A heavy water reactor unit heavy water recovery and purification system

Abstract

This invention specifically relates to a heavy water recovery and purification system for heavy water reactor units, comprising an ultraviolet (UV) oxidation subsystem, an adsorption-exchange subsystem, a circulating pump, a filtration and oil removal subsystem connected to the UV oxidation and adsorption-exchange subsystems respectively, a negative pressure exhaust filtration subsystem connected to the UV oxidation subsystem, a monitoring subsystem for monitoring heavy water leakage during heavy water reactor unit recovery, and a control subsystem for controlling the start-up and shutdown of the circulating pump, the UV oxidation subsystem, and the negative pressure exhaust filtration subsystem. The inlet of the circulating pump is connected to the filtration and oil removal subsystem and the UV oxidation subsystem respectively, and the outlet of the circulating pump is connected to the UV oxidation subsystem and the adsorption-exchange subsystem respectively. This heavy water recovery and purification system for heavy water reactor units effectively removes ionic impurities, organic matter, and solid particulate matter while preventing the spread of radioactive materials and avoiding the additional generation of radioactive waste.

Description

Technical Field

[0001] This invention relates to the field of heavy water recovery and treatment technology for heavy water reactor units, and in particular to a heavy water recovery and purification system for heavy water reactor units. Background Technology

[0002] Heavy water reactors use heavy water as a moderator and coolant. Heavy water is an important nuclear material, present in only 0.015% of natural water, making its preparation and purification extremely expensive. During operation, some deuterium in the heavy water absorbs neutrons and transforms into tritium. With continuous operation, the tritium concentration in the moderator and coolant accumulates and increases. Tritium is radioactive and undergoes beta decay; ingestion can lead to long-term internal radiation exposure. Therefore, it is essential to recover as much heavy water as possible from the reactor environment in both gaseous and liquid forms to save on costs and limit tritium diffusion. The recovered heavy water typically contains various contaminants such as ionic impurities, organic matter, and particulate matter, requiring purification treatment to meet specific standards before reuse.

[0003] Currently, heavy water reactor units mostly use ion exchange resins and activated carbon to purify and recover heavy water. While ion exchange resins can remove ionic impurities, they are almost ineffective at treating organic matter. Activated carbon has a weak adsorption capacity for organic matter in recovered heavy water, and recalcitrant organic matter in heavy water cannot be removed. Traditional water treatment processes for treating organic matter lack designs for containing and controlling radioactive waste, and therefore cannot be directly applied to the purification of recovered heavy water in heavy water reactor units. For example, reverse osmosis technology produces a certain proportion of wastewater discharge; ultraviolet-assisted oxidation technology lacks closed-loop radioactive containment measures; and chemical oxidation methods increase the amount of resin and activated carbon used, generating more radioactive waste.

[0004] Therefore, a heavy water recovery and purification system and process for heavy water reactor units is needed, which can effectively remove ionic impurities, organic matter and solid particulate matter from tritium-containing heavy water while preventing the spread of radioactivity and avoiding the increase of additional radioactive waste, so that the purified recovered heavy water can meet the heavy water needs of the heavy water reactor. Summary of the Invention

[0005] The purpose of this invention is to provide a heavy water recovery and purification system for heavy water reactor units, which effectively removes ionic impurities, organic matter, and solid particulate matter from the recovered heavy water of heavy water reactor units while preventing the spread of radioactive waste and avoiding the addition of additional radioactive waste, so that the purified recovered heavy water can meet the heavy water needs of heavy water reactor units.

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

[0007] A heavy water recovery and purification system for a heavy water reactor unit includes an ultraviolet oxidation subsystem, a pressure-sealed filtration and oil removal subsystem, an adsorption exchange subsystem, and a negative pressure exhaust filtration subsystem, a monitoring subsystem, a circulating pump, and a control subsystem. The filtration and oil removal subsystem is connected to the pipelines of the ultraviolet oxidation subsystem and the adsorption exchange subsystem. The inlet of the circulating pump is connected to the pipelines of both the filtration and oil removal subsystem and the ultraviolet oxidation subsystem. The outlet of the circulating pump is connected to the pipelines of both the ultraviolet oxidation subsystem and the adsorption exchange subsystem. The negative pressure exhaust filtration subsystem is connected to the pipeline of the ultraviolet oxidation subsystem. The monitoring subsystem monitors gas and liquid leaks in the heavy water recovery and purification system of the heavy water reactor unit. The control subsystem controls the start and stop of the circulating pump, the ultraviolet oxidation subsystem, and the negative pressure exhaust filtration subsystem.

[0008] Furthermore, the filtration and oil removal subsystem includes a filter, an inlet pipe, and an outlet pipe; the filter includes a pressure-bearing sealed housing and a filter element that is detachably fixed inside the pressure-bearing sealed housing; the pressure-bearing sealed housing is provided with an inlet and an outlet, the inlet is connected to the inlet pipe, the outlet is connected to the outlet pipe, and both the inlet and outlet pipes are provided with valves.

[0009] Furthermore, the filter element consists of a stainless steel frame, multiple layers of oil filter paper, and a stainless steel filter screen that are wrapped from the inside out. The filter element is detachably fixed inside the pressure-bearing sealed housing by fixing screws that pass through the stainless steel frame and are threaded to the bottom of the housing.

