Experimental loop and method for simulating migration and deposition of pressurized water reactor corrosion products

Abstract

The invention belongs to the technical field of nuclear power, and particularly relates to an experimental loop and method for simulating migration and deposition of pressurized water reactor corrosion products. Comprising a main pipeline loop, an auxiliary bypass, a chemical volume bypass and a monitoring bypass are connected to the main pipeline loop, the main loop is used for simulating the thermal hydraulic environment of a pressurized water reactor primary loop and simulating circulation loops under different working conditions, and a coolant solution circularly flows in the loop to drive corrosion products to migrate. The device has the beneficial effects that (1) the thermal hydraulic environment of a primary loop of a nuclear power plant can be simulated, migration and deposition of corrosion products on the surface of a primary loop pipeline are simulated, and research on deposition behaviors of the corrosion products in the primary loop is facilitated; (2) an alkaline reagent is added into the auxiliary branch to adjust the pH value of the solution, so that the influence of pH on a corrosion product source item in the loop can be researched.

Description

Technical Field

[0001] The invention belongs to the technical field of nuclear power, and in particular relates to an experimental circuit and method for simulating the migration and deposition of corrosion products in a pressurized water reactor. Background Art

[0002] With the increase in power and the requirement for long fuel cycles of pressurized water reactor nuclear power plants, the impact of corrosion products in the primary circuit has been increasingly valued. Although the primary coolant system (RCS) and steam generator pipes have good corrosion resistance, due to the large contact area between the pipes and the coolant, a large amount of corrosion products will enter the coolant and be re-introduced into the RCS pipes and steam generators after the core is activated, thus affecting the dose of operation and maintenance personnel.

[0003] According to literature reports, about 4% of corrosion products come from RCS, and about 96% of corrosion products come from steam generators (especially high-nickel alloys). According to foreign nuclear power plant experience, more than 90% of occupational exposure comes from external exposure caused by activated corrosion product sources on the surface of equipment during overhaul. In order to reduce the collective dose, it is necessary to study how to minimize corrosion products, and then study the migration and deposition behavior of corrosion products in the primary circuit.

[0004] In summary, studying the migration and deposition behavior of corrosion products in the primary circuit of a pressurized water reactor has important practical significance for reducing radioactive sources. In order to study the generation, transport, deposition, and morphological transformation of corrosion products under different operating conditions of a pressurized water reactor, it is necessary to design a thermal hydraulic experimental circuit that simulates the migration and deposition of corrosion products in a pressurized water reactor.

[0005] For example, the patent document CN118362365A discloses a simulation experimental circuit of corrosion products on the surface of the fuel cladding, which simulates the formation of corrosion products on the surface of the fuel cladding. The experimental system includes a main circuit and an auxiliary branch. This experimental circuit simulates the behavior of corrosion products on a loop pipeline, and can functionally simulate the migration and deposition of corrosion products under different working conditions. The experimental system includes a main circuit, an auxiliary bypass, a chemical volume bypass and a monitoring bypass. Summary of the invention

[0006] The purpose of the present invention is to provide an experimental loop for simulating the migration and deposition of corrosion products in a pressurized water reactor, which can realize the research on the source term of corrosion products in the primary loop of a pressurized water reactor.

[0007] The technical solution of the present invention is as follows: an experimental loop for simulating the migration and deposition of corrosion products in a pressurized water reactor, comprising a main pipeline loop, to which an auxiliary bypass, a chemical volume bypass and a monitoring bypass are respectively connected, the main loop is used to simulate the thermal hydraulic environment of a primary loop of a pressurized water reactor, and to simulate a circulation loop under different working conditions, wherein a coolant solution circulates in the loop to drive the migration of corrosion products.

[0008] The main pipeline loop is connected with a circulation pump, a pressure stabilizer, a first flow meter, a first experimental section, a heater, a second experimental section, a heat exchanger, and a fifth experimental section in sequence. The water tank is connected to the main loop pipeline of the circulation pump inlet section. A safety valve and a stop valve are arranged in the main loop.

[0009] An auxiliary bypass is arranged in the main pipeline loop for injecting medicine and gas into the solution in the loop. The auxiliary bypass is connected between the circulation pump and the pipeline at the water tank outlet.

