dry inert gas supply pipe 83, a heavy water tank 84, and a heavy water replenishment pipe 85.
The inert gas supply pipe 81 forms a flow path for connecting a gas source (not shown) and the dehumidifier 82. The dry inert gas supply pipe 83 forms a flow path connecting the dehumidifier 82 and the heavy water tank 84. The heavy water supply pipe 85 forms a flow path connecting the heavy water tank 84 and the storage unit 11. The heavy water tank 84 constitutes a closed space in which heavy water (D ₂ O) is stored.

  Similar to the electrodeposition liquid supply unit 50 and the electrolyte solution supply unit 60, nitrogen gas supplied from a gas source (not shown) passes through an inert gas supply pipe 81, a dehumidifier 82, and a dry inert gas supply pipe 83. Via, it is supplied to the heavy water tank 84 and the inside of the heavy water tank 84 is pressurized. When the inside of the heavy water tank 84 is pressurized, heavy water is supplied to the storage unit 11 through the heavy water replenishment pipe 85. The supply amount of heavy water is controlled by a valve V6 installed in the heavy water replenishment pipe 85.

  The nuclide conversion system 1 may further include a cleaning liquid supply unit 90. In FIG. 1, the cleaning liquid supply unit 90 is connected to the resupply pipe 35, but may be directly connected to the storage unit 11 of the reaction apparatus 10.

  The cleaning liquid supply unit 90 includes an inert gas supply pipe 91, a dehumidifier 92, a dry inert gas supply pipe 93, a cleaning liquid tank 94, and a cleaning liquid supply pipe 95. The dry inert gas supply pipe 93 forms a flow path connecting the dehumidifier 92 and the cleaning liquid tank 94. The cleaning liquid supply pipe 95 forms a flow path connecting the cleaning liquid tank 94 and the storage unit 11. A valve V <b> 7 is installed in the cleaning liquid supply pipe 95.

  The cleaning liquid tank 94 constitutes a closed space in which the cleaning liquid is stored. Considering the contamination during the nuclide conversion reaction, the washing liquid is optimally heavy water, but other liquids such as light water can also be used.

The nuclide conversion method of this embodiment is demonstrated using FIG.
First, the structure 13 is installed in the reaction apparatus 10, and the storage part 11 and the deuterium low concentration part 12 are airtightly maintained. At this time, no substance that performs nuclide conversion is attached to the structure 13. The electrode 14 is disposed opposite to the structure 13 so as to be separated from the structure 13.

(Electrodeposition liquid supply process)
The heater 56 of the electrodeposition liquid supply unit 50 holds the electrodeposition liquid in the electrodeposition liquid tank 51 at a predetermined temperature (specifically, 25 to 75 ° C.).

  The valve V2 of the discharge part 40 is closed. While the pump 34 of the circulation part 30 operates, the valve V1 installed in the resupply pipe 35 is opened.

  The valve V13 of the inert gas supply pipe 53, the valve V23 of the dry inert gas supply pipe 55, and the valve V3 of the electrodeposition liquid supply pipe 52 are opened. The electrodeposition liquid in the electrodeposition liquid tank 51 is supplied to the storage unit 11 through the electrodeposition liquid supply pipe 52 and the resupply pipe 35.

  When the electrode 14 is immersed in the electrodeposition liquid and a predetermined amount of the electrodeposition liquid is stored in the storage part 11, the valves V1, V3, V13, V23 are closed, and the pump 34 is stopped.

(Electrodeposition layer formation process)
The power supply 15 applies a positive voltage to the electrode 14. The hydrogen storage metal in the electrodeposition liquid is electrodeposited on the surface of the structure 13, and an electrodeposition layer of the hydrogen storage metal is formed. In the electrodeposition layer forming process, a substance that performs nuclide conversion is taken into the electrodeposition layer.