[0010] Furthermore, the stainless steel filter screen is a 150μm stainless steel filter screen; the multi-layer oil filter paper is a corrugated multi-layer oil filter paper.

[0011] Furthermore, the ultraviolet oxidation subsystem includes an ultraviolet oxidation water tank, an ultraviolet lamp tube, a quartz protective sleeve, a dosing funnel, and a maintenance manhole flange cover; the top of the ultraviolet oxidation water tank is threadedly sealed to the maintenance manhole flange cover; the maintenance manhole flange cover has evenly distributed holes for placing the quartz protective sleeve, and the ultraviolet lamp tube is placed inside the quartz protective sleeve; the opening of the quartz protective sleeve is sealed and fixed by a silicone sealing ring; the cable of the ultraviolet lamp tube passes through the silicone sealing ring and is connected to an external power supply circuit; the quartz protective sleeve and the holes on the maintenance manhole flange cover are connected by... A silicone sealing gasket is used for sealing and fixing; the dosing funnel is connected to the ultraviolet oxidation water tank pipeline for adding hydrogen peroxide into the ultraviolet oxidation water tank; a valve is provided on the pipeline connecting the dosing funnel and the ultraviolet oxidation water tank; the inlet of the circulating pump is connected to the outlet of the ultraviolet oxidation water tank and the outlet pipeline respectively; the outlet of the circulating pump is connected to the inlet pipeline of the ultraviolet oxidation water tank; a valve is provided on the pipeline connecting the inlet of the circulating pump and the outlet of the ultraviolet oxidation water tank; a liquid sampler and a valve are provided on the pipeline connecting the outlet of the circulating pump and the inlet of the ultraviolet oxidation water tank.

[0012] Furthermore, the adsorption exchange subsystem includes an ion exchange resin bed and an activated carbon bed; the outlet of the circulating pump is also connected to the inlet pipe of the activated carbon bed, the outlet of the activated carbon bed is connected to the inlet pipe of the ion exchange resin bed, the outlet of the ion exchange resin bed is connected to the inlet pipe of the ultraviolet oxidation water tank, and the liquid sampler is connected to the pipes connecting the outlet of the ion exchange resin bed to the inlet of the ultraviolet oxidation water tank and the outlet of the circulating pump to the inlet of the ultraviolet oxidation water tank, respectively. A three-way valve is provided on the pipes connecting the outlet of the circulating pump to the inlet of the ultraviolet oxidation water tank and the inlet of the activated carbon bed.

[0013] Furthermore, the circulating pump is a sealed magnetic pump.

[0014] Furthermore, the ion exchange resin bed is filled with nuclear-grade uniform-particle gel-type mixed resin, which is composed of nuclear-grade uniform-particle gel-type H-type strong acid cation resin and OH-type strong base anion resin in a 1:1 stoichiometric ratio.

[0015] Furthermore, the negative pressure exhaust filtration subsystem includes an exhaust fan and a molecular sieve adsorption bed; the gas space of the ultraviolet oxidation water tank is sequentially connected to the inlet pipes of the molecular sieve adsorption bed and the exhaust fan, the outlet of the exhaust fan is connected to the gas space pipe of the ultraviolet oxidation water tank, and a reflux valve is provided on the pipe connecting the outlet of the exhaust fan to the gas space of the ultraviolet oxidation water tank.

[0016] Furthermore, the monitoring subsystem includes a liquid leak detector, a radioactivity monitor, and a micro-pressure gauge; a stainless steel water receiving tray is installed at the bottom of the heavy water reactor unit's heavy water recovery and purification system, and the liquid leak detector is mounted on the lowest point of the stainless steel water receiving tray via a base; the liquid leak detector includes a probe, and the base and probe are a pair of electrodes, with a gap between the probe and the base; when there is leaking water at the lowest point of the stainless steel water receiving tray and the water level rises to the probe position, the two electrodes conduct and generate an alarm;

[0017] The exhaust fan outlet is equipped with a radioactivity monitoring instrument; the radioactivity monitoring instrument monitors the tritium activity of the gas at the exhaust fan outlet; when the tritium activity of the gas at the exhaust fan outlet exceeds the warning value, the radioactivity monitoring instrument issues an alarm.

[0018] The monitoring subsystem also includes a micro-pressure gauge installed on the top of the ultraviolet oxidation water tank, used to monitor the air space pressure of the ultraviolet oxidation water tank.

[0019] Furthermore, the control subsystem controls the start and stop of the circulating pump, ultraviolet lamp tube, and exhaust fan.

[0020] This invention also provides a process for recovering and purifying heavy water in a heavy water reactor unit, comprising the following steps:

[0021] 1. Start the exhaust fan of the negative pressure exhaust filtration subsystem to establish a micro negative pressure of -20Pa to -30Pa in the air space of the ultraviolet oxidation water tank;

[0022] 2. Start the circulation pump to draw the heavy water recovered from the heavy water reactor unit into the heavy water recovery purification system through the inlet quick connector;

[0023] 3. The heavy water recovered by the heavy water reactor unit flows through a filter to remove most of the solid particles and grease;

[0024] 4. The heavy water reactor unit recovers heavy water and puts it into the ultraviolet oxidation water tank. After stopping the circulation pump and controlling the liquid level in the ultraviolet oxidation water tank to not exceed the opening of the dosing funnel, the water supply to the ultraviolet oxidation water tank is stopped.