[0010] The auxiliary bypass is connected in series with a stop valve, a cooler, a stirring bottle, a peristaltic pump, a flow meter, a second online pH meter and a second dissolved hydrogen and dissolved oxygen detector. A branch for drug injection and gas injection is arranged in front of the inlet of the stirring bottle, which are connected to the drug adding device and the gas cylinder respectively.

[0011] A chemical volume bypass is arranged in the main pipeline loop, one end of the chemical volume bypass is connected to the main loop pipeline between the heat exchanger inlet and the second experimental section, and the other end is connected to the main loop pipeline between the heat exchanger outlet and the fifth experimental section. The chemical volume bypass can purify and circulate the solution in the circulation loop.

[0012] The chemical volume bypass is connected in series with a stop valve, a peristaltic pump, a third experimental section, a filter and a fourth experimental section.

[0013] A monitoring bypass is arranged in the main pipeline loop, one end of the monitoring bypass is connected to the main loop pipeline between the safety valve and the stop valve, and the other end is connected to the main loop pipeline between the first flow meter and the first experimental section.

[0014] The monitoring bypass is serially connected with a stop valve, a second flow meter, an online pH value measuring instrument and a dissolved hydrogen and dissolved oxygen detector.

[0015] A branch is arranged between the inlet and outlet of the circulation pump of the main pipeline loop, and a regulating valve is connected in series in the branch to adjust the flow rate of the circulation pump.

[0016] An experimental method for simulating the migration and deposition of corrosion products in a pressurized water reactor comprises the following steps:

[0017] S1: Open the experimental loop, turn on the circulation pump, and adjust the flow rate and flow velocity of the main loop;

[0018] S2: Open the gas cylinder valve of the auxiliary bypass and introduce hydrogen into the loop to remove oxygen;

[0019] S3: Turn on the heater and heat exchanger, adjust the opening of each valve, and raise the solution temperature to a predetermined temperature;

[0020] S4: Add the specified granular corrosion products and alkaline reagents through the dosing device of the auxiliary bypass, stir them thoroughly in the stirring bottle and then pass them into the main circuit;

[0021] S5: Change the flow rate and flow velocity of the experimental section, or adjust the power of the heater to change the temperature of the experimental section, or add different alkaline reagents to adjust the pH value of the solution, or replace the pipes with different shapes as the experimental section to study the influence of different factors on the corrosion products of the experimental section;

[0022] S6: After the solution flow in the experimental section stabilizes, observe and study the migration and deposition of corrosion products in the experimental section, and measure the thickness and weight of the corrosion product deposition in the experimental section.

[0023] The beneficial effects of the present invention are: (1) It can simulate the thermal hydraulic environment of the primary circuit of a nuclear power plant, simulate the migration and deposition of corrosion products on the surface of the primary circuit pipeline, and contribute to the study of the deposition behavior of corrosion products in the primary circuit. (2) By adding an alkaline reagent to the auxiliary branch to adjust the pH value of the solution, the influence of pH on the source term of corrosion products in the circuit can be studied. (3) By adjusting the opening of each valve and changing the flow rate of the experimental circuit, the influence of the flow rate on the source term of corrosion products in the circuit can be studied. (4) By adjusting the power of the heater and changing the temperature at the experimental section, the influence of the coolant temperature on the source term of corrosion products in the circuit can be studied. By setting pipes of different shapes as experimental sections, the influence of the pipe shape on the source term of corrosion products in the circuit can be studied. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic diagram of the overall structure of an experimental circuit for simulating the migration and deposition of corrosion products in a pressurized water reactor provided by the present invention;

[0025] Figure 2 This is a schematic diagram of the straight tube experimental section;

[0026] Figure 3 It is a schematic diagram of the U-bend experimental section;

[0027] Figure 4 Schematic diagram of the L-shaped bend experimental section.

