Tritium enrichment method and tritium enrichment device

Abstract

The present invention relates to a tritium enrichment method comprising: a water electrolysis reaction step of converting hard water in a sample, which includes distilled water containing tritium water and hard water (H2O), into hydrogen by a water electrolysis reaction with respect to the sample; and a recirculation step of recirculating oxygen gas, hydrogen gas and residual distilled water released from the water electrolysis reaction, back to the sample, wherein the water electrolysis reaction step comprises cooling the sample through a cooling water flow path provided inside a polymer electrolyte membrane (PEM) water electrolysis stack.

Description

Tritium enrichment method and tritium enrichment device

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2023-0108288, filed August 18, 2023, the entire contents of which are incorporated herein by reference.

[0003]

[0004] Technology field

[0005] The present invention relates to a tritium enrichment method and a tritium enrichment device capable of effectively enriching tritium.

[0006]

[0007] Tritium, a beta nuclide ( 3 H) generally exists in the form of HTO, DTO, T2O, etc. in water samples, and the concentration of tritium in water samples is generally measured by distilling the sample using the distillation method and measuring it using a liquid scintillation counter (LSC). However, when measuring the concentration of tritium in distilled water using the general distillation method, it is measured lower than the detection limit of the liquid scintillation counter. Therefore, in order to measure the concentration of tritium, a sample enriched in tritium must be obtained first.

[0008] Meanwhile, electrolysis is used to concentrate tritium in water samples. When water is electrolyzed, light water (H2O) decomposes into hydrogen, but tritium remains intact. Therefore, electrolysis can be used to concentrate low concentrations of tritium in water samples to levels above the detection limit.

[0009] A representative tritium enrichment technology using electrolysis is alkaline electrolysis. This method involves dissolving an electrolyte in a water sample to create an electrolyte solution, which is then used as a medium to electrolyze the water sample at each electrode.

[0010] However, the alkaline water electrolysis method may have a problem in that the current density may decrease because the hydrogen gas and oxygen gas generated at each electrode cover the electrode surface or the reaction area of ​​the electrode may decrease as the water level decreases during the electrolysis. In addition, since the hydrogen gas and oxygen gas generated in the alkaline water electrolysis method are generated inside the same cell, the stability problem may occur due to the mixing of hydrogen gas and oxygen gas. Furthermore, the water sample enriched in tritium after alkaline water electrolysis still contains the electrolyte. When a sample containing the electrolyte is measured with a liquid scintillation counter, the interference of light due to the electrolyte may occur and the measurement sensitivity may decrease, so there is a problem in that an additional distillation process is required to measure the concentration of tritium.

[0011]

[0012] The present invention is intended to solve the above-described problem, and provides a method and device for concentrating tritium using a water electrolysis method, which improves stability by separating the generated gas while operating at a high current density, and does not require an additional distillation process, and a method and device for concentrating tritium.

[0013]

[0014] According to one embodiment of the present invention, a method for concentrating tritium can be provided, comprising a water electrolysis reaction step of converting light water in a sample containing tritium water and distilled water containing light water (H2O) into hydrogen by a water electrolysis reaction on the sample, and a recirculation step of recycling oxygen gas, hydrogen gas, and residual distilled water discharged from the water electrolysis reaction to the sample side, wherein the water electrolysis reaction step includes cooling the sample through a cooling water channel provided inside a PEM (Polymer Electrolyte Membrane) water electrolysis stack.

[0015] In addition, according to one embodiment of the present invention, a tritium concentration device can be provided, including a water electrolysis treatment unit that transfers a sample including distilled water containing tritium water and light water, and performs an electrolysis reaction to convert light water in the sample into hydrogen, and a sample recirculation unit that recirculates oxygen gas, hydrogen gas, and residual distilled water discharged from the water electrolysis treatment unit to a sample storage unit, wherein the water electrolysis treatment unit includes a PEM (Polymer Electrolyte Membrane) water electrolysis stack having a cooling water path provided therein.