[0025] 5. The heavy water recovered from the heavy water reactor unit in the ultraviolet oxidation water tank is circulated. Samples are taken using a liquid sampler to determine the initial TOC concentration of the heavy water recovered from the heavy water reactor unit.

[0026] 6. Based on the initial TOC concentration of the heavy water recovered by the heavy water reactor unit, determine the amount of hydrogen peroxide to be added, which should be 6 times the initial TOC concentration of the heavy water recovered by the heavy water reactor unit.

[0027] 7. Turn on the ultraviolet lamp, add sufficient hydrogen peroxide through the dosing funnel, and maintain the self-circulation of the ultraviolet oxidation water tank;

[0028] 8. Periodically take samples using a liquid sampler to analyze the hydrogen peroxide concentration in the heavy water recovered from the heavy water reactor unit in the ultraviolet oxidation water tank until the hydrogen peroxide concentration is less than 2 mg / kg;

[0029] 9. The heavy water recovered from the heavy water reactor unit in the ultraviolet oxidation water tank is fed into the adsorption exchange subsystem, and then returns to the ultraviolet oxidation water tank after passing through the activated carbon bed and the ion exchange resin bed in sequence.

[0030] 10. Take samples using a liquid sampler and measure various purification indicators of the heavy water recovered from the heavy water reactor unit to confirm that the water quality is up to standard.

[0031] 11. The purified heavy water from the heavy water reactor unit is discharged through the outlet quick connector and stored in the heavy water reactor unit heavy water purification system.

[0032] 12. If the liquid leak detector alarms during the above steps, emergency plugging is required to prevent the heavy water reactor unit from leaking and expanding.

[0033] Furthermore, in step 7, the power of the ultraviolet lamp ensures that the temperature of the recovered heavy water in the heavy water reactor unit does not exceed 55°C.

[0034] Beneficial technical effects of the present invention:

[0035] The heavy water purification system for heavy water reactor unit recovery of the present invention effectively removes ionic impurities, organic matter, and solid particulate matter from the heavy water recovered from the heavy water reactor unit through a combination of a filtration and oil removal subsystem, an ultraviolet oxidation subsystem, and an adsorption and exchange subsystem, without increasing the amount of resin and activated carbon used, thus effectively controlling the amount of radioactive waste generated. Through a negative pressure exhaust subsystem and a monitoring subsystem, it ensures that there will be no leakage of heavy water recovered from the heavy water reactor unit during the production process, and the radioactive containment effect is good. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the heavy water recovery and purification system for a heavy water reactor unit according to the present invention;

[0037] Figure 2 This is a schematic diagram of the filter structure;

[0038] Figure 3 This is a schematic diagram of the filter element structure;

[0039] Figure 4 This is a top view of the filter element;

[0040] Figure 5 This is a magnified view of a portion of the UV oxidation water tank.

[0041] In the diagram: 1. Inlet quick connector; 2. Filter; 3. UV oxidation water tank; 4. UV lamp tube; 5. Quartz protective sleeve; 6. Dosing funnel; 7. Inspection manhole flange cover; 8. Activated carbon bed; 9. Ion exchange resin bed; 10. Exhaust fan; 11. Molecular sieve adsorption bed; 12. Reflux valve; 13. Circulation pump; 14. Liquid sampler; 15. Liquid leak detector; 16. Radioactivity monitor; 17. Micro pressure gauge; 18. Outlet quick connector; 19. Exhaust duct of plant ventilation system; 20. PTFE gasket; 21. Silicone sealing plug; 22. Silicone sealing gasket; 23. Cable; 24. Fixing screw; 25. Water inlet; 26. Water outlet; 27. Stainless steel frame; 28. Multi-layer oil filter paper; 29. ​​Stainless steel filter screen. Detailed Implementation

[0042] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] See Figure 1 This embodiment provides a heavy water recovery and purification system for a heavy water reactor unit, including an ultraviolet oxidation subsystem, a pressure-sealed filtration and oil removal subsystem, an adsorption exchange subsystem, and a negative pressure exhaust filtration subsystem, a monitoring subsystem, a circulating pump 13, and a control subsystem. The filtration and oil removal subsystem is connected to the pipelines of the ultraviolet oxidation subsystem and the adsorption exchange subsystem, respectively. The inlet of the circulating pump 13 is connected to the pipelines of the filtration and oil removal subsystem and the ultraviolet oxidation subsystem, respectively. The outlet of the circulating pump 13 is connected to the pipelines of the ultraviolet oxidation subsystem and the adsorption exchange subsystem, respectively. The negative pressure exhaust filtration subsystem is connected to the pipeline of the ultraviolet oxidation subsystem. The monitoring subsystem monitors gas and liquid leaks in the heavy water recovery and purification system of the heavy water reactor unit. The control subsystem controls the start and stop of the circulating pump 13, the ultraviolet oxidation subsystem, and the negative pressure exhaust filtration subsystem.

[0044] In this embodiment, the filtration and oil removal subsystem includes a filter 2, an inlet pipe, and an outlet pipe; the filter 2 includes a pressure-bearing sealed housing and a filter element that is detachably fixed inside the pressure-bearing sealed housing; the pressure-bearing sealed housing is provided with an inlet 25 and an outlet 26, the inlet 25 is connected to the inlet pipe, the outlet 26 is connected to the outlet pipe, and valves are provided on both the inlet pipe and the outlet pipe.

