Simulation device for determining zinc injection concentration during thermal state function test

Abstract

The utility model provides a simulation device for determining zinc injection concentration during a thermal state function test, and particularly relates to the technical field of nuclear power plants. The simulation device comprises a reaction kettle, a heater, a circulating pump, a water chemical control system and a zinc injection device, a sample is arranged in the reaction kettle, and the heater, the reaction kettle and the circulating pump form a circulating loop through connecting pipelines; a water outlet of the water chemical control system is communicated with a connecting pipeline between the circulating pump and the heater, and the water chemical control system is used for purifying inlet and outlet water of the reaction kettle; and the zinc injection device is communicated with the hydrochemical control system and injects zinc into the hydrochemical control system. According to the simulation device, zinc with different concentrations is injected into the reaction kettle through the hydrochemical control system, a sample is passivated under different zinc concentrations, and the film forming effect after passivation is observed, so that the optimal zinc injection concentration is obtained.

Description

Technical Field

[0001] This utility model relates to the field of nuclear power plant technology, specifically to a simulation device for determining the zinc injection concentration during a hot functional test. Background Technology

[0002] In the high-temperature, high-pressure water environment of pressurized water reactor (PWR) nuclear power plants, corrosion of primary loop equipment materials is a major threat to the safe operation of the plant and a primary cause of shutdowns. Zinc injection technology in the primary loop is a water chemistry control technique. By continuously injecting zinc solution into the primary loop, zinc ions effectively remove cobalt ions from the oxide film of equipment materials through a displacement reaction, promoting the formation of a denser and more stable nanoscale protective film structure. This microstructural evolution can significantly reduce the corrosion rate of primary loop system equipment (by 30-50%), suppress susceptibility to primary side stress corrosion cracking (PWSCC), and reduce the migration and deposition of corrosion products into the core region, resulting in a reduction of the radiation dose level outside the core by approximately 40%.

[0003] Statistics from the end of 2021 show that over 100 pressurized water reactor (PWR) units worldwide have implemented zinc injection technology. Among them, the US PWR units, fueled by FAMA, widely adopt this technology, with the longest recorded application period reaching 15 fuel cycles and the shortest reaching 3 fuel cycles. In the Westinghouse fuel supply system, 51% of the units have successfully implemented zinc injection technology. This indicates that zinc injection technology in the primary circuit has become a development trend in water chemistry technology for pressurized water reactor nuclear power units.

[0004] While the international nuclear energy field has reached a consensus on the benefits of zinc injection, a consensus on the optimal zinc concentration parameter remains elusive. Current engineering practices largely rely on empirical methods, lacking systematic research data supporting the understanding of film formation mechanisms on material surfaces. This is particularly true regarding the differentiated response characteristics of various materials in high-temperature, high-pressure (typical conditions: 290-330℃ / 15.5MPa) hydrochemical environments. This technological gap directly leads to a dual dilemma in zinc injection technology: excessive zinc injection may cause ZnO deposition and blockage, while insufficient injection fails to form an effective protective film. Therefore, there is an urgent need to develop a high-temperature, high-pressure simulation test platform to construct a precise primary loop operating environment and conduct systematic zinc concentration gradient experiments, providing theoretical basis and optimization solutions for engineering applications. Utility Model Content

[0005] In view of the problems existing in the prior art, the present invention provides a simulation device for determining the zinc concentration during hot functional testing, so as to solve the problem that the existing zinc injection technology cannot determine the zinc concentration.

[0006] To achieve the above and other related objectives, this utility model provides a simulation device for determining the zinc concentration during a hot functional test. The simulation device includes a reaction vessel, a heater, a circulating pump, a water chemistry control system, and a zinc injection device. A sample is placed inside the reaction vessel. The outlet of the heater is connected to the inlet of the reaction vessel via a connecting pipe. The outlet of the circulating pump is connected to the inlet of the heater via a connecting pipe, and the inlet of the circulating pump is connected to the outlet of the reaction vessel via a connecting pipe. The outlet of the water chemistry control system is connected to the connecting pipe between the circulating pump and the heater, and the water chemistry control system is used to purify the inlet and outlet water of the reaction vessel. The zinc injection device is connected to the water chemistry control system and injects zinc into the water chemistry control system.