[0016]

[0017] According to the tritium enrichment method and tritium enrichment device of the present invention, the tritium enrichment time can be shortened by operating at a high current density during tritium enrichment, the stability can be improved by separating the hydrogen gas and oxygen gas produced, and the concentration of tritium can be measured immediately without an additional distillation process to remove the electrolyte.

[0018]

[0019] Figure 1 is a schematic diagram showing a tritium enrichment method according to one embodiment of the present invention.

[0020] FIG. 2a is a schematic diagram showing a cooling water passage provided inside an end plate of a PEM electrolysis stack according to one embodiment of the present invention, and FIG. 2b is an actual image of a cooling water passage provided inside an end plate of a PEM electrolysis stack according to one embodiment of the present invention.

[0021] Figure 3 is a schematic diagram showing a tritium enrichment device according to one embodiment of the present invention.

[0022]

[0023] Hereinafter, embodiments of the disclosed invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided to fully convey the spirit of the present invention to those skilled in the art. The disclosed invention is not limited to the embodiments presented herein and may be embodied in other forms. To clarify the disclosed invention, the drawings may omit portions irrelevant to the description, and the sizes of components may be slightly exaggerated to facilitate understanding.

[0024] Throughout the specification, whenever a part is said to "include" a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise stated.

[0025] Singular expressions include plural expressions unless the context clearly indicates otherwise.

[0026] A method for concentrating tritium according to one embodiment of the present invention may include a water electrolysis reaction step of converting light water in a sample containing tritium water and distilled water containing light water (H2O) into hydrogen by a water electrolysis reaction, and a recirculation step of recycling oxygen gas, hydrogen gas, and residual light distilled water discharged from the water electrolysis reaction to the sample side.

[0027] Specifically, in the electrolysis reaction step, a electrolysis reaction may be performed to concentrate tritium. Through the electrolysis reaction, light water in the sample is converted into hydrogen, while tritium water in the sample remains undissociated and can be concentrated. According to an embodiment of the present invention, the tritium concentration in the final sample can be concentrated up to 50 times compared to the initial sample.

[0028] Next, in the recirculation step, the oxygen gas and hydrogen gas generated by the electrolysis reaction and the remaining distilled water that did not participate in the electrolysis reaction can be recycled to the sample side.

[0029] Typically, in the case of PEM water electrolysis for hydrogen production, the sample is discharged without being circulated. However, in the case of PEM water electrolysis for tritium enrichment, the sample is recycled in a closed system to increase the tritium enrichment efficiency. Meanwhile, the oxygen gas and hydrogen gas recycled to the sample side are discharged to the outside through the degassing unit, and the remaining distilled water recycled to the sample side can be converted back into hydrogen through a water electrolysis reaction. Therefore, the tritium enrichment efficiency can be improved through the above-mentioned recycling step.

[0030] The above electrolysis reaction step may include cooling the sample through a cooling water path provided inside a PEM (Polymer Electrolyte Membrane) electrolysis stack.

[0031] Figure 1 is a schematic diagram illustrating a tritium enrichment method according to an embodiment of the present invention. Referring to Figure 1, it can be confirmed that the tritium enrichment method according to an embodiment of the present invention can enrich tritium by utilizing a PEM electrolysis stack, and electrolyzes a sample by utilizing a polymer electrolyte membrane within the PEM stack as an electrolyte.

[0032] Meanwhile, since the oxygen gas and hydrogen gas generated through the electrolysis reaction move through the fluid path inside the PEM electrolysis stack and do not affect the electrode surface, the electrolysis reaction can be performed while maintaining a high current density, thereby shortening the tritium enrichment time. Specifically, in the case of the conventional alkaline electrolysis method, it takes about 30 days from collecting a sample to enriching tritium and measuring it with a liquid scintillation counter, whereas the tritium enrichment method according to an embodiment of the present invention only takes about 10 days from collecting a sample to enriching tritium and measuring it with a liquid scintillation counter by applying the PEM electrolysis method.