[0045] In this embodiment, the filter element consists of a stainless steel frame 27, multiple layers of oil filter paper 28, and a stainless steel filter screen 29 that are wrapped from the inside out. The filter element is detachably fixed in the pressure-bearing sealing housing by means of a fixing screw 24 that passes through the stainless steel frame 27 and is threaded to the bottom of the pressure-bearing sealing housing.

[0046] The heavy water recovered by the heavy water reactor unit is transported through the heavy water recovery pipeline of the heavy water reactor unit. The heavy water recovery pipeline of the heavy water reactor unit is connected to the inlet pipeline through the inlet quick connector 1. The heavy water recovered by the heavy water reactor unit enters the pressure-bearing sealed shell through the inlet 25, passes through the stainless steel filter screen 29, the multi-layer oil filter paper 28 and the stainless steel skeleton 27 in sequence, and enters the outlet pipeline through the outlet 26.

[0047] In this embodiment, the stainless steel filter screen 29 is a 150μm stainless steel filter screen, which filters out solid particles such as resin, activated carbon, molecular sieve debris, dust, and metal debris larger than 150μm; the multi-layer oil filter paper 28 is a corrugated multi-layer oil filter paper, which increases the filtration area and filters out most of the lubricating oil contaminants from mechanical equipment.

[0048] In this embodiment, the ultraviolet oxidation subsystem includes an ultraviolet oxidation water tank 3, an ultraviolet lamp tube 4, a quartz protective sleeve 5, a dosing funnel 6, and a maintenance manhole flange cover 7. The top of the ultraviolet oxidation water tank 3 is threadedly sealed to the maintenance manhole flange cover 7. The maintenance manhole flange cover 7 has evenly distributed holes for placing the quartz protective sleeve 5, and the ultraviolet lamp tube 4 is placed inside the quartz protective sleeve 5. The opening of the quartz protective sleeve 5 is sealed and fixed by a silicone sealing ring 21. The cable 23 of the ultraviolet lamp tube 4 passes through the silicone sealing ring 21 and is connected to an external power supply circuit. The quartz protective sleeve 5 and the holes on the maintenance manhole flange cover 7 are sealed with silicone. Gasket 22 is used for sealing and fixing; the dosing funnel 6 is connected to the ultraviolet oxidation water tank 3 via pipeline and is used to add hydrogen peroxide to the ultraviolet oxidation water tank 3 to enhance the oxidation capacity of ultraviolet light; a valve is provided on the pipeline connecting the dosing funnel 6 and the ultraviolet oxidation water tank 3; the inlet of the circulating pump 13 is connected to the outlet of the ultraviolet oxidation water tank 3 and the outlet pipeline respectively, the outlet of the circulating pump 13 is connected to the inlet pipeline of the ultraviolet oxidation water tank 3, a valve is provided on the pipeline connecting the inlet of the circulating pump 13 and the outlet of the ultraviolet oxidation water tank 3, and a liquid sampler 14 and a valve are provided on the pipeline connecting the outlet of the circulating pump 13 and the inlet of the ultraviolet oxidation water tank 3. The liquid sampler 14 is used for manual water sampling.

[0049] By irradiating the heavy water with ultraviolet light of a specific wavelength and power and adding a certain concentration of hydrogen peroxide, hydroxyl radicals HO· are generated in the heavy water recovered from the heavy water reactor unit.

[0050] H₂O₂ + UV → 2HO·

[0051] Hydroxyl radicals are currently the most powerful oxidizing agents, and they are also strong oxidants with no obvious selectivity for various organic pollutants. Hydroxyl radicals can undergo rapid chain reactions with organic pollutants in the heavy water recovered from heavy water reactors without selectivity, breaking down the chains and decomposing recalcitrant organic compounds such as chloroform, trichloromethane, trichloroethane, and urea in the recovered heavy water into CO2 and H2O, as well as F-, Cl-, NO3-, and SO4, which are easily removed by activated carbon and ion exchange resins. 2 - Plasma impurities.

[0052] The production process does not generate chemical pollution. The organic matter in the recovered heavy water and the carbon, hydrogen and oxygen elements in the added hydrogen peroxide are basically converted into water and carbon dioxide, without increasing the amount of resin and activated carbon used. The production process has zero discharge and does not generate radioactive waste liquid, effectively controlling the amount of radioactive waste and radioactive waste liquid.

[0053] In this embodiment, the adsorption exchange subsystem includes an ion exchange resin bed 9 and an activated carbon bed 8; the outlet of the circulating pump 13 is also connected to the inlet pipe of the activated carbon bed 8, the outlet of the activated carbon bed 8 is connected to the inlet pipe of the ion exchange resin bed 9, the outlet of the ion exchange resin bed 9 is connected to the inlet pipe of the ultraviolet oxidation water tank 3, the liquid sampler 14 is connected to the pipes connecting the outlet of the ion exchange resin bed 9 to the inlet of the ultraviolet oxidation water tank 3 and the pipes connecting the outlet of the circulating pump 13 to the inlet of the ultraviolet oxidation water tank 3, and a three-way valve is provided on the pipes connecting the outlet of the circulating pump 13 to the inlet of the ultraviolet oxidation water tank 3 and the inlet of the activated carbon bed 8.

[0054] In this embodiment, the circulation pump 13 is a sealed magnetic pump to prevent leakage of heavy water recovered from the heavy water reactor unit. The circulation pump 13 provides flow rates for transfer, circulation purification, and sampling.