[0028] In the figure: 1 water tank, 2 circulation pump, 3 voltage regulator, 4 heater, 5 heat exchanger, 6 chiller, 7-1 first peristaltic pump, 7-2 second peristaltic pump, 8 filter, 9-1 first flow meter, 9-2 second flow meter, 9-3 third flow meter, 9-4 fourth flow meter, 10-1 first experimental section, 10-2 second experimental section, 10-3 third experimental section, 10-4 fourth experimental section, 10-5 fifth experimental section, 11-1 first online pH meter, 11-2 second online pH meter, 12-1 first dissolved hydrogen detector instrument, 12-2 second dissolved hydrogen detector, 13-1 first dissolved oxygen detector, 13-2 second dissolved oxygen detector, 14 cooler, 15 gas cylinder, 16 dosing device, 17 stirring bottle, 18 stop valve, 18-1 first stop valve, 18-2 second stop valve, 18-3 third stop valve, 18-4 fourth stop valve, 18-5 fifth stop valve, 18-6 sixth stop valve, 18-7 seventh stop valve, 18-8 eighth stop valve, 18-9 ninth stop valve, 18-10 tenth stop valve, 19 safety valve. DETAILED DESCRIPTION

[0029] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] In view of the increase in the collective dose of nuclear power plants caused by corrosion products in the primary circuit of a pressurized water reactor, the present invention proposes an experimental circuit and method for simulating the migration and deposition of corrosion products in a pressurized water reactor to study the behavior of the corrosion products.

[0031] like Figure 1 As shown in the figure, an experimental loop for simulating the migration and deposition of corrosion products in a pressurized water reactor has four loops, including a main pipeline loop, an auxiliary bypass, a chemical volume bypass and a monitoring bypass. The main pipeline loop is connected to the auxiliary bypass, the chemical volume bypass and the monitoring bypass respectively. The main loop is used to simulate the thermal hydraulic environment of the primary loop of the pressurized water reactor and simulate the circulation loop under different working conditions. The coolant solution circulates in the loop to drive the migration of corrosion products.

[0032] The main pipeline loop includes a water tank 1, a circulating pump 2, a pressure regulator 3, a first flow meter 9-1, a first experimental section 10-1, a heater 4, a second experimental section 10-2, a heat exchanger 5, and a fifth experimental section 10-5. The experimental section is used to observe the migration and deposition of corrosion products, and the solution circulates in the main loop. The heat exchanger 5 is connected to an external chiller 6 to simulate the steam generator of the first loop of a pressurized water reactor and cool the entire loop.

[0033] Specifically, the water tank 1 is connected to the circulation pump 2 through a pipeline, a stop valve 18 is provided on the pipeline, the circulation pump 2 is connected to the first flow meter 9-1 through a pipeline, a third stop valve 18-3, a safety valve 19 and a fourth stop valve 18-4 are sequentially provided on the pipeline, a regulator 3 is connected to the pipeline between the third stop valve 18-3 and the safety valve 19, the first flow meter 9-1 is connected to the first experimental section 10-1 through a pipeline, the first experimental section 10-1 is connected to the heater 4 through a pipeline, and the heater 4 is connected to the first experimental section 10-1 through a pipeline. The second experimental section 10-2 is connected to the heat exchanger 5 through a pipeline, and a sixth stop valve 18-6 is arranged on the pipeline between the second experimental section 10-2 and the heat exchanger 5. The heat exchanger 5 is externally connected to a chiller 6, and a first stop valve 18-1 is arranged on a connecting pipe between the heat exchanger and the chiller 6. The heat exchanger 5 is connected to the fifth experimental section 10-5 through a pipeline, and an eighth stop valve 18-8 is arranged on the pipeline. The fifth experimental section 10-5 is connected to the pipeline between the stop valve 8 and the circulation pump 2.

[0034] A branch is arranged between the inlet and outlet of the main loop circulation pump 2, and a second stop valve 8-2 is connected in series in the branch to adjust the flow rate of the circulation pump.

[0035] Among them, the circulation pump 2 is used to simulate the flow of the solution in the entire experimental loop, the voltage stabilizer 3 is used to stabilize the loop pressure, the heater 4 heats the solution in the loop to reach the predetermined temperature of the experiment, the heat exchanger 5 is externally connected to the chiller 6 to cool the solution in the circulating loop, and the experimental section is made of transparent material to facilitate the observation and photography of the movement of corrosion product particles in the experimental section.

