System and method for production of helium-3 from heavy water reactor moderator heavy water

Abstract

The present application particularly relates to a method for producing helium-3 from heavy water in a heavy water reactor, comprising: step 1, subjecting the heavy water in a moderator system of a heavy water reactor unit to negative pressure rectification to obtain concentrated high-tritium heavy water; step 2, subjecting the concentrated high-tritium heavy water in step 1 to beta decay to produce helium-3 raw gas; and step 3, subjecting the helium-3 raw gas in step 2 to active carbon adsorption, helium-argon separation and hydrogen isotope gas adsorption to obtain helium-3. The method for producing helium-3 from heavy water in a heavy water reactor avoids technical difficulties and high costs of helium-3 / helium-4 isotope separation, and has high technical maturity and good economy.

Description

Technical Field

[0001] This invention relates to the field of nuclear technology application technology, and in particular to a system and method for producing helium-3 from heavy water, a moderator in a heavy water reactor. Background Technology

[0002] Helium-3 has a wide range of applications. For example, it is used as an energy fuel in nuclear fusion reactors to produce highly efficient nuclear power without generating waste, and its radioactivity is negligible, potentially making it a crucial raw material for meeting the long-term energy needs of humanity. Helium-3 is also used to manufacture helium-3 neutron detectors, which have important applications in defense, industry, environmental protection, and cryogenics. Helium-3 is an ideal sample for nuclear magnetic resonance imaging (NMR), offering unparalleled advantages over other isotopes in modern clinical medicine and chemical product structure analysis. Furthermore, helium-3 can be used in isotope mass spectrometry research in archaeology, geology, and hydrology; to search for dark matter in the universe; as a raw material for nuclear weapons; as a working fluid in laser amplifiers; as a surface probe; and to study solar activity. However, as one of the two stable isotopes of hydrogen in nature, helium-3 is extremely rare, with an atomic abundance of only 0.000137% in natural helium gas, far from meeting the needs of current applications and research.

[0003] The Qinshan Phase III heavy water reactor unit is a CANDU-6 type reactor imported from Canada, with a total installed capacity of 2×728 Mwe. Heavy water is used as both a moderator and coolant. During reactor operation, the heavy water is irradiated by neutrons to generate tritium, as shown in the following reaction formula: 2 H + n → 3 H. Compared to light water reactors, heavy water reactors produce more tritium in the form of DTO. The moderator system is the main source of tritium in heavy water reactors, with an assembly capacity of 262 tons per unit. During normal operation, over 90% of the moderator heavy water remains in the reactor core and is irradiated by neutrons, generating tritium. Therefore, tritium generated by the moderator heavy water accounts for 97% of the total tritium production in the entire power plant. The formula for the tritium concentration change in the moderator heavy water is: A T =3.42×10 12 ×〔1-e -1.99×10-9t 〕, where t is the reactor's full-power operating time.

[0004] Heavy water reactor nuclear power plants produce large amounts of tritium annually. Tritium is a low-toxicity nuclide that emits beta particles with a maximum energy of 18 keV, has a half-life of 12.3 years, and its radiation has a short range, posing minimal external radiation hazard to humans. Monomeric tritium molecules include HT, DT, and T. 2Less than one-thousandth of tritium is absorbed by lung tissue, and very little is absorbed through the skin, thus posing minimal harm to the human body. However, tritium oxides, such as HTO, DTO, and T2O, are more harmful than the same amount of monomeric tritium molecules. Almost 100% of tritium-containing water vapor is absorbed by lung tissue and skin, distributing throughout the body and causing internal irradiation. The effective half-life of tritium in the body is 12 days. Tritium emitted from nuclear power plants enters the body through respiration, skin penetration, and consumption of vegetables, meat and animal products, and seafood, causing internal irradiation and a uniform effect throughout the body. Therefore, reducing tritium emissions is extremely important, and the fundamental measure to reduce tritium emissions is to lower the specific activity of tritium in the unit's coolant and moderator. Summary of the Invention

[0005] Therefore, it is necessary to provide a system and method for producing helium-3 from heavy water used as a moderator in heavy water reactors, specifically for high-tritium heavy water in heavy water reactor units.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for producing helium-3 from heavy water, a moderator in a heavy water reactor, includes the following steps:

[0008] Step 1: The moderator heavy water in the moderator system of the heavy water reactor unit is subjected to negative pressure distillation to obtain concentrated high-tritium heavy water;

[0009] Step 2: The concentrated high-tritium heavy water from Step 1 undergoes β decay to produce helium-3 feed gas;

[0010] Step 3: The helium-3 raw material gas from step 2 is subjected to activated carbon adsorption, helium-argon separation, and hydrogen isotope gas adsorption to obtain helium-3.

[0011] Further, in step 1, the moderator heavy water in the moderator system of the heavy water reactor unit includes D2O, DTO, and impurity gases dissolved in D2O and DTO, wherein the impurity gases include at least helium-3 and helium-4; the moderator heavy water in the moderator system of the heavy water reactor unit is subjected to negative pressure distillation, with DTO entering the liquid phase and D2O and impurity gases entering the gas phase, to obtain concentrated high-tritium heavy water.

[0012] Furthermore, in step 2, the helium-3 raw material gas includes D2, O2, N2, D2O, DTO, helium-3, argon-40, DT, and T2.

[0013] Furthermore, in step 3, the hydrogen isotope gas includes DT, T2, and D2.