[0007] In one embodiment of the present invention, the simulation device further includes a voltage regulator, which is disposed on the connecting pipe between the circulating pump and the heater.

[0008] In one embodiment of this utility model, the simulation device further includes a lower discharge pipe, an upper charge pipe, and a regeneration heat exchanger. One end of the lower discharge pipe is connected to the heater, and the other end is connected to the inlet of the water chemistry control system via the regeneration heat exchanger. One end of the upper charge pipe is connected to the outlet of the water chemistry control system, and the other end is connected to the connecting pipe between the circulating pump and the heater via the regeneration heat exchanger.

[0009] In one embodiment of this utility model, the simulation device further includes a cooling system, which includes a cooling tower, a cooler, and a cooling pipe. The cooler is disposed on the downflow pipe between the regenerated heat exchanger and the water chemistry control system, and the cooling tower forms a closed loop with the cooler through the cooling pipe.

[0010] In one embodiment of this utility model, the water chemistry control system includes a buffer tank, a dosing device, and a water quality analyzer. The dosing device is connected to the buffer tank and is used to add chemicals to the buffer tank. The buffer tank is equipped with an ion exchanger for purifying circulating water. The water quality analyzer is connected to the buffer tank and is used to detect the water quality parameters in the buffer tank.

[0011] In one embodiment of the present invention, the outlet of the heater is provided with a first pressure detection device and a first temperature detection device.

[0012] In one embodiment of this utility model, a flow meter is provided on the connecting pipe between the heater and the reactor, and a second temperature detection device and a second pressure detection device are provided at the water inlet of the reactor.

[0013] In one embodiment of this utility model, the reaction vessel is provided with multiple samples of different materials.

[0014] In one embodiment of this utility model, the connecting pipe is made of 316L stainless steel.

[0015] In one embodiment of this utility model, the design pressure of the reactor is not less than 20 MPa and the design temperature is not less than 350°C.

[0016] This invention provides a simulation device for determining the zinc injection concentration during hot functional testing. It simulates the primary loop water chemistry environment during hot functional testing using a high-temperature, high-pressure reactor. Samples of different materials are suspended inside the reactor, and different concentrations of zinc are added to the reactor using a water chemistry control system, allowing the samples to be continuously passivated under different zinc concentration conditions. After the passivation test, the film formation effect of different materials can be evaluated by surface elemental analysis, focused ion beam analysis, transmission electron microscopy (TEM) energy dispersive spectroscopy (EDS), and TEM high-resolution imaging, thereby determining the optimal zinc injection concentration for each material. This simulation device can be used to determine the primary loop zinc injection concentration during unit hot functional testing. Implementing primary loop zinc injection can reduce primary loop stress corrosion cracking and lower the radiation dose outside the reactor core. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other embodiments can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of one embodiment of a simulation device for determining the zinc concentration during the hot functional test of this utility model.

[0019] Component designation explanation:

[0020] 100. Reactor; 200. Circulation loop; 210. Heater; 220. Circulation pump; 230. Connecting pipe; 240. First temperature detection device; 250. First pressure detection device; 260. Second temperature detection device; 270. Second pressure detection device; 280. Flow meter; 300. Water chemistry control system; 310. Buffer tank; 311. Ion exchanger; 320. Water quality analyzer; 330. Zinc injection device; 340. Downflow pipe; 350. Upflow pipe; 360. Regenerator; 370. Pressure stabilizer; 380. Upflow pump; 400. Cooling system; 410. Cooler; 420. Cooling tower; 430. Cooling pipe. Detailed Implementation

[0021] The following specific examples illustrate the implementation of this utility model. Those skilled in the art can easily understand other advantages and effects of this utility model from the content disclosed in this specification. This utility model can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this utility model. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. It should also be understood that the terminology used in the embodiments of this utility model is for describing specific implementation schemes and not for limiting the scope of protection of this utility model. Test methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or according to the conditions recommended by the respective manufacturers.