[0055] In this embodiment, the ion exchange resin bed 9 is filled with nuclear-grade uniform-particle gel-type mixed resin. The nuclear-grade uniform-particle gel-type mixed resin is composed of nuclear-grade uniform-particle gel-type H-type strong acid cation resin and OH-type strong base anion resin in a 1:1 stoichiometric ratio. The heavy water reactor unit, which purifies water to a neutral state, recovers ionic impurities such as chloride ions, lithium ions, carbonates, and metal ions, as well as radioactive waste such as I-131, Co-60, and Zn-65 from the heavy water.

[0056] The activated carbon bed 8 further absorbs residual lubricating oil contaminants, solid particles such as resin, activated carbon, molecular sieve debris, dust, and metal shavings smaller than 150μm, as well as organic matter such as methane, ethane, ethanol, and acetic acid.

[0057] In this embodiment, the negative pressure exhaust filtration subsystem includes an exhaust fan 10 and a molecular sieve adsorption bed 11; the air space of the ultraviolet oxidation water tank 3 is sequentially connected to the inlet pipes of the molecular sieve adsorption bed 11 and the exhaust fan 10, the outlet of the exhaust fan 10 is connected to the air space of the ultraviolet oxidation water tank 3 and the exhaust pipe 19 of the factory ventilation system, and a reflux valve 12 is provided on the pipe connecting the outlet of the exhaust fan 10 to the air space of the ultraviolet oxidation water tank 3.

[0058] The exhaust fan 10 provides a slight negative pressure of -20Pa to -30Pa to the gas space of the ultraviolet oxidation water tank 3 to balance the pressure changes in the gas space of the ultraviolet oxidation water tank 3 caused by changes in the filling volume and temperature of the ultraviolet oxidation water tank 3, and to prevent leakage of heavy water vapor recovered by the heavy water reactor unit in the ultraviolet oxidation water tank 3.

[0059] The molecular sieve adsorption bed 11 can adsorb 99.9% of the heavy water vapor in the gas emitted from the ultraviolet oxidation water tank 3, preventing the emission of radioactive tritium.

[0060] In this embodiment, the monitoring subsystem includes a liquid leak detector 15. A stainless steel water receiving tray is installed at the bottom of the heavy water reactor unit's heavy water recovery and purification system. The liquid leak detector 15 is mounted on the lowest point of the stainless steel water receiving tray via a base. The liquid leak detector 15 includes a probe, and the base and the probe are a pair of electrodes with a gap between them. When there is leaking water at the lowest point of the stainless steel water receiving tray and the water level rises to the probe position, the two electrodes conduct and generate an alarm.

[0061] In this embodiment, the monitoring subsystem further includes a radioactivity monitor 16 installed on the pipeline connecting the outlet of the exhaust fan 10 to the exhaust pipe 19 of the factory ventilation system; the radioactivity monitor 16 monitors the radioactivity tritium activity of the gas at the outlet of the exhaust fan 10; when the radioactivity tritium activity of the gas at the outlet of the exhaust fan 10 exceeds the warning value, the radioactivity monitor 16 issues an alarm.

[0062] In this embodiment, the monitoring subsystem further includes a micro pressure gauge 17 installed on the top of the ultraviolet oxidation water tank 3 for monitoring the air space pressure of the ultraviolet oxidation water tank 3.

[0063] To ensure the system's containment of radioactive gases, a liquid leak detector 15 is used to detect heavy water leaks; a micro-pressure gauge 17 is used to monitor the pressure in the ultraviolet oxidation water tank to ensure that radioactive gases do not diffuse outwards even if the seal is not tight; and a radioactivity monitor 16 is used to monitor the radioactive tritium activity in the exhaust gas from the exhaust fan 10 to reflect the adsorption effect of the molecular sieve adsorption bed 11 on heavy water vapor.

[0064] In this embodiment, the control subsystem controls the start and stop of the circulating pump 13, the ultraviolet lamp 4, and the exhaust fan 10.

[0065] The process of using the aforementioned heavy water recovery and purification system for heavy water reactor units includes the following steps:

[0066] 1. Start the exhaust fan 10 of the negative pressure exhaust filtration subsystem to establish a micro negative pressure of -20Pa to -30Pa in the air space of the ultraviolet oxidation water tank 3;

[0067] 2. Start the circulation pump 13 to pump the heavy water recovered from the heavy water reactor unit into the heavy water recovery purification system through the inlet quick connector 1;

[0068] 3. The heavy water recovered from the heavy water reactor unit flows through filter 2 to remove most of the solid particles and grease;

[0069] 4. The heavy water reactor unit recovers heavy water and enters the ultraviolet oxidation water tank 3. After stopping the circulation pump 13 and controlling the ultraviolet oxidation water tank 3 to reach an appropriate liquid level, the water intake of the ultraviolet oxidation water tank 3 is stopped. The liquid level of the ultraviolet oxidation water tank 3 should not exceed the opening of the dosing funnel 6 to avoid the hydrogen peroxide being added uncontrollably.

[0070] 5. The heavy water recovered from the heavy water reactor unit in the ultraviolet oxidation water tank 3 is circulated, and samples are taken through the liquid sampler 14 to determine the initial TOC concentration of the heavy water recovered from the heavy water reactor unit.