3 to 5 show the result of forming an electrodeposition layer using Cs ( ¹³³ Cs) as the nuclide conversion substance and Pd as the hydrogen storage metal. The experimental conditions are summarized below.
Electrodeposition liquid: Pd electrodeposition liquid (PALLADEX APD-700, manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) added with CsNO ₃ ( ¹³³ Cs) Cs / Pd atomic ratio: 1-1000
Current density: 0.11 to 10 mA / cm ²
Electrode layer thickness: 30 μm
Electrodeposition temperature: 45-55 ° C
Structure: CaO layer (20 nm) / Pd layer (20 nm) alternately stacked on a Pd substrate (0.1 mm), the thickness of the uppermost Pd layer being 10 nm
Area of electrode layer forming region of structure: 6.25 cm ² (2.5 cm × 2.5 cm)

  FIG. 3 is a graph showing the relationship between the Cs / Pd atom number ratio and the Cs adhesion amount. FIG. 4 is a graph showing the relationship between the current density applied to the electrode 14 and the Cs adhesion amount. FIG. 5 is a graph showing the relationship between the film forming speed and the Cs adhesion amount. The amount of deposited Cs was measured by using an inductively coupled plasma mass spectrometer (ICP-MS) obtained by dissolving the electrodeposition layer with an acid.

Under the above conditions, a film forming speed of 0.05 nm / min or more and 100 nm / min or less was obtained.
3 to 5, it can be understood that the higher the Cs / Pd atom number ratio (relatively higher Cs concentration), the more Cs is taken into the electrodeposition layer. There was a tendency that the lower the current density and the slower the film forming speed, the higher the amount of Cs. Although it is generally known that the deposition rate by electrodeposition tends to increase as the current density increases, the results of FIGS. 4 and 5 are contrary to the above tendency. The standard electrode potential of Cs is -2.923 eV, and the standard electrode potential of Pd is 0.915 eV. Under the conditions for electrodeposition of Pd, Cs has a high ionization tendency and is difficult to be electrodeposited. Therefore, it is considered that Cs is hardly taken into the Pd electrodeposition layer. Such a tendency also applies to the case where Sr, Na, Ba, which is a metal having a high ionization tendency (base metal), is a substance subjected to nuclide conversion.

In a conventional method (for example, Patent Document 1) in which a substance subjected to nuclide conversion is added only to the structure surface, a voltage of 1 V and a current density of 0.2 mA / cm ² are obtained in a 0.1 mol / L CsNO ₃ solution. When the electrodeposition is performed for 10 seconds, the Cs adhesion amount is about 0.01 to 0.1 μg / cm ² . Therefore, the adhesion amount of the substance subjected to nuclide conversion can be increased by simultaneous electrodeposition. Adhesion amount when compared to the conventional method, deposition rate, electrodeposition of controllability, and, considering the film efficiency, current density 0.11mA / cm ² or more 10 mA / cm ² or less, more preferably 0. 11mA / cm ² or more 1mA / cm ² or less to be. The film forming speed is 0.05 nm / min to 100 nm / min, more preferably 0.05 nm / min to 1 nm / min.

(Electrodeposition liquid discharge process)
After completion of the electrodeposition layer formation, the valve V2 is opened and the pump 34 is started. The electrodeposition liquid in the storage unit 11 is discharged out of the system through the extraction pipe 31 and the discharge unit 40. The discharged electrodeposition liquid may be collected and returned to the electrodeposition liquid tank 51.

(Washing process)
After the electrodeposition liquid is discharged, a cleaning step may be performed in order to wash away the electrodeposition liquid remaining in the storage unit 11 or the like.

  In the cleaning process, the valve V2 is closed and the valve V1 is opened. Next, the valve V17 of the inert gas supply pipe 91 of the cleaning liquid supply unit 90, the valve V27 of the dry inert gas supply pipe 93, and the valve V7 of the cleaning liquid supply pipe 95 are opened. The cleaning liquid in the cleaning liquid tank 94 is supplied to the storage unit 11 through the cleaning liquid supply pipe 95 and the resupply pipe 35. The cleaning liquid circulates in the storage unit 11 and the circulation unit 30.