[0036] The auxiliary bypass includes a return water heat exchanger 14, a stirring bottle 17, a second peristaltic pump 7-2, a third flowmeter 9-3, a second online pH value measuring instrument 11-2, a second dissolved hydrogen detector 12-2 and a second dissolved oxygen detector 13-2. A dosing point and a hydrogen injection point are provided on the pipeline between the outlet of the return water heat exchanger 14 and the inlet of the stirring bottle 17, which are respectively connected to the dosing device 16 and the gas cylinder 15. The tenth stop valve 18-10 and the fourth flowmeter 9-4 are arranged between the gas cylinder 15 and the auxiliary bypass pipeline for flow monitoring and controlling the flow rate of hydrogen injection. It can be understood that the auxiliary bypass is used to add the required substances to the circulation loop. After the solution of the drug and gas injected in the bypass is fully stirred in the stirring bottle, it is re-injected into the main loop.

[0037] Specifically, the auxiliary bypass is used to inject medicine and gas into the solution in the loop, the auxiliary bypass is connected between the pipeline of the circulation pump 2 and the outlet of the water tank 1, the ninth stop valve 18-9 is connected to the pipeline close to the circulation pump 2, the ninth stop valve 18-9 is connected to the return water heat exchanger 14, the return water heat exchanger 14 is connected to the stirring bottle 17 through a pipeline, the dosing device 16 is connected to the pipeline between the return water heat exchanger 14 and the stirring bottle 17, the fourth flow meter 9-4 is connected to the pipeline between the return water heat exchanger 14 and the dosing device 16, the fourth flow meter 9-4 is connected to the gas cylinder 15 through a pipeline, and the fourth flow meter 9-4 is connected to the gas cylinder 15 through a pipeline. -4 and the gas cylinder 15 are provided with a tenth stop valve 18-10, which is connected to the second peristaltic pump 7-2 through a pipeline, the second peristaltic pump 7-2 is connected to the third flow meter 9-3 through a pipeline, the third flow meter 9-3 is connected to the second online pH value meter 11-2 through a pipeline, the second online pH value meter 11-2 is connected to the second dissolved hydrogen detector 12-2 and the second dissolved oxygen detector 13-2 in parallel through a pipeline, and the second dissolved hydrogen detector 12-2 and the second dissolved oxygen detector 13-2 are connected to the position between the water tank 1 and the circulation pump 2 close to the water tank through a pipeline.

[0038] The chemical volume bypass includes the seventh stop valve 18-7, the first peristaltic pump 7-1, the third experimental section 10-3, the filter 8 and the fourth experimental section 10-4. One end of the chemical volume bypass is connected to the main loop pipeline between the heat exchanger inlet and the second experimental section, and the other end is connected to the main loop pipeline between the heat exchanger outlet and the fifth experimental section. The chemical volume bypass can purify the solution in the circulation loop.

[0039] Specifically, the inlet of the chemical volume bypass is arranged on the pipeline between the second experimental section 10-2 and the sixth stop valve 18-6 through the seventh stop valve 18-7, and the outlet is arranged on the pipeline between the eighth stop valve 18-8 and the heat exchanger 5 through the fourth experimental section 10-4. The seventh stop valve 18-7 is connected to the first peristaltic pump 7-1, the third experimental section 10-3, the filter 8 and the fourth experimental section 10-4 in sequence through the pipeline. It can be seen that the chemical volume bypass purifies the inlet and outlet water of the circulation loop.

[0040] The monitoring bypass includes a fifth stop valve 18-5, a second flow meter 9-2, a first online pH value measuring instrument 11-1, a first dissolved hydrogen detector 12-1 and a first dissolved oxygen detector 13-1, which are used to monitor the pH value, dissolved hydrogen and dissolved oxygen values ​​of the main pipeline loop solution.

[0041] Specifically, the fifth stop valve 18-5 of the monitoring bypass is connected to the pipeline between the safety valve 19 and the fourth stop valve 18-4, and the fifth stop valve 18-5 is connected to the second flow meter 9-2 and the first online pH value meter 11-1 in turn through the pipeline. The first online pH value meter 11-1 is connected to the first dissolved hydrogen detector 12-1 and the first dissolved oxygen detector 13-1 in parallel. The first dissolved hydrogen detector 12-1 and the first dissolved oxygen detector 13-1 are connected to the pipeline between the first flow meter 9-1 and the first experimental section 10-1.