[0014] In one embodiment, the moderator heavy water in the moderator system of the heavy water reactor unit is distilled at an absolute pressure of 7-10 kPa.

[0015] A system for producing helium-3 from heavy water, a moderator in a heavy water reactor, includes a heavy water distillation system, a gas recovery system, and a gas purification system connected in sequence.

[0016] The heavy water distillation system performs negative pressure distillation on the moderator heavy water in the moderator system of the heavy water reactor unit to obtain concentrated high-tritium heavy water, which is then sent to the gas recovery system.

[0017] The concentrated high-tritium heavy water in the gas recovery system undergoes β decay to produce helium-3 raw material gas, which is then sent to the gas purification system.

[0018] The gas purification system performs activated carbon adsorption, helium-argon separation, and hydrogen isotope gas adsorption on the raw material gas to obtain helium-3.

[0019] Furthermore, the moderator heavy water in the heavy water reactor unit moderator system, which undergoes negative pressure distillation in the heavy water distillation system, includes D2O, DTO, and impurity gases dissolved in D2O and DTO, wherein the impurity gases include at least helium-3 and helium-4; the heavy water distillation system performs negative pressure distillation on the moderator heavy water in the heavy water reactor unit moderator system, with DTO entering the liquid phase and D2O and impurity gases entering the gas phase, to obtain concentrated high-tritium heavy water.

[0020] Furthermore, the heavy water distillation system includes a heavy water detritium removal tower, used to perform negative pressure distillation of the moderator heavy water in the moderator system of the heavy water reactor unit under vacuum equipment assistance. DTO enters the liquid phase, while D2O and impurity gases enter the gas phase, thereby obtaining concentrated low-tritium heavy water and impurity gases at the top of the heavy water detritium removal tower and concentrated high-tritium heavy water at the bottom of the heavy water detritium removal tower.

[0021] Furthermore, the heavy water distillation system also includes a heavy water upgrading tower, with the top product outlet of the heavy water detritium removal tower connected to the feed inlet of the heavy water upgrading tower. The heavy water upgrading tower is used to perform negative pressure distillation of the concentrated low-tritium heavy water and impurity gas at the top of the heavy water detritium removal tower, as well as H2O that leaks into the heavy water distillation system, under the assistance of vacuum equipment. D2O enters the liquid phase, while H2O and impurity gas enter the gas phase, thereby obtaining H2O and impurity gas at the top of the heavy water upgrading tower and concentrated heavy water at the bottom of the heavy water upgrading tower.

[0022] Furthermore, both the heavy water detritium removal tower and the heavy water upgrading tower are composed of one or more cascaded heavy water distillation towers.

[0023] In one embodiment, the heavy water distillation system includes a feed tank, a primary heavy water distillation column, a secondary heavy water distillation column, a tertiary heavy water distillation column, a vacuum pump, a concentrated heavy water storage tank, a reboiler A, a heat exchanger A, a heat exchanger B, a reboiler B, a heat exchanger C, and a reboiler C.

[0024] The feed box is connected to the first feed inlet of the secondary heavy water distillation column, the bottom product outlet of the secondary heavy water distillation column is connected to the first feed inlet of the tertiary heavy water distillation column, the top product outlet of the tertiary heavy water distillation column is connected to the first feed inlet of the secondary heavy water distillation column, the top product outlet of the secondary heavy water distillation column is connected to the feed inlet of the primary heavy water distillation column, the primary heavy water distillation column is connected to a vacuum pump, and the bottom product outlet of the primary heavy water distillation column is connected to a concentrated heavy water storage tank.

[0025] The first-stage heavy water distillation column is equipped with a heat exchanger A at the top and a reboiler A at the bottom. The second-stage heavy water distillation column is equipped with a heat exchanger B at the top and a reboiler B at the bottom. The third-stage heavy water distillation column is equipped with a heat exchanger C at the top and a reboiler C at the bottom.

[0026] Furthermore, the gas recovery system includes a concentrated high-tritium heavy water storage tank, a transfer pump, and a helium-3 feed gas storage tank. The bottom product outlet of the heavy water detritium removal tower is connected in sequence to the transfer pump and the concentrated high-tritium heavy water storage tank. The gas space of the concentrated high-tritium heavy water storage tank is connected to the helium-3 feed gas storage tank.

[0027] Furthermore, the helium-3 feedstock gases used in the gas purification system for activated carbon adsorption, helium-argon separation, and hydrogen isotope gas adsorption include D2, O2, N2, D2O, DTO, helium-3, argon-40, DT, and T2; the hydrogen isotope gases include DT, T2, and D2.

[0028] Furthermore, the gas purification system includes an activated carbon column, a helium-argon separation device, a top circulation device, and a product gas storage tank; the outlet of the helium-3 raw material gas storage tank is connected to the inlet of the activated carbon column, the outlet of the activated carbon column is connected to the inlet of the helium-argon separation device, the outlet of the helium-argon separation device is connected to the inlet of the top circulation device, and the outlet of the top circulation device is connected to the product gas storage tank.

[0029] Furthermore, the activated carbon column includes a shell, a cold trap, an electric furnace, activated carbon, and a filter screen. The shell and the electric furnace are both placed inside the cold trap, and the cold source for the cold trap is nitrogen. Activated carbon is placed inside the shell, and the electric furnace is surrounded by the shell. The shell has an outlet and an inlet, and the outlet is equipped with a filter screen.