  After a predetermined time elapses, the valves V1, V7, V17, V27 are closed and the valve V2 is opened. As a result, the cleaning liquid is discharged out of the system through the discharge unit 40.

(Electrolyte solution supply process)
When the discharge of the electrodeposition liquid or the cleaning liquid (when the cleaning process is performed) is completed, the valve V2 is closed and the valve V1 is opened.

  The valve V14 of the inert gas supply pipe 53, the valve V24 of the dry inert gas supply pipe 55, and the valve V4 of the electrolyte solution supply pipe 62 in the electrolyte solution supply unit 60 are opened. The electrolyte solution in the electrolyte solution tank 61 is supplied to the storage unit 11 through the electrolyte solution supply pipe 62.

  The electrolyte solution in the storage unit 11 is circulated using the circulation unit 30. In this circulation process, the heat exchanger 32 of the circulation unit 30 is heated to a predetermined temperature. In this embodiment, the temperature of the electrolyte solution in the storage unit 11 is maintained at about 20 to 40 ° C.

(Low concentration process)
The concentration reducing means is activated. In the nuclide conversion system 1 of FIG. 1, the vacuum pump 18 of the decompression device 17 is activated, and the deuterium low concentration portion 12 is decompressed. The pressure in the deuterium low concentration part 12 is preferably <0.1 Pa.

When an inert gas supply device is installed as the concentration reducing means, the inert gas is supplied to the deuterium low concentration portion 12 and a predetermined pressure is maintained.
In addition, the deuterium low concentration portion 12 side of the structure 13 is heated to about 70 ° C. by the heater 20.

(Nuclide conversion process)
When the electrode 14 is immersed in the electrolyte solution, the power source applies a voltage to the electrode 14 to generate a voltage difference between the electrode (anode) 14 and the structure (negative electrode) 13. The voltage difference is at least 2V. When the voltage is applied, heavy water is electrolyzed on the surface of the structure 13 on the storage unit 11 side, and deuterium (D ₂ ) is generated. In this embodiment, since the electrolyte solution is used, electrolysis is promoted. When the voltage difference is less than 2 V, the electrolysis reaction does not proceed sufficiently.

When the deuterium concentration is generated on the surface of the storage unit 11 and the deuterium low concentration unit 12 is depressurized (or filled with an inert gas), the surface of the structure 13 on the storage unit 11 side and the deuterium low concentration unit A deuterium concentration gradient is generated between the surface on the 12th side. In addition, when the deuterium low concentration portion 12 side of the structure 13 is heated by the heater 20, a temperature gradient is generated between the surface of the structure 13 on the storage portion 11 side and the surface of the deuterium low concentration portion 12 side. . Due to this concentration gradient and temperature gradient, deuterium flows to the deuterium low concentration portion 12 side and permeates the structure 13. When deuterium permeates, the material subjected to nuclide conversion in the electrodeposition layer is converted into another material. For example, nuclide conversion reactions such as ¹³³ Cs → ¹⁴¹ Pr, ⁸⁸ Sr → ⁹⁶ Mo, ²³ Na → ²⁷ Na → ²⁷ Mg → ²⁷ Al, and ¹³⁸ Ba → ¹⁵⁰ Sm occur. When the material subjected to nuclide conversion is radioactive, it is similarly converted to a stable nuclide. For example, nuclide conversion reactions such as ¹³⁷ Cs → ¹⁵³ Eu and ¹³⁴ Cs → ¹³⁸ La occur. When the electrolyte salt is a salt of the same element as the substance subjected to nuclide conversion, the element derived from the electrolyte salt is also nuclide converted.