[0042] In addition, the inlet and outlet ends of the heater 4 are provided with pressure measuring points and temperature measuring points, the inlet and outlet ends of the heat exchanger 5 are provided with temperature measuring points, and the outlet sections of the circulation pump 2 and the first peristaltic pump 7-1 and the second peristaltic pump 7-2 are provided with pressure measuring points.

[0043] Among them, the main loop pipelines at both ends of the heater 4 are connected in series with the temperature and pressure measurement points. The main loop pipelines on both sides of all experimental sections are connected in series with the temperature and pressure measurement points. The outlets of the circulation pump 2 and the peristaltic pump are connected in series with the pressure measurement points. The main loop pipeline of the experimental loop is made of 0Cr18Ni10Ti. The experimental section pipeline can be detachably connected, such as Figure 2-4 As shown, the experimental section pipeline includes different shapes, and different pipeline shapes can be selected each time to carry out the experiment. The pipeline diameters of different experimental pipelines are the same. An iron sheet sample is arranged on the inner wall of the pipeline of the experimental section to measure the weight of corrosion product deposition.

[0044] An experimental method for simulating the migration and deposition of corrosion products in a pressurized water reactor comprises the following steps:

[0045] S1: Put the primary solution simulation liquid into the water tank and the loop, turn on the experimental loop and the circulation pump, and adjust the flow rate and flow velocity of the main loop;

[0046] S2: Open the gas cylinder valve of the auxiliary bypass to inject hydrogen into the loop to remove oxygen;

[0047] S3: Turn on the heater and heat exchanger, adjust the opening of each valve, and raise the solution temperature to a predetermined temperature;

[0048] S4: loading simulated corrosion product particles and alkaline reagent into a dosing device, mixing and stirring them, and then introducing them into the main circuit;

[0049] S5: Observe the fluid and corrosion product deposition and migration in the experimental section. During the experiment, the valve opening can be changed to change the flow rate, the heater power can be controlled to change the temperature of different experimental sections, alkaline reagents can be added to change the pH value of the loop solution, and the experimental section pipeline can be replaced to change the pipeline shape to study the influence of various factors on the behavior of corrosion products in the experimental section.

[0050] S6: After the experimental loop has been running stably for 2 hours, record the temperature and pressure values ​​measured at each measuring point in the experimental section, use an oxide thickness gauge to measure the thickness of the deposition layer in the experimental section, and after the experiment, recover the iron sheet samples in the experimental section pipeline and measure the weight difference before and after to estimate the weight of the corrosion product deposition.

[0051] Specifically, this PWR primary loop experimental loop can be used to study:

[0052] 1. Migration and deposition of corrosion products at different flow rates;

[0053] 2. Migration and deposition of corrosion products at different temperatures;

[0054] 3. Migration and deposition of corrosion products at different solution pH values;

[0055] 4. Migration and deposition of corrosion products under different pipeline shapes;

[0056] More specifically, the solution in the primary loop uses boric acid and lithium hydroxide as solvents, wherein the initial concentration of boron is 1000 mg / kg and the initial concentration of lithium is 2.2 mg / kg.

[0057] When the heater is used to heat the circuit, the temperature of the experimental section is made to reach the temperature designed for the experimental requirements, and the temperature range is between 310℃±15℃.

[0058] When adding drugs in the auxiliary bypass, ensure that the solution and the medium are fully mixed and reacted in the stirring bottle. The flow rate of the solution in the bypass is controlled at 3m / s~5m / s to ensure uniform mixing and sufficient reaction.

[0059] The above description is a further explanation of the present invention in combination with the implementation mode, and does not limit the patent scope of the present invention. Various changes, modifications and improvements made by technicians in this field using the contents of the specification and drawings should all be included in the patent scope of the present invention.

Claims

1. An experimental circuit for simulating the migration and deposition of corrosion products in a pressurized water reactor, characterized in that: It includes a main pipeline loop, to which an auxiliary bypass, a chemical volume bypass and a monitoring bypass are connected respectively. The main loop is used to simulate the thermal hydraulic environment of a pressurized water reactor primary loop and to simulate a circulating loop under different working conditions. The coolant solution circulates in the loop to drive the migration of corrosion products.

