Recovered heavy water purification system of heavy water reactor unit

Abstract

The invention particularly relates to a heavy water reactor unit recovered heavy water purification system which comprises an ultraviolet oxidation subsystem, an adsorption exchange subsystem, a circulating pump, a filtering oil removal subsystem in pipeline connection with the ultraviolet oxidation subsystem and the adsorption exchange subsystem, and a negative pressure exhaust filtering subsystem in pipeline connection with the ultraviolet oxidation subsystem. The monitoring subsystem is used for monitoring leakage of recovered heavy water of the heavy water reactor unit; the control subsystem is used for controlling start and stop of a circulating pump, the ultraviolet oxidation subsystem and the negative pressure exhaust filtering subsystem; a water inlet of the circulating pump is respectively connected with the filtering oil removal subsystem and the ultraviolet oxidation subsystem through pipelines, and a water outlet of the circulating pump is respectively connected with the ultraviolet oxidation subsystem and the adsorption exchange subsystem through pipelines. The recovery heavy water purification system of the heavy water reactor unit effectively removes ion impurities, organic matters and solid particles on the premise of preventing diffusion of radioactive substances and avoiding additional increase of radioactive wastes.

Description

Technical Field

[0001] The invention relates to the technical field of heavy water recovery and treatment of heavy water from a heavy water reactor unit, and in particular to a heavy water recovery and purification system for a heavy water reactor unit. Background Art

[0002] Heavy water reactors use heavy water as a moderator and coolant. Heavy water is an important nuclear material. Its content in natural water is only 0.015%, and the cost of preparation and purification is very high. During the operation of the heavy water reactor, some deuterium in the heavy water will absorb neutrons and become tritium. With the continuous operation of the heavy water reactor, the concentration of tritium in the moderator and coolant continues to accumulate and increase. Tritium is radioactive and will undergo β decay. When the human body ingests tritium, it will cause long-term internal radiation. Therefore, during the operation of the heavy water reactor, heavy water in the gaseous and liquid forms in the plant environment must be recovered as much as possible to save the cost of heavy water and limit the spread of tritium. The recovered heavy water usually contains a variety of pollutants such as ionic impurities, organic matter, and solid particles. It needs to be purified to meet the corresponding indicators before it can be reused.

[0003] At present, heavy water reactor units mostly use ion exchange resins and activated carbon to purify recycled heavy water. Although ion exchange resins can remove ionic impurities, they have little effect on the treatment of organic matter. Activated carbon has a weak adsorption capacity for organic matter in recycled heavy water, and the difficult-to-degrade organic matter in heavy water cannot be removed. The treatment process for organic matter in traditional water treatment processes lacks the design of containing radioactive waste and controlling the amount of radioactive waste, and cannot be directly applied to the purification of recycled heavy water in heavy water reactor units. For example, reverse osmosis technology will produce a certain proportion of sewage discharge; ultraviolet synergistic oxidation technology lacks closed radioactive containment measures; chemical oxidation methods will increase the amount of resin and activated carbon used, and produce more radioactive waste.

[0004] Therefore, a heavy water reactor unit heavy water recovery and purification system and process are needed, which can effectively remove ionic impurities, organic matter and solid particles in tritium-containing heavy water while preventing the spread of radioactivity and avoiding additional radioactive waste, so that the purified recovered heavy water can meet the heavy water demand of the heavy water reactor. Summary of the invention