[0030] Furthermore, the helium-argon separation device includes a liquefier, a gas-liquid separator, a refrigeration heat exchanger, a cryogenic freezer, and an air-bath vaporizer; the outlet of the activated carbon column is sequentially connected to the liquefier, the gas-liquid separator, the refrigeration heat exchanger, the air-bath vaporizer, and the inlet of the top circulation device, and the refrigeration heat exchanger is connected to the cryogenic freezer.

[0031] Furthermore, the top circulation device includes a target tube.

[0032] Beneficial technical effects of the present invention:

[0033] The system and method for producing helium-3 from heavy water moderator water in the heavy water reactor of the present invention first uses distillation technology to remove helium-4 dissolved in the moderator heavy water to achieve helium-3 production without helium-4. Then, reliable purification technology is used to remove deuterium-tritium gas, deuterium-tritium water vapor, and covering gas argon to directly produce high-purity helium-3 product. Technically, this avoids the technical difficulties and high costs of helium-3 / helium-4 isotope separation, and has high technical maturity and good economic efficiency.

[0034] The two heavy water reactor units at Qinshan are operating safely and stably, laying the foundation for stable helium-3 production. The system and method for producing helium-3 using heavy water as a moderator in the heavy water reactor, as described in this invention, are expected to produce more than 1,000 liters of helium-3 annually from the two units in 5 years and more than 1,500 liters in 10 years, providing a strong guarantee for the country's helium-3 supply. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the system structure for producing helium-3 from heavy water in a heavy water reactor moderator in Example 1.

[0036] Figure 2 This is a schematic diagram of the activated carbon column structure;

[0037] Figure 3 This is a schematic diagram of helium-argon separation;

[0038] Figure 4 The content of helium-4 in the liquid phase inside the heavy water detritium removal tower in Example 2;

[0039] Figure 5 The content of helium-4 in the vapor phase inside the heavy water detritium removal tower in Example 2.

[0040] In the diagram, 1. Feed box; 2. First-stage heavy water distillation column; 3. Second-stage heavy water distillation column; 4. Third-stage heavy water distillation column; 5. Vacuum pump; 6. Concentrated heavy water storage tank; 7. Reboiler A; 8. Heat exchanger A; 9. Heat exchanger B; 10. Reboiler B; 11. Heat exchanger C; 12. Helium-argon separation unit; 13. Activated carbon column; 14. Top circulation device; 15. Helium-3 feed gas storage tank; 16. Product gas storage tank; 17. Concentrated high-tritium heavy water storage tank; 18. Transfer pump; 19. Reboiler C; 20. Liquefaction unit; 21. Gas-liquid separator; 22. Refrigeration heat exchanger; 23. Cryogenic freezer; 24. Air bath vaporizer; 25. Filter screen; 26. Electric furnace; 27. Shell; 28. Cold trap. Detailed Implementation

[0041] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0042] Example 1

[0043] A method for producing helium-3 from heavy water, a moderator in a heavy water reactor, includes the following steps:

[0044] Step 1: The moderator heavy water in the moderator system of the heavy water reactor unit is subjected to negative pressure distillation to obtain concentrated high-tritium heavy water;

[0045] Step 2: Perform β decay on the concentrated high-tritium heavy water from Step 1 to produce helium-3 feed gas;

[0046] Step 3: The helium-3 raw material gas from Step 2 is subjected to activated carbon adsorption, helium-argon separation, and hydrogen isotope gas adsorption to obtain high-purity, high-abundance helium-3.

[0047] In step 1, the moderator heavy water in the moderator system of the heavy water reactor unit includes D2O, DTO, and impurity gases dissolved in D2O and DTO, wherein the impurity gases include at least helium-3 and helium-4; the moderator heavy water in the unit moderator system undergoes negative pressure distillation, with DTO entering the liquid phase and D2O and impurity gases entering the gas phase, to obtain concentrated high-tritium heavy water.

[0048] In step 2, the helium-3 feedstock gases include D2, O2, N2, D2O, DTO, helium-3, argon-40, DT, and T2.

[0049] In step 3, the hydrogen isotope gas includes DT, T2, and D2.

[0050] This embodiment also provides a system for producing helium-3 from heavy water moderator in a heavy water reactor, comprising a heavy water distillation system, a gas recovery system, and a gas purification system connected in sequence.

[0051] The heavy water distillation system performs negative pressure distillation on the moderator heavy water in the moderator system of the heavy water reactor unit to obtain concentrated high-tritium heavy water, which is then sent to the gas recovery system.

[0052] The concentrated high-tritium heavy water in the gas recovery system undergoes β decay to produce helium-3 raw material gas, which is then sent to the gas purification system.

[0053] The gas purification system performs activated carbon adsorption, helium-argon separation, and hydrogen isotope gas adsorption on the helium-3 raw material gas to obtain high-purity and high-abundance helium-3.

[0054] The moderator heavy water in the moderator system of the heavy water reactor unit, which is subjected to negative pressure distillation by the heavy water distillation system, includes D2O, DTO, and impurity gases dissolved in D2O and DTO. The impurity gases include at least helium-3 and helium-4. The heavy water distillation system performs negative pressure distillation on the moderator heavy water in the moderator system of the heavy water reactor unit, with DTO entering the liquid phase and D2O and impurity gases entering the gas phase, to obtain concentrated high-tritium heavy water.