FIG. 6 shows the result of carrying out the nuclide conversion reaction using the structure in which the electrodeposition layer in which Pd and Cs are simultaneously electrodeposited is formed. The example of FIG. 6 was produced under the following conditions.
Cs / Pd atomic ratio: 450
Current density during electrodeposition: 0.2 mA / cm ²
Electrode layer thickness: 30 μm
Electrodeposition temperature: 50 ° C
Cs ( ¹³³ Cs) adhesion amount by electrodeposition: 0.5 μg / cm ²
Structure: CaO layer (20 nm) / Pd layer (20 nm) alternately stacked on a Pd substrate (0.1 mm), the thickness of the uppermost Pd layer being 10 nm
Area of deuterium permeable region of structure (reaction area): 2 cm ² (φ16 mm)

The comparative example of FIG. 6 is produced by a conventional method (Patent Document 1) in which a substance that undergoes nuclide conversion is added only to the structure surface. The comparative example of FIG. 6 was produced under the following conditions.
Electrolyte (CsNO ₃ ) solution concentration: 0.1 mol / l
Voltage: 1V
Current density: 0.2 mA / cm ²
Electrodeposition time: 10 seconds Cs ( ¹³³ Cs) adhesion amount: 0.08 μg / cm ²
Area of deuterium permeable region of structure (reaction area): 2 cm ² (φ16 mm)

The nuclide conversion reaction was carried out under the following conditions.
Electrolyte (CsNO ₃ ) solution concentration: 0.1 mol / l
Applied voltage during nuclide conversion reaction: 3.5-30V
Reaction time: 168 hours

In FIG. 6, the result of having implemented the nuclide conversion reaction on the said conditions is shown. In FIG. 6, the vertical axis represents the Pr generation amount. The amount of Pr produced was analyzed using ICP-MS.
The amount of Pr produced was 1.3 × 10 ⁻² μg in the comparative example. On the other hand, in the examples, the amount of Pr produced was 1.2 × 10 ⁻¹ μg. As described above, in the example, the amount of the substance to be subjected to nuclide conversion could be increased, so that the amount of Pr produced could be increased.

  Due to the electrolysis and the nuclide conversion reaction, the amount of heavy water (electrolyte solution) and the electrolyte (when a salt of a substance subjected to nuclide conversion) in the reservoir 11 is decreased, and the electrolyte concentration varies. The electrolyte solution supply unit 60 adjusts the opening degree of the valve V4 and supplies the electrolyte solution from the electrolyte solution tank 61 to the storage unit 11 so as to maintain a predetermined water level at which the electrode 14 can be immersed in the electrolyte solution.

  The heavy water supply unit 65 adjusts the opening degree of the valve V5, and supplies a predetermined amount of heavy water so that the water level in the electrolyte solution tank 61 is maintained. The heater 64 of the electrolyte solution supply unit 60 holds the electrolyte solution at a predetermined temperature (specifically, 20 to 40 ° C.). The electrolyte concentration in the electrolyte solution tank 61 is appropriately adjusted in consideration of the heavy water supply amount from the heavy water supply unit 65, the electrolyte solution temperature, and the amount of the electrolyte solution supplied to the storage unit 11.

  The electrolyte concentration in the reservoir 11 is monitored by known means. When the electrolytic rate is fast and the electrolyte concentration in the storage unit 11 increases, the heavy water replenishment unit 80 is activated and the valve V6 is opened to supply heavy water from the heavy water tank 84 to the storage unit 11. Adjust the electrolyte concentration inside.

When deuterium is generated by the electrolysis of heavy water, oxygen (O ₂ ) is generated. Further, an inert gas (N ₂ or the like) is conveyed to the storage unit 11 along with the electrolyte solution. When the inside of the storage unit 11 becomes 1 atm (1 × 10 ⁵ Pa) or more, the check valve 16 is opened, and the gas is discharged from the storage unit 11.