2. An experimental circuit for simulating the migration and deposition of corrosion products in a pressurized water reactor as claimed in claim 1, characterized in that: The main pipeline loop is connected with a circulation pump, a pressure stabilizer, a first flow meter, a first experimental section, a heater, a second experimental section, a heat exchanger, and a fifth experimental section in sequence. The water tank is connected to the main loop pipeline of the circulation pump inlet section. A safety valve and a stop valve are arranged in the main loop.

3. An experimental circuit for simulating the migration and deposition of corrosion products in a pressurized water reactor as claimed in claim 1, characterized in that: An auxiliary bypass is arranged in the main pipeline loop for injecting medicine and gas into the solution in the loop. The auxiliary bypass is connected between the circulation pump and the pipeline at the water tank outlet.

4. An experimental circuit for simulating the migration and deposition of corrosion products in a pressurized water reactor as claimed in claim 3, characterized in that: The auxiliary bypass is connected in series with a stop valve, a cooler, a stirring bottle, a peristaltic pump, a flow meter, a second online pH meter and a second dissolved hydrogen and dissolved oxygen detector. Branches for drug injection and gas injection are arranged in front of the stirring bottle inlet, and are connected to the drug adding device and the gas cylinder respectively.

5. The experimental circuit for simulating the migration and deposition of corrosion products in a pressurized water reactor according to claim 1, characterized in that: A chemical volume bypass is arranged in the main pipeline loop, one end of the chemical volume bypass is connected to the main loop pipeline between the heat exchanger inlet and the second experimental section, and the other end is connected to the main loop pipeline between the heat exchanger outlet and the fifth experimental section. The chemical volume bypass can purify and circulate the solution in the circulation loop.

6. An experimental circuit for simulating the migration and deposition of corrosion products in a pressurized water reactor as claimed in claim 5, characterized in that: The chemical volume bypass is connected in series with a stop valve, a peristaltic pump, a third experimental section, a filter and a fourth experimental section.

7. An experimental circuit for simulating the migration and deposition of corrosion products in a pressurized water reactor as claimed in claim 1, characterized in that: A monitoring bypass is arranged in the main pipeline loop, one end of the monitoring bypass is connected to the main loop pipeline between the safety valve and the stop valve, and the other end is connected to the main loop pipeline between the first flow meter and the first experimental section.

8. An experimental circuit for simulating the migration and deposition of corrosion products in a pressurized water reactor as claimed in claim 1, characterized in that: The monitoring bypass is serially connected with a stop valve, a second flow meter, an online pH value measuring instrument and a dissolved hydrogen and dissolved oxygen detector.

9. An experimental circuit for simulating the migration and deposition of corrosion products in a pressurized water reactor as claimed in claim 1, characterized in that: A branch is arranged between the inlet and outlet of the circulation pump of the main pipeline loop, and a regulating valve is connected in series in the branch to adjust the flow rate of the circulation pump.

10. A method for applying the circuit according to any one of claims 1 to 9, characterized in that: The steps include: S1: Open the experimental loop, turn on the circulation pump, and adjust the flow rate and flow velocity of the main loop; S2: Open the gas cylinder valve of the auxiliary bypass and introduce hydrogen into the loop to remove oxygen; S3: Turn on the heater and heat exchanger, adjust the opening of each valve, and raise the solution temperature to a predetermined temperature; S4: Add the specified granular corrosion products and alkaline reagents through the dosing device of the auxiliary bypass, stir them thoroughly in the stirring bottle and then pass them into the main circuit; S5: Change the flow rate and flow velocity of the experimental section, or adjust the power of the heater to change the temperature of the experimental section, or add different alkaline reagents to adjust the pH value of the solution, or replace the pipes with different shapes as the experimental section to study the influence of different factors on the corrosion products of the experimental section; S6: After the solution flow in the experimental section stabilizes, observe and study the migration and deposition of corrosion products in the experimental section, and measure the thickness and weight of the corrosion product deposition in the experimental section.

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