[0055] See Figure 1 The heavy water distillation system includes a feed tank 1, a primary heavy water distillation column 2, a secondary heavy water distillation column 3, a tertiary heavy water distillation column 4, a vacuum pump 5, a concentrated heavy water storage tank 6, a reboiler A 7, a heat exchanger A 8, a heat exchanger B 9, a reboiler B 10, a heat exchanger C 11, and a reboiler C 19.

[0056] The feed box 1 is connected to a feed inlet of the secondary heavy water distillation column 3. The bottom product outlet of the secondary heavy water distillation column 3 is connected to a feed inlet of the tertiary heavy water distillation column 4. The top product outlet of the tertiary heavy water distillation column 4 is connected to a feed inlet of the secondary heavy water distillation column 3. The top product outlet of the secondary heavy water distillation column 3 is connected to a feed inlet of the primary heavy water distillation column 2. The primary heavy water distillation column 2 is connected to a vacuum pump 5. The bottom product outlet of the primary heavy water distillation column 2 is connected to a concentrated heavy water storage tank 6.

[0057] The first-stage heavy water distillation column 2 is equipped with a heat exchanger A8 at the top and a reboiler A7 at the bottom. The second-stage heavy water distillation column 3 is equipped with a heat exchanger B9 at the top and a reboiler B10 at the bottom. The third-stage heavy water distillation column 4 is equipped with a heat exchanger C11 at the top and a reboiler C19 at the bottom.

[0058] Both the secondary heavy water distillation column 3 and the tertiary heavy water distillation column 4 are heavy water detritium removal columns, used to perform negative pressure distillation on the moderator heavy water in the moderator system of the heavy water reactor unit. DTO enters the liquid phase, while D2O and impurity gases enter the gas phase. Thus, concentrated low-tritium heavy water and impurity gases are obtained at the top of the heavy water detritium removal column, and concentrated high-tritium heavy water is obtained at the bottom of the heavy water detritium removal column.

[0059] Working principle of heavy water detritium removal tower: In the heavy water reactor unit's moderator system, the moderator heavy water undergoes gas-liquid mass exchange in the heavy water detritium removal tower. There is a boiling point difference of 0.05℃ between D2O and DTO. The lower boiling point D2O enters the gas phase, while the higher boiling point DTO enters the liquid phase. Thus, concentrated low-tritium heavy water and impurity gases are obtained at the top of the heavy water detritium removal tower, and concentrated high-tritium heavy water is obtained at the bottom of the heavy water detritium removal tower.

[0060] Because the heavy water distillation system operates under vacuum, a small amount of air leaks into the system from the plant. This air contains water vapor, which introduces H2O into the system. Therefore, a primary heavy water distillation column 2 is installed as a heavy water upgrading column. This column performs negative pressure distillation on the concentrated low-tritium heavy water and impurity gases at the top of the detritium removal column, as well as the leaked H2O. D2O enters the liquid phase, while H2O and impurity gases enter the gas phase. This results in H2O and impurity gases at the top of the heavy water upgrading column, and concentrated heavy water at the bottom, preventing the heavy water from being downgraded within the system. The H2O and impurity gases at the top of the heavy water upgrading column are discharged through a vacuum pump 5.

[0061] In the heavy water distillation system, DTO entering the liquid phase is sent from the bottom of the secondary heavy water distillation column 3 to the tertiary heavy water distillation column 4 via a bottom transfer pump. After negative pressure distillation, concentrated high-tritium heavy water is obtained at the bottom of the tertiary heavy water distillation column 4. D2O and impurity gases entering the gas phase are sent from the tertiary heavy water distillation column 4 through the secondary heavy water distillation column 3 via an inter-column gas guide pipe to the primary heavy water distillation column 2. After negative pressure distillation, H2O and impurity gases are obtained at the top of the heavy water upgrading column, and concentrated heavy water is obtained at the bottom of the heavy water upgrading column. The H2O and impurity gases at the top of the heavy water upgrading column are sent to the steam recovery system for treatment via a vacuum pump 5, and the concentrated heavy water at the bottom of the heavy water upgrading column is sent to the concentrated heavy water storage tank 6 via a bottom transfer pump.

[0062] The reboilers at the bottom of the primary heavy water distillation column 2, the secondary heavy water distillation column 3, and the tertiary heavy water distillation column 4 all use 0.45 MPa.A auxiliary steam as a heat source. The tops of the primary heavy water distillation column 2, the secondary heavy water distillation column 3, and the tertiary heavy water distillation column 4 are respectively equipped with a secondary heat exchanger, a tertiary heat exchanger, and a primary heat exchanger. The primary heat exchanger uses circulating cooling water at 34℃~39℃ as a cold source, while the secondary and tertiary heat exchangers both use chilled water at 7℃~12℃ as a cold source.

[0063] The feed rate of the feed box 1 into the secondary heavy water distillation column 3 is 30 kg / h. The bottom discharge rates of the primary heavy water distillation column 2 and the tertiary heavy water distillation column 4 are 28 kg / h and 2 kg / h, respectively. The moderator heavy water in the moderator system of the heavy water reactor unit undergoes gas-liquid mass exchange in the heavy water distillation system. At the bottom discharge port of the tertiary heavy water distillation column 4, concentrated high-tritium heavy water with a concentration greater than or equal to 400 Ci / kg is obtained and sent to the concentrated high-tritium heavy water storage tank 17 for storage. At the bottom discharge port of the primary heavy water distillation column 2, concentrated heavy water with a concentration less than or equal to 13 Ci / kg is obtained.