[0005] The object of the present invention is to provide a heavy water reactor unit recovery heavy water purification system, which effectively removes ionic impurities, organic matter and solid particles in the heavy water recovered by the heavy water reactor unit under the premise of preventing the spread of radioactive waste and avoiding additional increase of radioactive waste, so that the purified recovered heavy water can meet the heavy water demand of the heavy water reactor unit.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A heavy water recovery purification system for a heavy water reactor unit comprises an ultraviolet oxidation subsystem, a filtering and degreasing subsystem with a pressure-bearing and sealing structure, an adsorption exchange subsystem and a negative pressure exhaust filtration subsystem, a monitoring subsystem, a circulation pump, and a control subsystem; the filtering and degreasing subsystem is respectively connected to the ultraviolet oxidation subsystem and the adsorption exchange subsystem pipelines, the water inlet of the circulation pump is respectively connected to the filtering and degreasing subsystem and the ultraviolet oxidation subsystem pipelines, the water outlet of the circulation pump is respectively connected to the ultraviolet oxidation subsystem and the adsorption exchange subsystem pipelines, the negative pressure exhaust filtration subsystem is connected to the ultraviolet oxidation subsystem pipeline, the monitoring subsystem monitors gas leakage and liquid leakage in the heavy water recovery purification system for the heavy water reactor unit, and the control subsystem controls the start and stop of the circulation pump, the ultraviolet oxidation subsystem and the negative pressure exhaust filtration subsystem.

[0008] Furthermore, the filtering and oil removal subsystem includes a filter, a water inlet pipe and a water outlet pipe; the filter includes a pressure-bearing sealed shell and a filter element detachably fixed in the pressure-bearing sealed shell; the pressure-bearing sealed shell is provided with a water inlet and a water outlet, the water inlet is connected to the water inlet pipe, the water outlet is connected to the water outlet pipe, and valves are provided on the water inlet pipe and the water outlet pipe.

[0009] Furthermore, the filter element is composed of a stainless steel frame, multiple layers of oil filter paper and a stainless steel filter screen wrapped from the inside to the outside. The filter element is detachably fixed in the pressure-bearing sealing shell by fixing screws passing through the stainless steel frame and connected to the bottom thread of the pressure-bearing sealing shell.

[0010] Furthermore, the stainless steel filter is a 150 μm stainless steel filter; and 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 an inspection manhole flange cover; the top of the ultraviolet oxidation water tank is threaded and sealed to connect to the inspection manhole flange cover; the inspection manhole flange cover is provided with evenly distributed holes for placing the quartz protective sleeve, and the ultraviolet lamp tube is placed in the quartz protective sleeve; 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 the external power supply circuit; the quartz protective sleeve and the holes on the inspection manhole flange cover are connected by The silicone sealing pad is sealed and fixed; 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 water inlet of the circulating pump is respectively connected to the water outlet and the outlet pipeline of the ultraviolet oxidation water tank, the water outlet of the circulating pump is connected to the water inlet pipeline of the ultraviolet oxidation water tank, a valve is provided on the pipeline connecting the water inlet of the circulating pump and the water outlet of the ultraviolet oxidation water tank, and a liquid sampler and a valve are provided on the pipeline connecting the water outlet of the circulating pump and the water 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 water outlet of the circulation pump is also connected to the water inlet pipeline of the activated carbon bed, the water outlet of the activated carbon bed is connected to the water inlet pipeline of the ion exchange resin bed, the water outlet of the ion exchange resin bed is connected to the water inlet pipeline of the ultraviolet oxidation water tank, the liquid sampler is respectively on the pipeline connecting the water outlet of the ion exchange resin bed and the water inlet of the ultraviolet oxidation water tank and the pipeline connecting the water outlet of the circulation pump and the water inlet of the ultraviolet oxidation water tank, and a three-way valve is provided on the pipeline connecting the water outlet of the circulation pump and the water inlet of the ultraviolet oxidation water tank and the water inlet of the activated carbon bed.

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

[0014] Furthermore, the ion exchange resin bed is filled with a core-grade uniform-particle gel-type mixed resin, which is composed of a core-grade uniform-particle gel-type H-type strongly acidic cation resin and an OH-type strongly basic anion resin in a 1:1 stoichiometric equivalent.

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

[0016] Furthermore, the monitoring subsystem includes a liquid leakage detector, a radioactive activity monitor and a micro pressure gauge; a stainless steel water receiving tray is arranged at the bottom of the heavy water recovery purification system of the heavy water reactor unit, and the liquid leakage detector is installed at the lowest point of the stainless steel water receiving tray through a base; the liquid leakage detector 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 water leakage at the lowest point of the stainless steel water receiving tray and the water level rises to the position of the probe, the two electrodes are connected to generate an alarm;

[0017] The outlet of the exhaust fan is provided with a radioactive activity monitor; the radioactive activity monitor monitors the radioactive tritium activity of the gas at the outlet of the exhaust fan; when the radioactive tritium activity of the gas at the outlet of the exhaust fan exceeds the warning value, the radioactive activity monitor sends out an alarm;

[0018] The monitoring subsystem also includes a micro pressure gauge arranged on the top of the ultraviolet oxidation water tank, which is 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 circulation pump, the ultraviolet lamp tube and the exhaust fan.