[0022] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise specified in this invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention, as well as the prior art known to those skilled in the art and the description of this invention, may be implemented using any prior art methods, equipment, and materials similar to or equivalent to those in the embodiments of this invention.

[0023] It should be noted that the terms such as "upper", "lower", "left", "right", "middle" and "one" used in this specification are only for clarity of description and are not intended to limit the scope of implementation of this utility model. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered as within the scope of implementation of this utility model.

[0024] A pressurized water reactor nuclear power plant typically includes a primary loop, a secondary loop, and a tertiary loop, with the primary, secondary, and tertiary loops only transferring heat between each other.

[0025] For example, in a pressurized water reactor (PWR), the primary loop is the reactor coolant system, consisting of the reactor pressure vessel, main pumps, steam generators, and other components, located within the containment. The secondary loop consists of the steam generator, condensate pumps, steam-water separators, turbines, steam condensers (or condensers), and other components. The tertiary loop consists of auxiliary system equipment, including generators, water pumps, external evaporators, and other auxiliary equipment. The primary and secondary loops exchange heat through the steam generator, sequentially transferring the heat generated by nuclear fission to cool the various structures of the nuclear power plant. However, after years of operation, pressurized water reactor nuclear power plants inevitably experience corrosion of the loop materials, especially the primary loop. Zinc injection technology can protect the materials of the primary loop, mitigating intergranular corrosion and stress corrosion cracking of components. Although there are many cases of zinc injection in the primary loop both domestically and internationally, there is no consensus on the optimal zinc concentration during hot functional testing.

[0026] Based on this, the present invention provides a simulation device for determining the zinc concentration during hot functional testing. The device uses a high-temperature and high-pressure reactor to simulate the primary loop water chemical environment during hot functional testing, and sets samples of different materials in the reactor. Then, continuous passivation tests are carried out under different zinc concentration conditions. After the passivation test is completed, the film formation effect of the samples is analyzed to determine the optimal zinc concentration.

[0027] Please see Figure 1 The simulation device for determining the zinc concentration during the hot functional test of this invention includes: a reaction vessel 100, a heater 210, a circulating pump 220, a water chemistry control system 300, and a zinc injection device 330. The reaction vessel 100 contains a sample. The outlet of the heater 210 is connected to the inlet of the reaction vessel 100 via a connecting pipe 230. The outlet of the circulating pump 220 is connected to the inlet of the heater 210 via a connecting pipe 230, and the inlet of the circulating pump 220 is connected to the outlet of the reaction vessel 100 via a connecting pipe 230, thus forming a circulation loop 200 between the reaction vessel 100, the heater 210, and the circulating pump 220. The outlet of the water chemistry control system 300 is connected to the connecting pipe 230 between the circulating pump 220 and the heater 210, and the water chemistry control system 300 is used to purify the inlet and outlet water of the reaction vessel 100. The zinc injection device 330 is connected to the water chemistry control system 300 and injects zinc into the water chemistry control system 300.

[0028] In one embodiment, the reactor 100 is a 316 stainless steel high-temperature and high-pressure reactor used to simulate the water chemistry environment of the primary loop during hot functional testing. One or more samples of different materials can be placed inside the reactor 100. Preferably, multiple samples of different materials are placed inside the reactor 100 simultaneously to study the corrosion reactions of different materials in a single test, saving testing costs and improving sample efficiency. To ensure the comprehensiveness of sample corrosion, it is preferable to suspend the samples inside the reactor 100. For example, a hook can be installed at the top of the reactor 100, and the samples can be suspended from the hook by steel wire rope. The suspension height of the samples must ensure that the samples are completely immersed in the solution inside the reactor 100.