[0064] The packing materials of the first-stage heavy water distillation column 2, the second-stage heavy water distillation column 3, and the third-stage heavy water distillation column 4 are high-efficiency structured wire mesh packing materials made of phosphor bronze, and the theoretical number of feed plates is designed to be 6; the total theoretical number of plates in the heavy water distillation system is 920.

[0065] The gas recovery system includes a concentrated high-tritium heavy water storage tank 17, a transfer pump 18, and a helium-3 feed gas storage tank 15. The bottom product outlet of the three-stage heavy water distillation column 4 is sequentially connected to the transfer pump 18 and the concentrated high-tritium heavy water storage tank 17. The gas space of the concentrated high-tritium heavy water storage tank 17 is connected to the helium-3 feed gas storage tank 15. The helium-3 gas generated by the decay of the concentrated high-tritium heavy water in the concentrated high-tritium heavy water storage tank 17 is sent to the helium-3 feed gas storage tank 15 via a compressor.

[0066] The concentrated high-tritium heavy water stored in the concentrated high-tritium heavy water storage tank 17 releases energy during tritium decay to produce helium-3, which in turn causes the heavy water to decompose under irradiation, producing deuterium and oxygen. At the same time, inert gas argon is added as a covering gas to prevent DT and T2 explosions. Therefore, the raw material gas produced by the concentrated high-tritium heavy water storage tank 17 is a mixture whose main components are D2, O2, N2, D2O, DTO, helium-3, argon-40, DT and T2.

[0067] The gas purification system uses helium-3 feed gases, including D2, O2, N2, D2O, DTO, helium-3, argon-40, DT, and T2, for activated carbon adsorption, helium-argon separation, and hydrogen isotope gas adsorption; the hydrogen isotope gases include DT, T2, and D2.

[0068] The gas purification system includes an activated carbon column 13, a helium-argon separator 12, a top circulation device 14, and a product gas storage tank 16. The outlet of the helium-3 raw material gas storage tank 15 is connected to the inlet of the activated carbon column 13, the outlet of the activated carbon column 13 is connected to the inlet of the helium-argon separator 12, the outlet of the helium-argon separator 12 is connected to the inlet of the top circulation device 14, and the outlet of the top circulation device 14 is connected to the product gas storage tank 16. After being processed by the gas purification system, the helium-3 raw material gas, with high abundance, is sent to the product gas storage tank 16 for storage.

[0069] See Figure 2 The activated carbon column 13 includes a shell 27, a cold trap 28, an electric furnace 26, activated carbon, and a filter screen 25. The shell 27 and the electric furnace 26 are both placed inside the cold trap 28. The cold source of the cold trap 28 is nitrogen. Activated carbon is placed inside the shell 27. The electric furnace 26 is surrounded by the shell. The shell 27 has an outlet and an inlet. The outlet is equipped with a filter screen 25.

[0070] Working principle of activated carbon column 13: After the cold trap is put into operation, nitrogen gas surrounds the shell, and the temperature of activated carbon column 13 will drop to -196℃. Helium-3 feed gas from helium-3 feed gas storage tank 15 enters activated carbon column 13. Under low temperature conditions, O2, N2, D2O, and DTO are liquefied and adsorbed into the activated carbon. Other gases such as helium-3, argon-40, DT, D2, and T2 enter the next stage helium-argon separation unit for further processing. After the activated carbon is saturated, the cold trap is shut down, and an electric furnace is used to heat and vaporize the impurity gases adsorbed in the activated carbon. The vaporized impurity gases are discharged through the outlet of activated carbon column 13, which has a filter screen to prevent activated carbon from being carried out.

[0071] See Figure 3 The helium-argon separation device includes a liquefier 20, a gas-liquid separator 21, a refrigeration heat exchanger 22, a cryogenic freezer 23, and an air-bath vaporizer 24; the outlet of the activated carbon column 13 is sequentially connected to the liquefier 20, the gas-liquid separator 21, the refrigeration heat exchanger 22, the air-bath vaporizer 24, and the inlet of the top circulation device 14, and the refrigeration heat exchanger 22 is connected to the cryogenic freezer 23.

[0072] Working principle of the helium-argon separation unit: The gas flowing through liquefier 20 mainly consists of helium-3, argon-40, DT, and T2. The argon gas is liquefied after passing through liquefier 20, which uses liquid nitrogen as its cold source. More than 90% of the liquefied argon gas is then sent to a liquid argon storage tank for storage. After passing through gas-liquid separator 21, the liquid argon in the gas is further retained. The remaining gas then enters refrigeration heat exchanger 22, which uses helium as its cold source. After the temperature is controlled at -200℃, the remaining argon gas is further removed. The remaining gas mainly consists of helium-3, DT, and T2. These gases are then further degassed through a top circulation device.

[0073] Working principle of top circulation device 14: After the gas is processed by the helium-argon separation device, the remaining main components are helium-3, DT, and T2. The main material filled in the top circulation device 14 is a target tube. The target tube can adsorb DT, T2, and other gases onto the target tube wall, so the remaining main gas is helium-3.

[0074] All other devices in the system are general-purpose devices.