[0020] The present invention also provides a heavy water reactor unit recovery heavy water purification process, comprising the following steps:

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

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

[0023] 3. Heavy water recycled by heavy water reactor units flows through filters to remove most of the solid particles and grease;

[0024] 4. The heavy water reactor unit recycles heavy water into the ultraviolet oxidation water tank. The circulation pump is stopped to control the liquid level of the ultraviolet oxidation water tank to stop the water inflow to the ultraviolet oxidation water tank after it does not exceed the nozzle of the dosing funnel;

[0025] 5. Circulate the heavy water recovered from the heavy water reactor unit in the ultraviolet oxidation water tank, take samples through the liquid sampler, and measure the initial TOC concentration of the heavy water recovered from the heavy water reactor unit;

[0026] 6. According to the initial TOC concentration of heavy water recovered by the heavy water reactor unit, the amount of hydrogen peroxide to be added is determined to be 6 times the initial TOC concentration of heavy water recovered by the heavy water reactor unit;

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

[0028] 8. Regularly take samples through the liquid sampler to analyze the hydrogen peroxide concentration of 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 input 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 through a liquid sampler and measure various purification indicators of heavy water recovered from the heavy water reactor unit to confirm that the water quality is qualified;

[0031] 11 The qualified heavy water recovered from the heavy water reactor unit is transferred out of the heavy water recovery and purification system of the heavy water reactor unit through the outlet quick connector for storage;

[0032] 12. In the above steps, if the liquid leakage detector sounds an alarm, it is necessary to urgently plug the leak to prevent the leakage of heavy water recovered by the heavy water reactor unit from expanding.

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

[0034] Beneficial technical effects of the present invention:

[0035] The heavy water recovery purification system for a heavy water reactor unit of the present invention effectively removes ionic impurities, organic matter and solid particulate matter in heavy water recovered by the heavy water reactor unit through the combination of a filtering and oil removal subsystem, an ultraviolet oxidation subsystem and an adsorption exchange subsystem, and does not increase the dosage of resin and activated carbon, thereby effectively controlling the amount of radioactive waste generated; through a negative pressure exhaust subsystem and a monitoring subsystem, it is ensured that the heavy water recovered by the heavy water reactor unit will not leak during the production process, and the radioactive containment effect is good. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0038] Figure 3 Schematic diagram of filter element structure;

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

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

[0041] In the figure, 1. inlet quick connector; 2. filter; 3. ultraviolet oxidation water tank; 4. ultraviolet lamp tube; 5. quartz protection sleeve; 6. dosing funnel; 7. maintenance 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. radioactive activity monitor; 17. micro pressure gauge; 18. outlet quick connector; 19. exhaust duct of workshop ventilation system; 20. polytetrafluoroethylene gasket; 21. silicone sealing plug; 22. silicone sealing pad; 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. DETAILED DESCRIPTION

[0042] The technical solution of the present invention is described clearly and completely below in conjunction with the accompanying drawings and specific implementation methods. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] See also Figure 1 The present embodiment provides a heavy water reactor unit heavy water recovery purification system, comprising an ultraviolet oxidation subsystem, a filter and oil removal subsystem with a pressure-bearing sealing structure, an adsorption exchange subsystem and a negative pressure exhaust filtration subsystem, a monitoring subsystem, a circulation pump 13, and a control subsystem; the filter and oil removal subsystem is respectively connected to the ultraviolet oxidation subsystem and the adsorption exchange subsystem pipelines, the water inlet of the circulation pump 13 is respectively connected to the filter and oil removal subsystem and the ultraviolet oxidation subsystem pipelines, the water outlet of the circulation pump 13 is respectively connected to the ultraviolet oxidation subsystem and the adsorption exchange subsystem pipelines, the negative pressure exhaust filtration subsystem is connected to the ultraviolet oxidation subsystem pipeline, the monitoring subsystem monitors gas leakage and liquid leakage in the heavy water reactor unit heavy water recovery purification system, and the control subsystem controls the start and stop of the circulation pump 13, the ultraviolet oxidation subsystem and the negative pressure exhaust filtration subsystem.