[0033] A cooling water passage is provided inside the PEM electrolysis stack to suppress the temperature rise due to internal heat generation from the electrolytic reaction. In general, in the case of the PEM electrolysis method for hydrogen production, separate cooling is not provided to reduce the internal resistance of the PEM stack to enable stable operation. However, in the PEM electrolysis method for tritium enrichment, separate cooling is required because when the temperature of the sample rises, some of the tritium water and light water contained in the sample may vaporize together, lowering the tritium enrichment level. Therefore, in the tritium enrichment method according to the present invention, a cooling water passage is provided inside the PEM electrolysis stack to prevent a decrease in the tritium enrichment level due to vaporization of the sample.

[0034] The above cooling water path can be provided inside the end plate of the PEM electrolysis stack.

[0035] FIG. 2a is a schematic diagram showing a cooling water passage provided inside an end plate of a PEM electrolysis stack according to one embodiment of the present invention, and FIG. 2b is an actual image of a cooling water passage provided inside an end plate of a PEM electrolysis stack according to one embodiment of the present invention.

[0036] Referring to FIGS. 2A and 2B, it can be seen that the cooling water passage is arranged in a grid shape parallel to the end plate within the end plate of the PEM electrolysis stack. Accordingly, the cooling water passage can be arranged so as not to obstruct the path of the fluid passage through which oxygen gas, hydrogen gas, and residual distilled water discharged from the electrolysis reaction move.

[0037] The above recycling step may include removing catalyst ions in the residual distilled water through an ion exchange resin.

[0038] The above PEM electrolysis stack utilizes a precious metal catalyst doped into the MEA (Membrane Electrode Assembly). During electrolysis in the PEM electrolysis stack, some of the precious metal catalyst may fall off, which may increase the concentration of catalyst ions in the remaining distilled water. If the concentration of catalyst ions in the remaining distilled water increases in this way, the resistance in the PEM electrolysis stack may increase, making stable operation difficult. Therefore, the tritium enrichment method according to one embodiment of the present invention aims to remove catalyst ions in the remaining distilled water and maintain an ultrapure state by arranging an ion exchange resin in the recirculation stage so as to stably enrich tritium.

[0039] The above ion exchange resin can be an ion exchange resin capable of removing ions desorbed from the noble metal catalyst. More specifically, an ultrapure water composite ion exchange resin in which a cation exchange resin and an anion exchange resin are mixed can be used. Specifically, a cation exchange resin in which sulfonic acid, carboxylic acid, etc. are bound as functional groups, and an anion exchange resin in which trimethylammonium, dimethylethanolammonium, etc. are bound as functional groups can be used.

[0040] The sample introduced into the above electrolysis reaction step can be cooled by a cooling unit.

[0041] As described above, the PEM electrolysis method for tritium enrichment requires separate cooling to prevent the sample from vaporizing and lowering the tritium enrichment level. Therefore, the tritium enrichment method according to one embodiment of the present invention can suppress the reduction in tritium enrichment level by cooling the sample introduced into the electrolysis reaction step using a cooling unit. The cooling unit can utilize, for example, a chiller.

[0042] The above tritium number may include at least one selected from the group consisting of HTO, DTO, and T2O.

[0043] Next, a tritium enrichment device according to another embodiment of the present invention will be described in detail.

[0044] A tritium enrichment device according to one embodiment of the present invention may include a water electrolysis treatment unit that transfers a sample containing distilled water containing tritium water and light water and performs a water electrolysis reaction to convert light water in the sample into hydrogen, and a sample recirculation unit that recirculates oxygen gas, hydrogen gas, and residual distilled water discharged from the water electrolysis treatment unit to a sample storage unit.

[0045] Specifically, in the electrolysis treatment unit, a electrolysis reaction can be performed to concentrate tritium. Through the electrolysis reaction, light water in the sample is converted into hydrogen, while tritium water in the sample remains undissolved and can be concentrated.

[0046] Next, the sample recirculation unit can recirculate the oxygen gas and hydrogen gas generated by the electrolysis reaction and the remaining distilled water that did not participate in the electrolysis reaction to the sample storage unit. Specifically, the oxygen gas and hydrogen gas recycled to the sample storage unit are discharged to the outside through the degassing unit, and the remaining distilled water recycled to the sample storage unit can convert light water into hydrogen again through the electrolysis reaction, thereby improving the concentration efficiency of tritium. The degassing unit can utilize, for example, a bubbler.