[0075] The system for producing helium-3 using tritium-containing heavy water from the aforementioned heavy water reactor includes the following steps:

[0076] Step 1: Send the moderator heavy water from the moderator system of the heavy water reactor unit to the heavy water distillation system;

[0077] Step 2: Start the heavy water distillation system and put it into normal operation mode;

[0078] Step 3: Adjust the absolute pressure at the top of the first-stage heavy water distillation column 2 to 7-10 kPa and maintain reduced pressure operation;

[0079] Step 4: Adjust the feed rate of feed box 1 into the secondary heavy water distillation column 3 to 30 kg / h, and adjust the bottom discharge rates of primary heavy water distillation column 2 and tertiary heavy water distillation column 4 to 28 kg / h and 2 kg / h respectively.

[0080] Step 5: The moderator heavy water in the moderator system of the heavy water reactor unit undergoes gas-liquid mass exchange in the heavy water distillation system, and is then concentrated high-tritium heavy water with a concentration of greater than or equal to 400 Ci / kg at the bottom outlet of the three-stage heavy water distillation column 4 and sent to the concentrated high-tritium heavy water storage tank 17 for storage.

[0081] Step 6: The concentrated high-tritium heavy water undergoes β decay in the concentrated high-tritium heavy water storage tank 17, and the generated helium-3 feed gas enters the gas space of the concentrated high-tritium heavy water storage tank 17.

[0082] Step 7: The exhaust gas from the top of the concentrated high-tritium heavy water storage tank 17 is sent to the helium-3 raw material gas storage tank 15 for storage via a compressor;

[0083] Step 8: Monitor the gas flow rate and pressure entering the Helium-3 raw material gas storage tank 15;

[0084] Step 9: Once the pressure in the Helium-3 raw material gas storage tank 15 reaches 10 MPa, start the next operation;

[0085] Step 10: Put the activated carbon column 13 into operation and confirm that the temperature of the activated carbon column 13 drops to -196℃;

[0086] Step 11: Put the helium-argon separation device 12 into operation, and adjust the temperature of the liquefier 20 to -165℃; adjust the temperature of the refrigeration heat exchanger 22 to -200℃;

[0087] Step 12: Confirm that the air-bath vaporizer 24 is in operation;

[0088] Step 13: Put the top circulation device 14 into operation and confirm that its inlet and outlet isolation valves are open;

[0089] Step 14: Start vacuum pump 5 to evacuate helium-3 raw material gas storage tank 15 to an absolute pressure of 10 kPa, then close the isolation valve of helium-3 raw material gas storage tank 15 to the vacuum pump circuit and stop vacuum pump 5.

[0090] Step 15: After the raw material gas in the helium-3 raw material gas storage tank 15 is sent into the activated carbon column 13, it enters the helium-argon separation device 12 and the top circulation device 14 in sequence.

[0091] Step 16: Send the treated gas into the product gas storage tank 16;

[0092] The final product gas storage tank 16 has a helium-3 gas concentration of over 99.99%, which meets the requirements.

[0093] Example 2

[0094] The theoretical calculation of the helium-4 content in the concentrated high-tritium heavy water at the bottom of the heavy water detritium removal tower in Example 1 includes the following steps:

[0095] 1. Calculate the solubility of helium-4 in light water.

[0096] The solubility of helium-4 in light water is calculated using the Henry formula:

[0097]

[0098] In the formula, P is the partial pressure of helium-4 gas in atm; x is the mole fraction of helium-4 in light water; H is the Henry coefficient in atm, which is a function of temperature and varies with temperature as shown in Table 1.

[0099] Table 1. Henry's Law coefficient of Helium-4 in light water

[0100]

[0101] 2. Calculate the helium-4 concentration in the moderator heavy water of the heavy water reactor unit's moderator system.

[0102] In the moderator system of a heavy water reactor unit, helium-4 is used as a protective gas with an absolute pressure of 1 atm and a temperature calculated at 20°C.

[0103] Based on the Henry's coefficient data listed in Table 1, the helium-4 concentration in the moderator heavy water of the heavy water reactor unit's moderator system is calculated as follows:

[0104]

[0105] .

[0106] 3. Calculate the helium-4 content in the concentrated high-tritium heavy water at the bottom of the heavy water detritium removal tower.

[0107] 3.1 Estimate the relative volatility α of helium-4 and heavy water.

[0108] Based on the Henry's law coefficient of helium-4 in light water and the vapor pressure data of heavy water at different temperatures, the relative volatility α of helium-4 and heavy water was calculated as shown in Table 2.

[0109] Table 2. Relative volatility α of Helium-4 and heavy water

[0110]

[0111] 3.2 Calculate the helium-4 content in the concentrated high-tritium heavy water at the bottom of the heavy water detritium removal tower according to the total reflux operation.

[0112] The helium-4 content in the concentrated high-tritium heavy water at the bottom of a heavy water detritium removal column operating under total reflux conditions is calculated using the following formula:

[0113] .

[0114] It can be seen that only a few theoretical equilibrium stages are needed; for example, based on the relative volatility calculation at 30℃, five theoretical equilibrium stages are sufficient to achieve the following effect in removing helium-4 from heavy water tritium deionization towers:

[0115] .

[0116] 3.3 Calculate the helium-4 content in the concentrated high-tritium heavy water at the bottom of the heavy water detritium removal tower according to actual operation.