[0044] In this embodiment, the filtering and oil removal subsystem includes a filter 2, a water inlet pipe and a water outlet pipe; the filter 2 includes a pressure-bearing sealed shell and a filter element detachably fixed in the pressure-bearing sealed shell; the pressure-bearing sealed shell is provided with a water inlet 25 and a water outlet 26, the water inlet 25 is connected to the water inlet pipe, the water outlet 26 is connected to the water outlet pipe, and valves are provided on the water inlet pipe and the water outlet pipe.

[0045] In this embodiment, the filter element is composed of a stainless steel frame 27, multiple layers of oil filter paper 28 and a stainless steel filter screen 29 wrapped from the inside to the outside. The filter element is detachably fixed in the pressure-bearing sealing shell by a fixing screw 24 passing through the stainless steel frame 27 and connected to the bottom thread inside the pressure-bearing sealing shell.

[0046] The heavy water recovered by the heavy water reactor unit is transmitted through the heavy water reactor unit recovery heavy water pipeline, which is connected to the water 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 water 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 water outlet pipeline through the water outlet 26.

[0047] In this embodiment, the stainless steel filter 29 is a 150μm stainless steel filter, which filters out solid particles such as resin, activated carbon, molecular sieve debris, dust, metal debris, etc. with a size 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 pollutants 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 an inspection manhole flange cover 7; the top of the ultraviolet oxidation water tank 3 is threaded and sealed to connect the inspection manhole flange cover 7; the inspection manhole flange cover 7 is provided with evenly distributed holes for placing the quartz protective sleeve 5, and the ultraviolet lamp tube 4 is placed in the quartz protective sleeve 5; 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 the external power supply circuit; the quartz protective sleeve 5 and the holes on the inspection manhole flange cover 7 are sealed by a silicone seal. The gasket 22 is sealed and fixed; the dosing funnel 6 is connected to the ultraviolet oxidation water tank 3 pipeline, and is used to add hydrogen peroxide into the ultraviolet oxidation water tank 3 to enhance the oxidation ability of ultraviolet light; a valve is provided on the pipeline connecting the dosing funnel 6 and the ultraviolet oxidation water tank 3; the water inlet of the circulation pump 13 is respectively connected to the water outlet and the water outlet pipeline of the ultraviolet oxidation water tank 3, the water outlet of the circulation pump 13 is connected to the water inlet pipeline of the ultraviolet oxidation water tank 3, a valve is provided on the pipeline connecting the water inlet of the circulation pump 13 and the water outlet of the ultraviolet oxidation water tank 3, and a liquid sampler 14 and a valve are provided on the pipeline connecting the water outlet of the circulation pump 13 and the water inlet of the ultraviolet oxidation water tank 3. The liquid sampler 14 is used for manual sampling of water quality.

[0049] By irradiating ultraviolet light of a certain 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 free radicals have the strongest oxidizing ability among the current oxidants. At the same time, they are also a strong oxidant with no obvious selectivity for various organic pollutants. Hydroxyl free radicals can react rapidly with organic pollutants in heavy water recovered from heavy water reactor units without selection, destroying the chain and decomposing the refractory organic matter such as chloroform, chloroform, trichloroethane and urea in heavy water recovered from heavy water reactor units into CO2 and H2O, as well as F-, Cl-, NO3- and SO4 that are easily removed by activated carbon and ion exchange resins. 2 - Plasma impurities.