[0047] The above electrolysis treatment unit may include a PEM (Polymer Electrolyte Membrane) electrolysis stack having a cooling water path provided therein.

[0048] A tritium concentration device according to one embodiment of the present invention can concentrate tritium by utilizing a PEM electrolysis stack, and can electrolyze a sample by utilizing a polymer electrolyte membrane inside the PEM stack as an electrolyte.

[0049] Meanwhile, since the oxygen gas and hydrogen gas generated through the electrolysis reaction move through the fluid path inside the PEM electrolysis stack and do not affect the electrode surface, the electrolysis reaction can be performed while maintaining a high current density, thereby shortening the tritium enrichment time. Specifically, in the case of the conventional alkaline electrolysis method, it takes about 30 days from collecting a sample to enriching tritium and measuring it with a liquid scintillation counter, whereas the tritium enrichment device according to an embodiment of the present invention only takes about 10 days from collecting a sample to enriching tritium and measuring it with a liquid scintillation counter by applying the PEM electrolysis method.

[0050] The above PEM electrolysis stack may include an end plate, an insulator, a bipolar plate, a gasket, a gas diffusion layer, and an MEA (Membrane Electrode Assembly). The end plate may maintain the sealing of the stack and prevent leakage of each cell, the insulator may prevent electrical collision through insulation, and the bipolar plate may promote an electrical reaction and dissipate heat while assisting fluid circulation between cells. In addition, the gasket may prevent leakage between cells and perform an electrical insulation function, the gas diffusion layer may assist diffusion of oxygen and hydrogen gases delivered to the MEA, and the MEA may be composed of an electrolyte membrane, an anode, and a cathode and may perform a water electrolysis reaction.

[0051] A cooling water path is provided within the PEM electrolysis stack to suppress temperature increases due to internal heat generation resulting from electrolytic reactions. Accordingly, the tritium enrichment device according to the present invention can prevent a decrease in tritium enrichment due to sample vaporization by providing a cooling water path within the PEM electrolysis stack.

[0052] The above cooling water path can be provided inside the end plate of the PEM electrolysis stack.

[0053] The above cooling water path can be arranged in a grid shape parallel to the end plate inside the end plate of the PEM electrolysis stack so as not to obstruct the path of the fluid path through which oxygen gas, hydrogen gas, and residual distilled water discharged from the electrolysis reaction move.

[0054] The sample recirculation unit may further include an ion exchange resin for removing catalyst ions in the residual distilled water.

[0055] During electrolysis in the PEM electrolysis stack, some of the precious metal catalyst doped in the MEA (Membrane Electrode Assembly) of the PEM electrolysis stack may fall off, thereby increasing the concentration of catalyst ions in the remaining distilled water. If the concentration of catalyst ions in the remaining distilled water increases in this way, the resistance in the PEM electrolysis stack may increase, making stable operation difficult. Therefore, the tritium concentration device according to one embodiment of the present invention seeks to remove catalyst ions in the remaining distilled water and maintain an ultrapure state by arranging an ion exchange resin in the sample recirculation section so as to stably concentrate tritium.

[0056] The above sample storage unit may include a cooling unit for cooling the sample.

[0057] As described above, the PEM electrolysis method for tritium enrichment requires separate cooling to prevent the sample from vaporizing and lowering the tritium enrichment level. Therefore, the tritium enrichment method according to one embodiment of the present invention can suppress the reduction in tritium enrichment level by cooling the sample introduced into the electrolysis reaction step using a cooling unit. The cooling unit can utilize, for example, a chiller.

[0058] The sample storage unit may further include a degassing unit for discharging oxygen gas and hydrogen gas discharged from the electrolysis treatment unit. The degassing unit may utilize, for example, a bubbler.

[0059] A tritium enrichment device according to one embodiment of the present invention may further include a timer for stopping the device when the sample is exhausted and for measuring the time required for reaching enrichment. In addition, the sample recirculation unit may further include a peristaltic pump linked to the timer and an infrared sensor for transporting the sample to the electrolysis unit.