When the conversion of the material subjected to the nuclide conversion in the electrodeposition layer is completed, the nuclide conversion step is completed. Completion of nuclide conversion is obtained by obtaining in advance the deposition amount and the nuclide conversion rate of the substance subjected to nuclide conversion from the electrodeposition conditions as illustrated in FIGS. Can be calculated and calculated. When the substance subjected to nuclide conversion is a radioactive substance (for example, ¹³⁷ Cs, ¹³⁴ Cs), the radioactivity on the surface of the structure 13 on the storage unit 11 side is measured using a Ge measuring instrument during the nuclide conversion process. It can be determined that the time when the radioactivity amount is below the measurement limit is the end of the nuclide conversion process.

(Electrodeposition layer peeling process)
After completion of the nuclide conversion process, the valves V4, V5, V14, and V24 are closed, and the electrolyte solution supply unit 60 is stopped, so that the supply of the electrolyte solution is stopped. When the heavy water replenishment unit 80 is activated, the valve V6 is closed and the heavy water replenishment unit 80 is stopped.

  The power supply 15 applies a negative voltage opposite to the electrodeposition layer forming step to the electrode 14. The electrodeposition layer elutes from the structure 13 into the electrolyte solution and peels from the structure 13. If the relationship between the current density and the film forming speed (equivalent to the peeling speed) is acquired in advance, the time for only the electrodeposition layer to peel can be obtained. Therefore, the electrodeposition layer peeling step can be time-controlled.

  After a predetermined time has elapsed, the power supply 15 stops applying voltage to the electrodes. The valve V1 is closed and the valve V2 is opened. The electrolyte solution containing the eluted components in the storage unit 11 is discharged out of the nuclide conversion system 1 from the storage unit 11 through the discharge pipe 41 and the discharge unit 40.

  In the nuclide conversion method of this embodiment, without repeating the structure 13, it repeats from an electrodeposition liquid supply process to an electrodeposition layer peeling process. The above-described cleaning step can be performed between the electrodeposition layer peeling step and the electrodeposition liquid supply step.

  In the description of the first embodiment, the cleaning liquid supply unit 90 and the heavy water replenishment unit 80 are used together. However, since the cleaning liquid supply unit 90 and the heavy water replenishment unit 80 have the same configuration, only one of them is used in the present embodiment. May be installed.

Second Embodiment
FIG. 7 is a schematic diagram of a nuclide conversion system according to the second embodiment of the present invention. In FIG. 7, the same components as those in FIG.

  In the nuclide conversion system 101 according to the second embodiment, a plurality of reactors 110-1 to 110-n (n is an integer of 2 or more, n = 3 in the case of FIG. 7) are installed. The reactors 110-1 to 110-n are connected in series in the liquid flow direction. The circulation unit 30 connects the most downstream reactor 110-n and the most upstream reactor 110-1. The structure 13 is connected to the power supply 15.

  The electrolyte solution supply unit 60, the heavy water replenishment unit 80, and the electrodeposition liquid supply unit 50 are connected to the circulation unit 30. In the nuclide conversion system 101 of FIG. 7, the cleaning liquid supply unit is omitted, and the heavy water replenishment unit 80 also serves as the cleaning liquid supply unit. The deuterium low concentration portion 12 of each of the reaction devices 110-1 to 110-n communicates with the decompression device 117. The exhaust pipe 119 connected to each deuterium low concentration portion 12 joins upstream of the vacuum pump 18.

  In the nuclide conversion system 101, as described in the first embodiment, the electrodeposition liquid supply process to the electrodeposition layer peeling process are performed.

  In the configuration of the second embodiment, the electrodeposition layer can be formed on a plurality of structures in one system and the nuclide conversion reaction can be performed, so that the processing efficiency can be increased.

<Third Embodiment>
FIG. 8 is a schematic diagram of a nuclide conversion system according to the third embodiment of the present invention. In FIG. 8, the same components as those in FIG.