[0052] No chemical pollution will be generated during the production process. The organic matter in the heavy water recovered by the heavy water reactor unit 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. The production process has zero pollution 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 water outlet of the circulating pump 13 is also connected to the water inlet pipeline of the activated carbon bed 8, the water outlet of the activated carbon bed 8 is connected to the water inlet pipeline of the ion exchange resin bed 9, the water outlet of the ion exchange resin bed 9 is connected to the water inlet pipeline of the ultraviolet oxidation water tank 3, the liquid sampler 14 is respectively on the pipeline connecting the water outlet of the ion exchange resin bed 9 and the water inlet of the ultraviolet oxidation water tank 3 and the pipeline connecting the water outlet of the circulating pump 13 and the water inlet of the ultraviolet oxidation water tank 3, and a three-way valve is provided on the pipeline connecting the water outlet of the circulating pump 13 and the water inlet of the ultraviolet oxidation water tank 3 and the water 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 by the heavy water reactor unit. The circulation pump 13 provides flow for transmission, circulation purification and sampling.

[0055] In this embodiment, the ion exchange resin bed 9 is loaded with a nuclear-grade uniform-particle gel-type mixed resin, which is composed of a nuclear-grade uniform-particle gel-type H-type strongly acidic cation resin and an OH-type strongly alkaline anion resin in a 1:1 stoichiometric equivalent, and is used to purify a heavy water reactor unit with neutral water quality to recover ionic impurities such as chloride ions, lithium ions, carbonates and metal ions in heavy water, as well as radioactive wastes such as I-131, Co-60 and Zn-65.

[0056] The activated carbon bed 8 further absorbs residual lubricating oil pollutants, solid particles such as resins below 150 μm, activated carbon, molecular sieve debris, dust, metal debris, and 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 connected to the molecular sieve adsorption bed 11 and the inlet pipeline of the exhaust fan 10 in sequence, and the outlet of the exhaust fan 10 is respectively 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 pipeline connecting the outlet of the exhaust fan 10 and the air space of the ultraviolet oxidation water tank 3.

[0058] The exhaust fan 10 provides a slight negative pressure of -20Pa to -30Pa for the air space of the ultraviolet oxidation water tank 3 to balance the pressure change of the air space of the ultraviolet oxidation water tank 3 caused by the filling amount and temperature change of the ultraviolet oxidation water tank 3, and prevents the 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 exhaust gas of the air space of the ultraviolet oxidation water tank 3, and prevent the emission of radioactive tritium.

[0060] In this embodiment, the monitoring subsystem includes a liquid leakage detector 15. A stainless steel water receiving tray is arranged at the bottom of the heavy water recovery and purification system of the heavy water reactor unit. The liquid leakage detector 15 is installed at the lowest point of the stainless steel water receiving tray through a base. The liquid leakage detector 15 includes a probe. The base and the probe are a pair of electrodes. A gap is left between the probe and the base. When there is water leakage at the lowest point of the stainless steel water receiving tray and the water level rises to the position of the probe, the two electrodes are connected and an alarm is generated.

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

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

[0063] In order to ensure the system's tolerance to radioactive gases, heavy water leakage is detected by a liquid leakage detector 15; the air pressure in the ultraviolet oxidation water tank is monitored by a micro-pressure gauge 17 to be a slightly negative pressure to ensure that the radioactive gas does not diffuse outward when the seal is not tight; the radioactive tritium activity of the exhaust fan 10 is monitored by a radioactive activity monitor 16 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 circulation pump 13 , the ultraviolet lamp 4 and the exhaust fan 10 .

[0065] The heavy water recovery and purification system for heavy water reactor units is used to purify heavy water recovered from heavy water reactor units, comprising the following steps:

[0066] 1. Start the exhaust fan 10 of the negative pressure exhaust filtration subsystem to establish a slight negative pressure of -20Pa to -30Pa for 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 of the heavy water reactor unit through the inlet quick connector 1;

[0068] 3. Heavy water recycled 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 recycles heavy water into the ultraviolet oxidation water tank 3. The circulation pump 13 is stopped to control the ultraviolet oxidation water tank 3 to stop water inflow after the ultraviolet oxidation water tank 3 reaches an appropriate liquid level. The liquid level of the ultraviolet oxidation water tank 3 should not exceed the nozzle of the dosing funnel 6 to avoid poor addition of hydrogen peroxide.