[0060] The above PEM electrolysis stack comprises a precious metal catalyst, and the precious metal catalyst may comprise at least one selected from the group consisting of iridium, ruthenium, platinum, nickel, and palladium, preferably iridium and / or ruthenium, and more preferably iridium and ruthenium.

[0061] The above-mentioned precious metal catalyst can be doped into the MEA (Membrane Electrode Assembly) of the PEM electrolysis stack to improve the electrolysis reaction rate and play a role in efficiently concentrating tritium.

[0062] The above PEM may include at least one selected from the group consisting of Nafion, PEEK (Polyetheretherketone), and SPEK (Sulfonated Polyetherketone).

[0063] The fluid path provided in the sample recirculation section may be formed of a tube containing at least one selected from the group consisting of Teflon, PVDF (Polyvinylidene Fluoride), and PI (Polyimide).

[0064] Figure 3 is a schematic diagram showing a tritium enrichment device according to one embodiment of the present invention.

[0065] Referring to FIG. 3, it can be confirmed that a tritium enrichment device according to one embodiment of the present invention includes a water electrolysis treatment unit that converts light water in a sample into hydrogen to enrich tritium, and a sample recirculation unit that recirculates oxygen gas, hydrogen gas, and residual distilled water discharged from the water electrolysis treatment unit to a sample storage unit.

[0066] Hereinafter, the present invention will be described in more detail through examples. However, these examples are provided solely to aid understanding of the present invention and are not intended to limit the scope of the present invention in any way.

[0067]

[0068] {Example}

[0069] <Example 1>

[0070] A distilled water sample was electrolyzed through a PEM electrolysis stack, and then the oxygen gas, hydrogen gas, and residual distilled water discharged from the electrolysis reaction were recycled to the sample side to concentrate tritium. At this time, the PEM polymer electrolyte membrane utilized Nafion 115, a PEM 3-cell stack was used, the precious metal catalyst used Ir, and the fluid path used a Teflon tube. In addition, the sample was cooled to 18℃ by setting the cooling water path provided inside the PEM electrolysis stack and the chiller in the sample storage section to 5℃, and the oxygen and hydrogen gases were discharged to the outside through a bubbler. Meanwhile, tritium concentration was performed by applying a current of 15A from the initial sample amount of 800g until the final sample amount became 30g.

[0071]

[0072] <Example 2>

[0073] Tritium was concentrated in the same manner as in Example 1, except that Ir and Ru were used as precious metal catalysts.

[0074]

[0075] <Comparative Example 1>

[0076] Tritium was concentrated in the same manner as in Example 1, except that the sample was not cooled through the cooling water path provided inside the PEM electrolysis stack and the chiller in the sample storage compartment.

[0077]

[0078] <Example 3>

[0079] Tritium was concentrated in the same manner as in Example 1, except that an ion exchange resin was applied to the sample recirculation section. The ion exchange resin used was MR-450 UPW from DuPont, filled at 1 mL (BV).

[0080]

[0081] <Example 4>

[0082] Tritium was concentrated in the same manner as in Example 3, except that Ir and Ru were used as precious metal catalysts.

[0083]

[0084] <Evaluation 1> Measurement of tritium enrichment time

[0085] As a result of concentrating tritium according to Example 1, the time required for the final sample amount to become 30 g from the initial sample amount of 800 g was 50 hours. Compared to the approximately 500 hours required for tritium concentration using a typical alkaline water electrolysis method, it can be seen that the tritium concentration time in Example 1 was greatly shortened. Therefore, it was confirmed that the tritium concentration method and tritium concentration device according to one embodiment of the present invention significantly shorten the tritium concentration time by maintaining a high current density by applying the PEM water electrolysis method.

[0086]

[0087] <Evaluation 2> Tritium enrichment evaluation

[0088] Tritium concentration was measured using a liquid scintillation counter on the final sample enriched through a tritium enrichment device. The tritium enrichment was assessed by the number of times the tritium concentration in the final sample increased compared to the initial sample, and the results are presented in Table 1 below.