[0117] In actual operation of the heavy water detritium removal tower, the operating pressure is 7-10 kPa absolute pressure, the reflux ratio is 100, the theoretical equilibrium stage is 920, and the feed flow rate is 30 kg.

[0118] The Aspen_Plus software was used to calculate the helium-4 content in the concentrated high-tritium heavy water at the bottom of the heavy water detritium removal tower based on actual operation, and the collection and distribution curves were obtained as follows. Figure 4-5 The mass fraction w of helium-4 in the concentrated high-tritium heavy water at the bottom of the heavy water detritium decontamination tower is 9.5 × 10⁻⁶. -37 .

[0119] Theoretical calculations show that the helium-4 content in the concentrated high-tritium heavy water at the bottom of the heavy water detritium degassing tower is very low, which can achieve the expected degassing goal.

[0120] Example 3

[0121] Everything else is the same as in Example 2, except that, under the same conditions, the helium-4 concentration in the moderator heavy water of the heavy water reactor unit was calculated using Aspen_Plus thermodynamic equilibrium data as follows:

[0122] .

[0123] It can be seen that the calculations differ slightly depending on the database source, but the results are basically the same.

[0124] Example 4

[0125] A helium-4 removal test was conducted on the heavy water upgrade tower disclosed in Example 1 of patent number CN114180661A. The theoretical plate number was 303, and the helium-4 concentration in the moderator heavy water of the heavy water reactor unit moderator system was measured to be 0.972 ppm.

[0126] The mass fraction of helium-4 in the concentrated high-tritium heavy water at the bottom of the heavy water upgrading tower, w, was less than 0.0048 ppm. 0.0048 ppm is the lower limit of the instrument's measurement, and the actual data is much lower than this number. Using Aspen_Plus software, the mass fraction of helium-4 in the concentrated high-tritium heavy water at the bottom of the heavy water upgrading tower under the same conditions was calculated to be 0.082 ppb.

[0127] The experimental results show that the helium-4 content in the concentrated high-tritium heavy water at the bottom of the heavy water upgrading tower is very low, which can achieve the expected degassing goal.

[0128] In the examples, D and T refer to the hydrogen isotope gases deuterium and tritium, respectively.

[0129] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for producing helium-3 from heavy water, a moderator in a heavy water reactor, characterized in that, Includes the following steps: Step 1: The moderator heavy water in the moderator system of the heavy water reactor unit is subjected to negative pressure distillation to obtain concentrated high-tritium heavy water; inert gas argon is added to the concentrated high-tritium heavy water as a covering gas. Step 2: The concentrated high-tritium heavy water from Step 1 undergoes β decay to produce helium-3 feed gas; the helium-3 feed gas includes D2, O2, N2, D2O, DTO, helium-3, argon-40, DT, and T2; Step 3: The helium-3 raw material gas from step 2 is subjected to activated carbon adsorption, helium-argon separation, and hydrogen isotope gas adsorption to obtain helium-3.

2. The method for producing helium-3 from tritium-containing heavy water in a heavy water reactor according to claim 1, characterized in that, In step 1, the moderator heavy water in the moderator system of the heavy water reactor unit includes D2O, DTO, and impurity gases dissolved in D2O and DTO, wherein the impurity gases include at least helium-3 and helium-4; the moderator heavy water in the moderator system of the heavy water reactor unit is subjected to negative pressure distillation, with DTO entering the liquid phase and D2O and impurity gases entering the gas phase, to obtain concentrated high-tritium heavy water.

3. The method for producing helium-3 from tritium-containing heavy water in a heavy water reactor according to claim 1, characterized in that, In step 3, the hydrogen isotope gas includes DT, T2, and D2.

4. The method for producing helium-3 from tritium-containing heavy water in a heavy water reactor according to any one of claims 1-3, characterized in that, The moderator heavy water in the moderator system of the heavy water reactor unit is distilled at an absolute pressure of 7-10 kPa.

5. A system for producing helium-3 from heavy water as a moderator in a heavy water reactor, characterized in that, It includes a heavy water distillation system, a gas recovery system, and a gas purification system connected in sequence; The heavy water distillation system performs negative pressure distillation on the moderator heavy water in the moderator system of the heavy water reactor unit to obtain concentrated high-tritium heavy water, which is then sent to the gas recovery system. In the gas recovery system, argon gas is added as a covering gas to the concentrated high-tritium heavy water, and β decay occurs to produce helium-3 feed gas, which is then sent to the gas purification system. The helium-3 feed gas includes D2, O2, N2, D2O, DTO, helium-3, argon-40, DT, and T2. The gas purification system performs activated carbon adsorption, helium-argon separation, and hydrogen isotope gas adsorption on the helium-3 feedstock gas to obtain helium-3.

6. The system for producing helium-3 from heavy water moderator in a heavy water reactor according to claim 5, characterized in that, The moderator heavy water in the moderator system of the heavy water reactor unit, which is subjected to negative pressure distillation by the heavy water distillation system, includes D2O, DTO, and impurity gases dissolved in D2O and DTO. The impurity gases include at least helium-3 and helium-4. The heavy water distillation system performs negative pressure distillation on the moderator heavy water in the moderator system of the heavy water reactor unit, with DTO entering the liquid phase and D2O and impurity gases entering the gas phase, to obtain concentrated high-tritium heavy water.