[0070] 5. Circulate the heavy water recovered from the heavy water reactor unit in the ultraviolet oxidation water tank 3, take samples through the liquid sampler 14, and measure 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 heavy water recovered by the heavy water reactor unit. Generally, the concentration of hydrogen peroxide is controlled to be 6 times the initial TOC concentration of heavy water recovered by the heavy water reactor unit.

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

[0073] 8. Regularly sample through the liquid sampler 14 to analyze the concentration of hydrogen peroxide in the heavy water recovered from the heavy water reactor unit in the ultraviolet oxidation water tank 3 until the concentration of hydrogen peroxide 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. Take samples through the liquid sampler 14 and measure various purification indicators of heavy water recovered from the heavy water reactor unit to confirm that the water quality is qualified;

[0076] 11 The qualified heavy water recovered from the heavy water reactor unit is transferred out of the heavy water reactor unit recovery heavy water purification system through the outlet quick connector 18 for storage;

[0077] 12. In the above steps, if the liquid leakage detector 15 gives an alarm, it is necessary to urgently stop the leak to prevent the leakage of heavy water recovered by the heavy water reactor unit from expanding.

[0078] In step 1, the molecular sieve adsorption bed 11 can adsorb 99.9% of the heavy water vapor in the exhaust gas of the air space of the ultraviolet oxidation water tank 3; the radioactive activity monitor 16 monitors the radioactive tritium activity of the gas at the outlet of the exhaust fan 10; when the radioactive tritium activity of the gas at the outlet of the exhaust fan 10 exceeds the warning value, the radioactive activity monitor 16 issues an alarm to remind the personnel to manually operate or automatically control the molecular sieve adsorption bed 11 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 is heated to a temperature of 100°C; ... Circulate, the air is heated by the electric heater to bring out the moisture inside the molecular sieve adsorption bed 11, and then the moisture is condensed by the condenser, and collected and refluxed to the ultraviolet oxidation water tank 3; the reflux valve 12 is arranged on the pipeline connecting the outlet of the exhaust fan 10 with the air space of the ultraviolet oxidation water tank 3, and the pressure of the air space of the ultraviolet oxidation water tank 3 is adjusted to -20Pa~-30Pa; the outlet of the exhaust fan 10 is connected to the air space pipeline of the ultraviolet oxidation water tank 3 to prevent the exhaust fan 10 from stalling due to running without medium; the pressure of the air space of the ultraviolet oxidation water tank 3 is monitored by the micropressure gauge 17.

[0079] In step 5, the concentration of hydrogen peroxide added should be adapted to the initial TOC level of heavy water recovered by the heavy water reactor unit: if the concentration of hydrogen peroxide added is too low, repeated addition is required, which prolongs the working time of the heavy water purification system for heavy water recovery by 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 the water with residual hydrogen peroxide enters the activated carbon bed and the resin bed, it will cause a certain degree of pulverization of the activated carbon and too fast saturation of the resin; according to experiments, the optimal concentration of hydrogen peroxide added is 6 times the initial TOC concentration of heavy water recovered by the heavy water reactor unit.

[0080] In step 7, UV oxidation generally uses a wavelength of 185nm and / or 254nm, wherein 185nm ultraviolet light is a shorter wavelength and higher energy, and its photon energy is equivalent to 6.7eV, while 254nm ultraviolet light has an energy equivalent to 4.88eV. In theory, the greater the power of ultraviolet light and the higher the concentration of hydrogen peroxide, the better the effect of degrading organic matter. In practical applications, during the operation of the ultraviolet lamp, light energy will be converted into heat energy, causing the temperature of the working medium to rise. Excessive medium temperature > 55°C will damage the resin and lose its exchange capacity, and the ions attached to the resin will be released, and even the resin will break, causing water quality to deteriorate; therefore, the power of the ultraviolet lamp should be limited according to the heat dissipation coefficient of the material during the operation of the system to ensure that the medium temperature does not exceed 55°C.