[0029] Furthermore, the reactor 100 is provided with an inlet and an outlet, the circulating pump 220 has an inlet and an outlet, and the heater 210 has an inlet and an outlet. The outlet of the circulating pump 220 is connected to the inlet of the heater 210 via a connecting pipe 230, and the outlet of the heater 210 is connected to the inlet of the reactor 100 via a connecting pipe 230, thereby forming a closed circulation loop 200. The water flowing out of the circulating pump 220 is heated by the heater 210 before entering the reactor 100, so that the water entering the reactor 100 reaches the actual operating temperature of the reactor. For example, the temperature of the coolant water before entering the reactor 100 after being heated by the heater 210 is controlled at 295℃±2℃. Furthermore, in order to better monitor temperature and pressure, the outlet of heater 210 is equipped with a first temperature detection device 240 and a first pressure detection device 250, and the inlet of reactor 100 is equipped with a second temperature detection device 260 and a second pressure detection device 270. The first temperature detection device 240 and the second temperature detection device 260 can be any device capable of detecting water temperature, such as a thermometer or thermocouple; the first pressure detection device 250 and the second pressure detection device 270 can be any device capable of detecting pressure, such as a pressure gauge.

[0030] In one embodiment, all connecting pipes 230 are made of 316L stainless steel, and the pipe type is not limited and can be selected according to actual conditions. As an example, connecting pipes 230 are selected as DN40 (nominal diameter 40 mm) PN8 (nominal pressure 8 bar), DN32 PN8, etc. A flow meter 280 is also provided on the connecting pipe 230 between the outlet of heater 210 and the inlet of reactor 100 to detect the flow rate of coolant water in the pipe. For example, the flow meter 280 is a balanced flow meter. Furthermore, the design pressure of the reactor 100, connecting pipes 230 and other equipment is not less than 20 MPa, and the design temperature is not less than 350°C. That is, the reactor 100, connecting pipes 230 and other equipment can withstand a maximum pressure of not less than 20 MPa and a maximum temperature of not less than 350°C, so that the simulation device of this embodiment can withstand the reaction pressure and reaction temperature of the actual reactor operation.

[0031] In one embodiment, the water chemistry control system 300 includes a buffer tank 310, a dosing device (not shown in the figure), and a water quality analyzer 320. The buffer tank 310 is equipped with an ion exchanger 311 for purifying the inlet and outlet water of the reactor 100. The ion exchange resin in the ion exchanger 311 can remove ionic impurities from the water. The dosing device is used to stably and continuously add reagents such as B, Li, and Zn to the buffer tank 310 to ensure that the water quality entering the reactor 100 meets the actual operating conditions of the reactor. The ion control accuracy of the dosing device for adding reagents such as B, Li, and Zn is not less than ±5% of the set value, and the concentration of a given solute in the circulation loop 200 can be maintained by the dosing device according to the flow rate of the circulation loop 200. The water quality analyzer 320 is used to monitor the water quality parameters in the buffer tank 310 in real time, including dissolved oxygen, pH value, pressure, inlet and outlet temperature, inlet and outlet conductivity, and flow rate.

[0032] The zinc injection device 330 is connected to the buffer tank 310 of the water chemistry control system 300 and is used to inject zinc into the buffer tank. The zinc injection device 330 can be any device capable of injecting zinc solution into the buffer tank 310. For example, the zinc injection device 330 includes a zinc injection tank body with an inlet and an outlet. The inlet is used to inject zinc-containing solution into the zinc injection tank body, and the outlet is connected to the buffer tank 310 through a zinc injection pipe. A dosing pump is provided on the zinc injection pipe, which can inject the zinc-containing solution in the zinc injection tank body into the buffer tank 310.

[0033] The coolant water in the circulation loop 200 may experience pressure fluctuations due to temperature changes (such as power fluctuations, equipment start-up and shutdown) during operation. Therefore, the simulation device also includes a pressure regulator 370 to maintain the high-pressure state of the circulation loop 200. In one embodiment, the pressure regulator 370 is installed on the connecting pipe 230 between the heater 210 and the circulation pump 220. The pressure regulator 370 is equipped with an electric heater and a spray system. The electric heater is located at the bottom of the pressure regulator 370 and is used to heat the water to generate steam and increase the pressure. The spray system is located at the top of the pressure regulator 370 and reduces the steam pressure by spraying low-temperature coolant into the steam space. By regulating the internal steam and water balance, the pressure is maintained within the set value range to avoid damage to the equipment and system caused by excessively high or low pressure.