[0071] 6. Determine the amount of hydrogen peroxide to be added based on the initial TOC concentration of the heavy water recovered by the heavy water reactor unit. Generally, the hydrogen peroxide concentration should be controlled to be 6 times the initial TOC concentration of the heavy water recovered by the heavy water reactor unit.

[0072] 7. Turn on the ultraviolet lamp 4, add sufficient hydrogen peroxide through the dosing funnel 6, and keep the ultraviolet oxidation water tank 3 in self-circulation;

[0073] 8. Periodically take samples through liquid sampler 14 to analyze the hydrogen peroxide concentration in the heavy water recovered by the heavy water reactor unit in the ultraviolet oxidation water tank 3 until the hydrogen peroxide concentration is less than 2 mg / kg.

[0074] 9. The heavy water recovered from the heavy water reactor unit in the ultraviolet oxidation water tank 3 is input into the adsorption exchange subsystem, and then returns to the ultraviolet oxidation water tank 3 after passing through the activated carbon bed 8 and the ion exchange resin bed 9 in sequence.

[0075] 10. Samples were taken using liquid sampler 14, and various purification indicators of the heavy water recovered from the heavy water reactor unit were measured to confirm that the water quality was up to standard.

[0076] 11 The purified heavy water from the heavy water reactor unit is discharged from the heavy water reactor unit's heavy water purification system via the outlet quick connector 18 for storage.

[0077] 12. If the liquid leak detector 15 alarms during the above steps, emergency plugging is required to prevent the heavy water reactor unit from leaking and expanding.

[0078] In step 1, the molecular sieve adsorption bed 11 can adsorb 99.9% of the heavy water vapor in the gas emitted from the ultraviolet oxidation water tank 3; the radioactivity monitoring instrument 16 monitors the radioactivity tritium activity of the gas at the outlet of the exhaust fan 10; when the radioactivity tritium activity of the gas at the outlet of the exhaust fan 10 exceeds the warning value, the radioactivity monitoring instrument 16 issues an alarm, reminding personnel to manually operate or automatically control the molecular sieve adsorption bed 11 through PLC to perform high-temperature regeneration; the high-temperature regeneration of the molecular sieve adsorption bed 11 includes the following steps: the air inside the molecular sieve adsorption bed 11... The air is circulated, and the moisture inside the molecular sieve adsorption bed 11 is carried out by the electric heater. The moisture is then condensed by the condenser and collected and returned to the ultraviolet oxidation water tank 3. The pressure of the ultraviolet oxidation water tank 3 gas space is adjusted to -20Pa to -30Pa through the return valve 12 installed on the pipeline connecting the outlet of the exhaust fan 10 to the gas space of the ultraviolet oxidation water tank 3. The outlet of the exhaust fan 10 is connected to the pipeline of the ultraviolet oxidation water tank 3 gas space to prevent the exhaust fan 10 from stalling due to lack of medium. The pressure of the ultraviolet oxidation water tank 3 gas space is monitored by the micro pressure gauge 17.

[0079] In step 5, the concentration of hydrogen peroxide added should be adapted to the initial TOC level of the heavy water recovered by the heavy water reactor unit. If the concentration of hydrogen peroxide added is too low, it needs to be added repeatedly, prolonging the working time of the heavy water recovery and purification system of the heavy water reactor unit. If the concentration of hydrogen peroxide added is too high, the organic matter in the heavy water recovered by the heavy water reactor unit will be completely removed, but a certain concentration of hydrogen peroxide will remain. When water with residual hydrogen peroxide enters the activated carbon bed and resin bed, it will cause a certain degree of pulverization of activated carbon and premature saturation of resin. According to experiments, the optimal concentration of hydrogen peroxide added is 6 times the initial TOC concentration of the heavy water recovered by the heavy water reactor unit.

[0080] In step 7, ultraviolet oxidation typically uses wavelengths of 185nm and / or 254nm. 185nm ultraviolet light has a shorter wavelength and higher energy, with a photon energy equivalent to 6.7eV, while 254nm ultraviolet light has an energy equivalent to 4.88eV. Theoretically, the higher the power of the ultraviolet light and the higher the concentration of hydrogen peroxide, the better the effect on degrading organic matter. In practical applications, during operation, the light energy of the ultraviolet lamp is converted into heat energy, raising the temperature of the working medium. Excessive medium temperature (>55℃) can damage the resin, causing it to lose its exchange capacity, and ions already attached to the resin may be released, or even the resin may break down, leading to water quality deterioration. Therefore, the power of the ultraviolet lamp should be limited based on the heat dissipation coefficient of the materials during system operation to ensure that the medium temperature does not exceed 55℃.

[0081] After the heavy water recovery purification system provided in this embodiment is used to purify the heavy water recovered from the heavy water reactor unit, the purpose of effectively removing ionic impurities, organic matter and solid particulate matter from the heavy water recovered from the heavy water reactor unit is achieved. The various indicators of the purified heavy water recovered from the heavy water reactor unit are shown in Table 1.