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

[0082] Table 1 Various indicators of heavy water recovered from heavy water reactor units after purification

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

[0084] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A heavy water recovery and purification system for a heavy water reactor unit, characterized in that: It includes an ultraviolet oxidation subsystem, a filtering and oil removal subsystem with a pressure-bearing and sealing structure, an adsorption exchange subsystem, a negative pressure exhaust filtration subsystem, a monitoring subsystem, a circulation pump (13), and a control subsystem; The filtering and oil removal subsystem is connected to the pipelines of the ultraviolet oxidation subsystem and the adsorption exchange subsystem respectively; the water inlet of the circulation pump (13) is connected to the pipelines of the filtering and oil removal subsystem and the ultraviolet oxidation subsystem respectively; the water outlet of the circulation 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 recovery purification system of the heavy water reactor unit; and the control subsystem controls the start and stop of the circulation pump (13), the ultraviolet oxidation subsystem and the negative pressure exhaust filtration subsystem.

2. The heavy water recovery and purification system for a heavy water reactor unit according to claim 1, characterized in that: The filtering and oil removal subsystem comprises a filter (2), a water inlet pipe and a water outlet pipe; the filter (2) comprises a pressure-bearing sealed shell and a filter element detachably fixed in the pressure-bearing sealed shell; the pressure-bearing sealed shell is provided with a water inlet (25) and a water outlet (26), the water inlet (25) is connected to the water inlet pipe, the water outlet (26) is connected to the water outlet pipe, and valves are provided on the water inlet pipe and the water 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 is composed of a stainless steel frame (27) wrapped from the inside to the outside, multiple layers of oil filter paper (28) and a stainless steel filter screen (29), and is threadedly connected to the bottom of the pressure-bearing sealing shell through a fixing screw (24) passing through the stainless steel frame (27), so that the filter element can be detachably fixed in the pressure-bearing sealing shell.

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 150 μm stainless steel filter screen; the multi-layer oil filter paper (28) is a wrinkled 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 comprises an ultraviolet oxidation water tank (3), an ultraviolet lamp tube (4), a quartz protective sleeve (5), a dosing funnel (6) and an inspection manhole flange cover (7); the top of the ultraviolet oxidation water tank (3) is threadedly sealed and connected to the inspection manhole flange cover (7); the inspection manhole flange cover (7) is provided with evenly distributed holes for placing the quartz protective sleeve (5), and the ultraviolet lamp tube (4) is placed in the quartz protective sleeve (5); the pipe mouth 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 inspection manhole flange cover (7) are connected. The dosing funnel (6) is connected to the pipeline of the ultraviolet oxidation water tank (3) 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 water inlet of the circulation pump (13) is respectively connected to the water outlet and the water outlet pipeline of the ultraviolet oxidation water tank (3), the water outlet of the circulation pump (13) is connected to the water inlet pipeline of the ultraviolet oxidation water tank (3), a valve is provided on the pipeline connecting the water inlet of the circulation pump (13) and the water outlet of the ultraviolet oxidation water tank (3), and a liquid sampler (14) and a valve are provided on the pipeline connecting the water outlet of the circulation pump (13) and the water 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 5, characterized in that: The adsorption exchange subsystem comprises an ion exchange resin bed (9) and an activated carbon bed (8); the water outlet of the circulation pump (13) is also connected to the water inlet pipeline of the activated carbon bed (8), the water outlet of the activated carbon bed (8) is connected to the water inlet pipeline of the ion exchange resin bed (9), the water outlet of the ion exchange resin bed (9) is connected to the water inlet pipeline of the ultraviolet oxidation water tank (3), the liquid sampler (14) is respectively connected to the pipeline connecting the water outlet of the ion exchange resin bed (9) and the water inlet of the ultraviolet oxidation water tank (3) and the pipeline connecting the water outlet of the circulation pump (13) and the water inlet of the ultraviolet oxidation water tank (3), and a three-way valve is provided on the pipelines connecting the water outlet of the circulation pump (13), the water inlet of the ultraviolet oxidation water tank (3) and the water inlet of the activated carbon bed (8).