[0034] Furthermore, to coordinate with the pressure stabilization process of the pressure regulator 370, the simulation device also includes a downflow pipe 340, an upflow pipe 350, and a regeneration heat exchanger 360. One end of the downflow pipe 340 is connected to the heater 210, and the other end is connected to the inlet of the buffer tank 310 of the water chemistry control system 300 via the regeneration heat exchanger 360. One end of the upflow pipe 350 is connected to the outlet of the buffer tank 310 of the water chemistry control system 300, and the other end is connected to the connecting pipe 230 between the circulating pump 220 and the heater 210 via the regeneration heat exchanger 360. An upflow pump 380, such as a high-pressure metering pump, is also installed on the upflow pipe 350 at the outlet of the buffer tank 310 to return the upflow to the heater 210. When the coolant water in the circulating loop 200 changes in volume due to temperature changes or leakage, the downflow flow rate is adjusted in conjunction with the upflow to maintain the water level of the pressure regulator 370 at the set value. Specifically, when the water volume in the circulation loop 200 increases, the expanded water is drawn from the heater 210 through the downflow pipe 340 (downflow) and enters the buffer tank 310 of the water chemical control system 300. The ion exchanger 311 in the buffer tank 310 removes impurities and radioactive substances from the water. When the water volume in the circulation loop 200 shrinks or leaks, the top-fill pump 380 returns the water from the buffer tank 310 to the heater 210 through the top-fill pipe 350 (top-fill). Both the downflow and top-fill flow pass through the regenerative heat exchanger 360 during their flow, achieving heat recovery. The downflow transfers heat to the regenerative heat exchanger 360, allowing the top-fill flow to absorb heat and increase its temperature as it passes through.

[0035] Because the simulation device generates a large amount of heat, a specific cooling device is required. In one embodiment, the simulation device further includes a cooling system 400, which includes a cooler 410, a cooling tower 420, and cooling pipes 430. The cooler 410 is installed on a drain pipe 340 between the regenerating heat exchanger 360 and the water chemistry control system 300. The cooling tower 420 and the cooler 410 form a closed loop through the cooling pipe 430. The drain stream maintains a high temperature after heat exchange in the regenerating heat exchanger 360. After flowing out of the regenerating heat exchanger 360, the drain stream enters the cooler 410, is cooled by the cooler 410, and then enters the cooling tower 420 for further cooling through the cooling pipe 430. After that, it flows back to the cooler 410, is cooled again, and then enters the buffer water tank 310 of the water chemistry control system 300.

[0036] The simulation device provided by this utility model can simulate the actual working conditions of a reactor during a hot functional test. By suspending samples of various materials in a high-temperature and high-pressure reactor 100 and adding zinc-containing solutions of different concentrations, the samples are continuously passivated for 300 hours under different zinc concentrations. By observing the film formation effect of samples of different materials after the passivation test, the optimal zinc concentration can be obtained.

[0037] The experimental procedure is illustrated below: Multiple samples of different materials can be suspended simultaneously in reactor 100. These samples are submerged in coolant water within reactor 100, and the entire circulation loop 200 is filled with coolant water. The coolant water in circulation loop 200 is heated by heater 210, and its temperature is controlled at 295±2℃ to simulate the actual operating conditions of a reactor. Then, zinc solution is injected into the buffer tank 310 of the water chemistry control system 300. During system heating, the pressure regulator 370 is kept in balance through the lower drain pipe 340 and the upper filling pipe 350. When the zinc concentration in the upper filling pipe 350 and the lower drain pipe 340 reaches the target concentration, it indicates that the concentration of the solution in reactor 100 has reached a stable target concentration (denoted as C1). At this point, the passivation film formation time begins. After the experimental time (300h) is reached, reactor 100 is closed, and the temperature is allowed to drop to room temperature and the pressure to atmospheric pressure. Afterward, reactor 100 is opened, and the samples are removed. During sampling, medical powder-free gloves were worn, and samples were collected sequentially and labeled. A second test was then conducted with a target zinc concentration of C2, following the same procedure. Passivation tests were then performed for C3, C4, and other different zinc concentrations. After the tests, surface elemental analysis, focused ion beam analysis, transmission electron microscopy (TEM) energy dispersive spectroscopy, and TEM high-resolution imaging analysis were performed on the samples at different zinc concentrations to evaluate the film-forming effect of different materials. The optimal zinc concentration was determined based on the film-forming effect.