  In the nuclide conversion system 201 according to the third embodiment, a plurality of reactors 210-1 to 210-1-n (n is an integer of 2 or more, n = 3 in FIG. 8) are installed. The reactors 210-1 to 210-n are connected in parallel in the liquid flow direction. The resupply pipe 235 and the extraction pipe 231 of the circulation unit 230 are branched and connected to the reactors 210-1 to 210-n, respectively.

  The electrolyte solution supply unit 60, the heavy water replenishment unit 80, and the electrodeposition liquid supply unit 50 are connected to the recirculation pipe 235 of the circulation unit 230. Also in this embodiment, the cleaning liquid supply unit is omitted, and the heavy water replenishment unit 80 also serves as the cleaning liquid supply unit.

  Although omitted in FIG. 8, the deuterium low concentration portion 12 of each of the reaction devices 210-1 to 210-n communicates with the decompression device in the same manner as in the second embodiment. The electrode 14 and the structure 13 are connected to a power source.

  In the nuclide conversion system 201, as described in the first embodiment, the electrodeposition liquid supply step to the electrodeposition layer peeling step are performed.

  In the configuration of the third embodiment, since the electrodeposition layer can be formed on a plurality of structures and the nuclide conversion reaction can be performed in one system, the processing efficiency can be increased. In the nuclide conversion system 201 of the third embodiment, the concentration of the electrolyte solution fed to each of the reactors 210-1 to 210-n can be made substantially uniform as compared with the second embodiment connected in series. Setting of operating conditions is easy.

1,101,201 Nuclide conversion system 10,110,210 Reactor 11 Reservoir 12 Deuterium low concentration part 13 Structure 14 Electrode 15 Power supply 16 Check valve 17, 117 Pressure reducing device 18 Vacuum pump 19, 119 Exhaust piping 20 Heater 21 Substrate 22 First layer 23 Second layer 24 Laminate 30, 230 Circulation unit 31,231 Extraction pipe 32 Heat exchanger 33 Filter 34 Pump 35, 235 Resupply pipe 40 Discharge part 41 Discharge pipe 50 Electrodeposition liquid supply part 51 Electrodeposition liquid tank 52 Electrodeposition liquid supply pipes 53, 66, 72, 81, 91 Inert gas supply pipes 54, 67, 73, 82, 92 Dehumidifiers 55, 68, 74, 83, 93 Drying inert Gas supply pipes 56 and 64 Heater 60 Electrolyte solution supply part 61 Electrolyte solution tank 62 Electrolyte solution supply pipe 63 Electrolyte salt 65 Heavy water supply part 69 84 heavy water tank 70 heavy water supply pipe 71 inert gas supply unit 80 heavy water replenishing unit 85 heavy water replenisher pipe 90 the cleaning liquid supply section 94 Solution tank 95 the cleaning liquid supply pipe

Claims (11)