[0082] Table 1. Indicators of heavy water recovered from the purified heavy water reactor unit

[0083] Analysis parameters Required indicators Actual measurement results TOC <3mg / kg 1.08 mg / kg F <100μg / kg 0.81 μg / kg B <1mg / kg <0.01mg / kg Cl <100μg / kg 1.56 μg / kg pH 6～8 6.5 electrical conductivity <2μS / cm 1.18 μS / cm Gd <50μg / kg <5μg / kg <![CDATA[NH3]]> <100μg / kg <0.10μg / kg <![CDATA[NO3]]> <100μg / kg 3.18 μg / kg <![CDATA[SO4]]> <100μg / kg <1.0μg / kg suspended matter <0.1mg / kg <0.05mg / kg

[0084] 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 heavy water reactor unit heavy water recovery and purification system, characterized in that, It includes an ultraviolet oxidation subsystem, a pressure-sealed filtration and oil removal subsystem, an adsorption exchange subsystem and a negative pressure exhaust filtration subsystem, a monitoring subsystem, a circulating pump (13), and a control subsystem; The oil removal filtration subsystem is connected to the pipelines of the ultraviolet oxidation subsystem and the adsorption exchange subsystem respectively. The inlet of the circulating pump (13) is connected to the pipelines of the oil removal filtration subsystem and the ultraviolet oxidation subsystem respectively. The outlet of the circulating pump (13) is connected to the pipelines of the ultraviolet oxidation subsystem and the adsorption exchange subsystem respectively. The negative pressure exhaust filtration subsystem is connected to the pipeline of the ultraviolet oxidation subsystem. The monitoring subsystem monitors the gas leakage and liquid leakage in the heavy water purification system of the heavy water reactor unit. The control subsystem controls the start and stop of the circulating pump (13), the ultraviolet oxidation subsystem and the negative pressure exhaust filtration subsystem. The ultraviolet oxidation subsystem includes an ultraviolet oxidation water tank (3), and a liquid sampler (14) is provided on the pipeline connecting the outlet of the circulating pump (13) and the inlet of the ultraviolet oxidation water tank (3). The adsorption exchange subsystem includes an ion exchange resin bed (9) and an activated carbon bed (8); the outlet of the circulating pump (13) is also connected to the inlet pipe of the activated carbon bed (8), the outlet of the activated carbon bed (8) is connected to the inlet pipe of the ion exchange resin bed (9), the outlet of the ion exchange resin bed (9) is connected to the inlet pipe of the ultraviolet oxidation water tank (3), the liquid sampler (14) is connected to the pipes connecting the outlet of the ion exchange resin bed (9) and the inlet of the ultraviolet oxidation water tank (3) and the outlet of the circulating pump (13) and the inlet of the ultraviolet oxidation water tank (3), respectively, and a three-way valve is provided on the pipes connecting the outlet of the circulating pump (13) to the inlet of the ultraviolet oxidation water tank (3) and the inlet of the activated carbon bed (8).

2. The heavy water recovery and purification system for a heavy water reactor unit according to claim 1, characterized in that, The filtration and oil removal subsystem includes a filter (2), an inlet pipe, and an outlet pipe; the filter (2) includes a pressure-bearing sealed housing and a filter element that is detachably fixed inside the pressure-bearing sealed housing; the pressure-bearing sealed housing is provided with an inlet (25) and an outlet (26), the inlet (25) is connected to the inlet pipe, the outlet (26) is connected to the outlet pipe, and valves are provided on both the inlet pipe and the outlet pipe.

3. The heavy water recovery and purification system for a heavy water reactor unit according to claim 2, characterized in that, The filter element consists of a stainless steel frame (27) covering the inside from the outside, multiple layers of oil filter paper (28) and stainless steel filter screen (29). The filter element is detachably fixed in the pressure-bearing sealed housing by a fixing screw (24) passing through the stainless steel frame (27) and threadedly connected to the bottom of the pressure-bearing sealed housing.

4. The heavy water recovery and purification system for a heavy water reactor unit according to claim 3, characterized in that, The stainless steel filter screen (29) is a 150μm stainless steel filter screen; the multi-layer oil filter paper (28) is a corrugated multi-layer oil filter paper.

5. The heavy water recovery and purification system for a heavy water reactor unit according to claim 2, characterized in that, The ultraviolet oxidation subsystem also includes an ultraviolet lamp tube (4), a quartz protective sleeve (5), a dosing funnel (6), and a maintenance manhole flange cover (7); the top of the ultraviolet oxidation water tank (3) is threadedly sealed to the maintenance manhole flange cover (7); the maintenance manhole flange cover (7) has evenly distributed holes for placing the quartz protective sleeve (5), and the ultraviolet lamp tube (4) is placed inside the quartz protective sleeve (5); the opening of the quartz protective sleeve (5) is sealed and fixed by a silicone sealing ring (21); the cable (23) of the ultraviolet lamp tube (4) passes through the silicone sealing ring (21) and is connected to an external power supply circuit; there is a connection between the quartz protective sleeve (5) and the holes on the maintenance manhole flange cover (7). The device is sealed and fixed by a silicone sealing gasket (22); the dosing funnel (6) is connected to the ultraviolet oxidation water tank (3) by a pipeline and is used to add hydrogen peroxide into the ultraviolet oxidation water tank (3); a valve is provided on the pipeline connecting the dosing funnel (6) and the ultraviolet oxidation water tank (3); the inlet of the circulating pump (13) is connected to the outlet of the ultraviolet oxidation water tank (3) and the outlet pipeline respectively; the outlet of the circulating pump (13) is connected to the inlet pipeline of the ultraviolet oxidation water tank (3); a valve is provided on the pipeline connecting the inlet of the circulating pump (13) and the outlet of the ultraviolet oxidation water tank (3); a valve is also provided on the pipeline connecting the outlet of the circulating pump (13) and the inlet of the ultraviolet oxidation water tank (3).