[0038] This invention provides a simulation device for determining zinc concentration during hot functional testing. The device simulates the primary loop water chemistry environment during hot functional testing using a high-temperature, high-pressure reactor. Samples of different materials are suspended inside the reactor, and different concentrations of zinc are added using a water chemistry control system, allowing the samples to be continuously passivated under varying zinc concentrations. After the passivation test, the optimal zinc concentration for different materials is determined by analyzing the film formation effect on the samples. Therefore, this invention effectively overcomes some practical problems in existing technologies, thus possessing high utilization value and practical significance.

[0039] The above embodiments are merely illustrative of the principles and effects of this utility model and are not intended to limit the scope of this utility model. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this utility model. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this utility model should still be covered by the claims of this utility model.

Claims

1. A simulation device for determining the zinc injection concentration during hot functional testing, characterized in that The simulation device comprises: a reaction kettle with a sample inside; a heater, whose water outlet is connected to the water inlet of the reaction kettle through a connecting pipeline; a circulating pump, whose water outlet is connected to the water inlet of the heater through a connecting pipeline, and whose water inlet is connected to the water outlet of the reaction kettle through a connecting pipeline; a water chemical control system, whose water outlet is connected to the connecting pipeline between the circulating pump and the heater, and which is used to purify the water in and out of the reaction kettle; a zinc injection device, which is connected to the water chemical control system and injects zinc into the water chemical control system.

2. The simulation apparatus for determining the zinc injection concentration during hot functional test according to claim 1, wherein The simulation device further comprises a pressure stabilizer, which is arranged on the connecting pipeline between the circulating pump and the heater.

3. The simulation apparatus for determining the zinc injection concentration during hot functional test according to claim 2, wherein The simulation device further comprises a downflow pipeline, an upflow pipeline and a regenerative heat exchanger, one end of the downflow pipeline is connected to the heater, and the other end is connected to the water inlet of the water chemical control system through the regenerative heat exchanger; one end of the upflow pipeline is connected to the water outlet of the water chemical control system, and the other end is connected to the connecting pipeline between the circulating pump and the heater through the regenerative heat exchanger.

4. The simulation apparatus for determining the zinc injection concentration during hot functional test according to claim 3, wherein The simulation device further comprises a cooling system, which comprises a cooling tower, a cooler and a cooling pipeline, the cooler is arranged on the downflow pipeline between the regenerative heat exchanger and the water chemical control system, and the cooling tower forms a closed loop with the cooler through the cooling pipeline.

5. The simulation apparatus for determining the zinc injection concentration during hot functional test according to claim 1, wherein The water chemical control system comprises a buffer tank, a dosing device and a water quality detector, the dosing device is connected to the buffer tank and is used to add reagents into the buffer tank, the buffer tank is provided with an ion exchanger for purifying circulating water, and the water quality detector is connected to the buffer tank and is used to detect the water quality parameters in the buffer tank.

6. The simulation apparatus for determining the zinc injection concentration during hot functional test of claim 1, wherein The water outlet of the heater is provided with a first pressure detection device and a first temperature detection device.

7. The simulation apparatus for determining the zinc injection concentration during hot functional test according to claim 1, wherein The connecting pipeline between the heater and the reaction kettle is provided with a flow meter, and the water inlet of the reaction kettle is provided with a second temperature detection device and a second pressure detection device.

8. The simulation apparatus for determining the zinc injection concentration during hot functional test according to claim 1, wherein, The reaction kettle is provided with multiple samples made of different materials.

9. The simulation apparatus for determining the zinc injection concentration during hot functional test according to claim 1, wherein, The connecting pipeline is made of 316L stainless steel.

10. The simulation apparatus for determining the zinc injection concentration during hot functional test according to claim 1, wherein, The design pressure of the reaction kettle is not less than 20 MPa, and the design temperature is not less than 350℃.

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