[0089] Tritium concentration (times) Example 112.8 Example 214.3 Example 313.1 Example 415.1 Comparative example 19.9

[0090] Referring to Table 1, Examples 1 to 4 exhibited high tritium enrichment, but Comparative Example 1 exhibited relatively low tritium enrichment. Therefore, it was confirmed that the tritium enrichment method and tritium enrichment device according to one embodiment of the present invention can improve the tritium enrichment by applying a cooling water path provided inside the PEM water electrolysis stack. Meanwhile, it was also confirmed that the tritium enrichment degree was further improved when both Ir and Ru were utilized as a noble metal catalyst in the tritium enrichment device than when Ir was utilized alone.

[0091] Furthermore, in the case of Examples 3 and 4 using ion exchange resin, it was determined that stable tritium enrichment was possible by removing the catalyst ions in the residual hard water.

Claims

1. A water electrolysis reaction step for converting light water in a sample into hydrogen by an electrolysis reaction of a sample containing distilled water containing tritium water and light water (H2O); and A recirculation step for recirculating oxygen gas, hydrogen gas and residual distilled water discharged from the above electrolysis reaction to the sample side; A tritium enrichment method, wherein the above electrolysis reaction step includes cooling the sample through a cooling water channel provided inside a PEM (Polymer Electrolyte Membrane) electrolysis stack.

2. In claim 1, The above electrolysis reaction step is, A method for enriching tritium, comprising cooling the sample through a cooling water channel provided inside the end plate of the PEM electrolysis stack.

3. In claim 2, A tritium enrichment method, wherein the above cooling water path is provided in a grid shape parallel to the end plate.

4. In claim 1, The above recycling step is, A method for concentrating tritium, comprising removing catalyst ions in the residual distilled water through an ion exchange resin.

5. In claim 1, A tritium enrichment method, wherein the sample introduced into the above electrolysis reaction step is cooled by a cooling unit.

6. In claim 1, A method for enriching tritium, wherein the tritium water comprises at least one selected from the group consisting of HTO, DTO and T2O.

7. A water electrolysis treatment unit that transfers a sample containing distilled water containing tritium water and light water and performs an electrolysis reaction to convert light water in the sample into hydrogen; and It includes a sample recirculation unit that recirculates oxygen gas, hydrogen gas, and residual distilled water discharged from the above electrolysis treatment unit to the sample storage unit; The above electrolysis treatment unit is a tritium enrichment device including a PEM (Polymer Electrolyte Membrane) electrolysis stack having a cooling water path provided therein.

8. In claim 7, A tritium enrichment device in which the above cooling water path is provided inside the end plate of the above PEM electrolysis stack.

9. In claim 8, A tritium enrichment device, wherein the above cooling water passage is arranged in a grid shape parallel to the above end plate.

10. In claim 7, A tritium concentration device, wherein the sample recirculation unit further includes an ion exchange resin for removing catalyst ions in the residual distilled water.

11. In claim 7, A tritium enrichment device, wherein the sample storage unit includes a cooling unit for cooling the sample.

12. In claim 7, A tritium enrichment device, wherein the tritium water comprises at least one selected from the group consisting of HTO, DTO and T2O.

13. In claim 7, A tritium enrichment device, wherein the sample storage unit further includes a degassing unit for discharging oxygen gas and hydrogen gas discharged from the electrolysis treatment unit.

14. In claim 7, The above PEM electrolysis stack comprises a precious metal catalyst, A tritium enrichment device, wherein the above precious metal catalyst comprises at least one selected from the group consisting of iridium, ruthenium, platinum, nickel, and palladium.

15. In claim 7, The above PEM is a tritium enrichment device comprising at least one selected from the group consisting of Nafion, PEEK (Polyetheretherketone), and SPEK (Sulfonated Polyetherketone).

16. In claim 7, A tritium enrichment device, wherein the flow path provided in the sample recirculation section is formed of a tube containing at least one selected from the group consisting of Teflon, PVDF (Polyvinylidene Fluoride), and PI (Polyimide).

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