6. The heavy water recovery and purification system for a heavy water reactor unit according to claim 1, characterized in that, The circulating pump (13) is a sealed magnetic pump.

7. The heavy water recovery and purification system for a heavy water reactor unit according to claim 1, characterized in that, The ion exchange resin bed (9) is filled with nuclear-grade uniform-particle gel-type mixed resin, which is composed of nuclear-grade uniform-particle gel-type H-type strong acid cation resin and OH-type strong base anion resin in a 1:1 stoichiometric ratio.

8. The heavy water recovery and purification system for a heavy water reactor unit according to claim 1, characterized in that, The negative pressure exhaust filtration subsystem includes an exhaust fan (10) and a molecular sieve adsorption bed (11); the gas space of the ultraviolet oxidation water tank (3) is connected in sequence to the inlet pipes of the molecular sieve adsorption bed (11) and the exhaust fan (10); the outlet of the exhaust fan (10) is connected to the gas space pipe of the ultraviolet oxidation water tank (3); and a reflux valve (12) is provided on the pipe connecting the outlet of the exhaust fan (10) to the gas space of the ultraviolet oxidation water tank (3).

9. The heavy water recovery and purification system for a heavy water reactor unit according to claim 8, characterized in that, The monitoring subsystem includes a liquid leak detector (15), a radioactivity monitor (16), and a micro-pressure gauge (17); a stainless steel water receiving tray is installed at the bottom of the heavy water reactor unit's heavy water recovery and purification system, and the liquid leak detector (15) is installed at the lowest point of the stainless steel water receiving tray via a base; the liquid leak detector (15) includes a probe, the base and the probe are a pair of electrodes, and a gap is left between the probe and the base; when there is leakage water at the lowest point of the stainless steel water receiving tray and the water level rises to the probe... When the position is correct, the two electrodes are connected to generate an alarm; the outlet of the exhaust fan (10) is equipped with a radioactivity monitor (16); the radioactivity monitor (16) monitors the gas radioactivity tritium activity at the outlet of the exhaust fan (10); when the gas radioactivity tritium activity at the outlet of the exhaust fan (10) exceeds the warning value, the radioactivity monitor (16) issues an alarm; the monitoring subsystem also includes a micro pressure gauge (17) installed on the top of the ultraviolet oxidation water tank (3) for monitoring the gas space pressure of the ultraviolet oxidation water tank (3).

10. The heavy water recovery and purification system for a heavy water reactor unit according to claim 9, characterized in that, The control subsystem controls the start and stop of the circulating pump (13), the ultraviolet lamp (4), and the exhaust fan (10).

11. A process for recovering and purifying heavy water in a heavy water reactor unit, characterized in that, The heavy water recovery and purification system for a heavy water reactor unit according to any one of claims 1-10 includes the following steps: 1) Start the exhaust fan (10) of the negative pressure exhaust filtration subsystem to establish a micro negative pressure of -20Pa to -30Pa in the air space of the ultraviolet oxidation water tank (3); 2) Start the circulating pump (13) to pump the heavy water recovered from the heavy water reactor unit into the heavy water recovery purification system through the inlet quick connector (1); 3) The heavy water recovered by the heavy water reactor unit flows through the filter (2) to remove most of the solid particles and grease; 4) The heavy water reactor unit recovers heavy water and enters the ultraviolet oxidation water tank (3). The circulating pump (13) is stopped and the water level in the ultraviolet oxidation water tank (3) is controlled to be no more than the opening of the dosing funnel (6) before the water inlet of the ultraviolet oxidation water tank (3) is stopped. 5) The heavy water recovered from the heavy water reactor unit in the ultraviolet oxidation water tank (3) is circulated, and samples are taken by liquid sampler (14) to determine the initial TOC concentration of the heavy water recovered from the heavy water reactor unit. 6) The amount of hydrogen peroxide to be added should be 6 times the initial TOC concentration of the heavy water recovered by the heavy water reactor unit. 7) Turn on the ultraviolet lamp (4), add sufficient hydrogen peroxide through the dosing funnel (6), and keep the ultraviolet oxidation water tank (3) in self-circulation; 8) Periodically sample and analyze the hydrogen peroxide concentration of the heavy water recovered by the heavy water reactor unit in the ultraviolet oxidation water tank (3) until the hydrogen peroxide concentration is less than 2 mg / kg; 9) The heavy water recovered from the heavy water reactor unit in the ultraviolet oxidation water tank (3) is input into the adsorption exchange subsystem, and then returns to the ultraviolet oxidation water tank (3) after passing through the activated carbon bed (8) and the ion exchange resin bed (9) in sequence. 10) Take samples using a liquid sampler (14) and measure various purification indicators of the heavy water recovered by the heavy water reactor unit to confirm that the water quality is qualified; 11) The purified heavy water recovered from the heavy water reactor unit is sent out through the outlet quick connector (18) to the heavy water recovery purification system of the heavy water reactor unit for storage; 12) If the liquid leak detector (15) alarms during the above steps, emergency plugging is required to prevent the heavy water reactor unit from leaking and expanding.

12. The heavy water recovery and purification process for heavy water reactor units according to claim 11, characterized in that, In step 7), the power of the ultraviolet lamp (4) ensures that the temperature of the recovered heavy water in the heavy water reactor unit does not exceed 55°C.

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