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

8. The heavy water recovery and purification system for a heavy water reactor unit according to claim 6, characterized in that: The ion exchange resin bed (9) is filled with a core-grade uniform-particle gel-type mixed resin, which is composed of a core-grade uniform-particle gel-type H-type strongly acidic cation resin and an OH-type strongly basic anion resin in a 1:1 stoichiometric equivalent.

9. The heavy water recovery and purification system for a heavy water reactor unit according to claim 6, characterized in that: The negative pressure exhaust filtration subsystem comprises an exhaust fan (10) and a molecular sieve adsorption bed (11); the air space of the ultraviolet oxidation water tank (3) is connected to the molecular sieve adsorption bed (11) and the inlet pipeline of the exhaust fan (10) in sequence, the outlet of the exhaust fan (10) is connected to the air space pipeline of the ultraviolet oxidation water tank (3), and a reflux valve (12) is provided on the pipeline connecting the outlet of the exhaust fan (10) and the air space 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 monitoring subsystem comprises a liquid leakage detector (15), a radioactive activity monitor (16) and a micro pressure gauge (17); a stainless steel water receiving tray is arranged at the bottom of the heavy water recovery and purification system of the heavy water reactor unit, and the liquid leakage detector (15) is installed at the lowest point of the stainless steel water receiving tray through a base; the liquid leakage detector (15) comprises 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 water leakage at the lowest point of the stainless steel water receiving tray and the water level rises to the probe When the exhaust fan (10) is in the same position, the two electrodes are connected and an alarm is generated; a radioactivity monitor (16) is provided at the outlet of the exhaust fan (10); the radioactivity monitor (16) monitors the radioactive tritium activity of the gas at the outlet of the exhaust fan (10); when the radioactive tritium activity of the gas 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 micropressure gauge (17) provided on the top of the ultraviolet oxidation water tank (3) for monitoring the air space pressure of the ultraviolet oxidation water tank (3).

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

12. A heavy water reactor unit heavy water recovery and purification process, characterized in that: The steps include: 1) Starting the exhaust fan (10) of the negative pressure exhaust filtration subsystem to establish a slight negative pressure of -20Pa to -30Pa for the air space of the ultraviolet oxidation water tank (3); 2) starting the circulation pump (13) to pump the heavy water recovered from the heavy water reactor unit into the heavy water recovery purification system of the heavy water reactor unit through the inlet quick connector (1); 3) Heavy water recovered from 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 recycles heavy water into the ultraviolet oxidation water tank (3), and the circulation pump (13) is stopped to control the liquid level of the ultraviolet oxidation water tank (3) to stop the ultraviolet oxidation water tank (3) from entering the water level after the liquid level does not exceed the nozzle of the dosing funnel (6); 5) circulating the heavy water recovered from the heavy water reactor unit in the ultraviolet oxidation water tank (3), sampling through the liquid sampler (14), and measuring the initial TOC concentration of the heavy water recovered from the heavy water reactor unit; 6) According to the initial TOC concentration of heavy water recovered by the heavy water reactor unit, the amount of hydrogen peroxide to be added is determined to be 6 times the initial TOC concentration of heavy water recovered by the heavy water reactor unit; 7) Turn on the ultraviolet lamp (4), add a sufficient amount of hydrogen peroxide through the dosing funnel (6), and keep the ultraviolet oxidation water tank (3) in self-circulation; 8) regularly sampling through the liquid sampler (14) to analyze the concentration of hydrogen peroxide in the heavy water recovered from the heavy water reactor unit in the ultraviolet oxidation water tank (3) until the concentration of hydrogen peroxide 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) Sampling is performed by a liquid sampler (14) to measure various purification indicators of heavy water recovered from a heavy water reactor unit to confirm that the water quality is qualified; 11) The qualified heavy water recovered from the heavy water reactor unit is transferred out of the heavy water reactor unit recovery heavy water purification system through the outlet quick connector (18) for storage; 12) In the above steps, if the liquid leakage detector (15) sounds an alarm, it is necessary to urgently stop the leak to prevent the leakage of heavy water recovered by the heavy water reactor unit from expanding.

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

Images