7. The system for producing helium-3 from heavy water in a heavy water reactor moderator according to claim 6, characterized in that, The heavy water distillation system includes a heavy water detritium removal tower, which is used to perform negative pressure distillation of the moderator heavy water in the moderator system of the heavy water reactor unit under vacuum equipment assistance. DTO enters the liquid phase, while D2O and impurity gases enter the gas phase, thereby obtaining concentrated low-tritium heavy water and impurity gases at the top of the heavy water detritium removal tower and concentrated high-tritium heavy water at the bottom of the heavy water detritium removal tower.

8. The system for producing helium-3 from heavy water in a heavy water reactor moderator according to claim 7, characterized in that, The heavy water distillation system also includes a heavy water upgrading tower. The top product outlet of the heavy water detritium removal tower is connected to the feed inlet of the heavy water upgrading tower. The heavy water upgrading tower is used to perform negative pressure distillation of concentrated low-tritium heavy water and impurity gas at the top of the heavy water detritium removal tower, as well as H2O that leaks into the heavy water distillation system, with the assistance of vacuum equipment. D2O enters the liquid phase, and H2O and impurity gas enter the gas phase, thereby obtaining H2O and impurity gas at the top of the heavy water upgrading tower and concentrated heavy water at the bottom of the heavy water upgrading tower.

9. The system for producing helium-3 from heavy water moderator in a heavy water reactor according to claim 8, characterized in that, Both the heavy water detritium removal tower and the heavy water upgrading tower are composed of one or more cascaded heavy water distillation towers.

10. The system for producing helium-3 from heavy water moderator heavy water in a heavy water reactor according to claim 9, characterized in that, The heavy water distillation system includes a feed tank (1), a primary heavy water distillation column (2), a secondary heavy water distillation column (3), a tertiary heavy water distillation column (4), a vacuum pump (5), a concentrated heavy water storage tank (6), a reboiler A (7), a heat exchanger A (8), a heat exchanger B (9), a reboiler B (10), a heat exchanger C (11), and a reboiler C (19). The feed box (1) is connected to a feed inlet of the secondary heavy water distillation column (3), the bottom product outlet of the secondary heavy water distillation column (3) is connected to a feed inlet of the tertiary heavy water distillation column (4), the top product outlet of the tertiary heavy water distillation column (4) is connected to a feed inlet of the secondary heavy water distillation column (3), the top product outlet of the secondary heavy water distillation column (3) is connected to a feed inlet of the primary heavy water distillation column (2), the primary heavy water distillation column (2) is connected to a vacuum pump (5), and the bottom product outlet of the primary heavy water distillation column (2) is connected to a concentrated heavy water storage tank (6). The first-stage heavy water distillation column (2) is equipped with a heat exchanger A (8) at the top and a reboiler A (7) at the bottom. The second-stage heavy water distillation column (3) is equipped with a heat exchanger B (9) at the top and a reboiler B (10) at the bottom. The third-stage heavy water distillation column (4) is equipped with a heat exchanger C (11) at the top and a reboiler C (19) at the bottom.

11. The system for producing helium-3 from heavy water moderator heavy water in a heavy water reactor according to claim 7, 8, 9 or 10, characterized in that, The gas recovery system includes a concentrated high-tritium heavy water storage tank (17), a transfer pump (18), and a helium-3 raw material gas storage tank (15). The bottom product outlet of the heavy water detritium tower is connected in sequence to the transfer pump (18) and the concentrated high-tritium heavy water storage tank (17). The gas space of the concentrated high-tritium heavy water storage tank (17) is connected to the helium-3 raw material gas storage tank (15).

12. The system for producing helium-3 from heavy water in a heavy water reactor moderator according to claim 11, characterized in that, The gas purification system includes an activated carbon column (13), a helium-argon separation device (12), a top circulation device (14), and a product gas storage tank (16); the outlet of the helium-3 raw material gas storage tank (15) is connected to the inlet of the activated carbon column (13), the outlet of the activated carbon column (13) is connected to the inlet of the helium-argon separation device (12), the outlet of the helium-argon separation device (12) is connected to the inlet of the top circulation device (14), and the outlet of the top circulation device (14) is connected to the product gas storage tank (16).

13. The system for producing helium-3 from heavy water moderator heavy water in a heavy water reactor according to claim 12, characterized in that, The activated carbon column (13) includes a shell (27), a cold trap (28), an electric furnace (26), activated carbon, and a filter screen (25). The shell (27) and the electric furnace (26) are both placed inside the cold trap (28). The cold source of the cold trap (28) is nitrogen. Activated carbon is placed inside the shell (27). The electric furnace (26) is surrounded by the shell. The shell (27) has an outlet and an inlet. The outlet is equipped with a filter screen (25).

14. The system for producing helium-3 from heavy water moderator heavy water in a heavy water reactor according to claim 12, characterized in that, The helium-argon separation device includes a liquefier (20), a gas-liquid separator (21), a refrigeration heat exchanger (22), a cryogenic freezer (23), and an air-bath vaporizer (24); the outlet of the activated carbon column (13) is connected in sequence to the inlet of the liquefier (20), the gas-liquid separator (21), the refrigeration heat exchanger (22), the air-bath vaporizer (24), and the top circulation device (14), and the refrigeration heat exchanger (22) is connected to the cryogenic freezer (23).

15. The system for producing helium-3 from heavy water moderator heavy water in a heavy water reactor according to claim 12, characterized in that, The top circulation device (14) includes a target tube.

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