A structure through which deuterium can permeate, a storage section and a deuterium low-concentration section that form a closed space by the structure, and is stored in the storage section, and is disposed opposite to the surface of the structure on the storage section side. At least one reactor comprising an electrode;
An electrodeposition liquid supply unit that supplies an electrodeposition liquid containing a substance subjected to nuclide conversion and a hydrogen storage metal to the storage unit;
An electrolyte solution supply unit for supplying a heavy aqueous solution containing an electrolyte to the storage unit;
A discharge unit for discharging the aqueous solution containing the electrodeposition liquid and the electrolyte from the storage unit;
A nuclide conversion system comprising: a power source connected to the electrode. The structure includes a substrate made of the hydrogen storage metal or a hydrogen storage alloy, a first layer made of the hydrogen storage metal or the hydrogen storage alloy on the substrate, and the hydrogen storage metal or the hydrogen storage alloy. Second layers made of a material having a relatively low work function are alternately laminated, and the substrate is directed to the deuterium low concentration portion side,
2. The nuclide conversion system according to claim 1, wherein an electrodeposited layer including a substance to be subjected to the nuclide conversion and the hydrogen storage metal or the hydrogen storage alloy is formed on a surface opposite to the substrate.   3. The nuclide conversion system according to claim 1, wherein, when the electrodeposition liquid is stored in the reservoir, the power source applies a current having a predetermined current density to the electrode.   The decompression device for decompressing the inside of the deuterium low concentration portion or the inert gas supply device for supplying an inert gas to the deuterium low concentration portion is connected to the deuterium low concentration portion. The nuclide conversion system according to claim 3.   The nuclide conversion system according to any one of claims 1 to 4, further comprising a cleaning liquid supply unit that supplies a cleaning liquid to the storage unit, wherein the cleaned cleaning liquid is discharged from the discharge unit. A structure through which deuterium can permeate, a storage section and a deuterium low-concentration section that form a closed space by the structure, and is stored in the storage section, and is disposed opposite to the surface of the structure on the storage section side. A nuclide conversion method using a nuclide conversion system having at least one reactor including an electrode,
Supplying an electrodeposition liquid containing a substance subjected to nuclide conversion and a hydrogen storage metal to the reservoir, and immersing the structure in the electrodeposition liquid; and
After the electrodeposition liquid supply step, a voltage of a predetermined value is caused to flow between the electrode and the structure by passing a current of a predetermined value through an electrode disposed opposite to the surface of the structure on the reservoir side, An electrodeposition layer forming step of forming an electrodeposition layer containing the hydrogen storage metal and the substance subjected to the nuclide conversion on the surface of the structure on the storage portion side;
After forming the electrodeposition layer, an electrodeposition liquid discharging step of discharging the electrodeposition liquid from the reservoir,
After the electrodeposition liquid is discharged, a heavy aqueous solution supplying step of supplying a heavy aqueous solution containing an electrolyte to the reservoir and immersing the structure in the heavy aqueous solution containing the electrolyte;
A deconcentration step for maintaining the deuterium concentration in the deuterium low concentration state; and
A predetermined voltage is applied to the electrode to generate the deuterium from the heavy aqueous solution in a space between the electrode and the structure, and the deuterium permeates the structure, thereby A nuclide conversion step in which the material subjected to the nuclide conversion in the layer is nuclide-converted;
After completion of the nuclide conversion step, an electrodeposition layer peeling is performed in which a voltage difference opposite to that in the electrodeposition layer forming step is generated between the electrode and the structure to peel the electrodeposition layer from the structure. A nuclide conversion method. The structure includes a substrate made of the hydrogen storage metal or a hydrogen storage alloy, a first layer made of the hydrogen storage metal or the hydrogen storage alloy on the substrate, and the hydrogen storage metal or the hydrogen storage alloy. The second layer made of a material having a relatively low work function is alternately laminated,
The nuclide conversion method according to claim 6, wherein the electrodeposition layer is formed on a surface opposite to the substrate. Wherein a base metal material to be subjected to nuclide, the hydrogen-absorbing metal is a noble metal, in the electrodeposited layer forming step, so that the 0.11mA / cm ² or more 10 mA / cm ² or less of the current density, The nuclide conversion method according to claim 6 or 7, wherein an electric current is applied to the electrode.   The substance subjected to the nuclide conversion is a base metal, the hydrogen storage metal is a noble metal, and the deposition rate of the electrodeposition layer in the electrodeposition layer formation step is 0.05 nm / min or more and 100 nm / min or less. The nuclide conversion method according to claim 6 or claim 7.   10. The method according to claim 6, wherein the concentration reduction step is a step of depressurizing the deuterium low concentration portion or a step of supplying an inert gas into the deuterium low concentration portion. Nuclide conversion method.   11. The method according to claim 6, further comprising a cleaning step of supplying a cleaning liquid to the storage portion and cleaning the inside of the storage portion between the electrodeposition liquid discharge step and the heavy aqueous solution supply step. The nuclide conversion method described in 1.

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