Method for measuring leakage rate of heat exchanger of containment spray system of nuclear power plant

Abstract

The application relates to a method for measuring the leakage rate of a heat exchanger of a containment spray system of a nuclear power plant, which comprises the following steps: before the leakage rate test of the heat exchanger of the containment spray system of the nuclear power plant, sampling a refueling water tank of the containment spray system of the nuclear power plant to obtain a refueling water tank sample, and sampling a device cooling water system of the containment spray system of the nuclear power plant to obtain a first device cooling water system sample; after the leakage rate test of the heat exchanger of the containment spray system of the nuclear power plant, sampling the device cooling water system of the containment spray system of the nuclear power plant to obtain a second device cooling water system sample; measuring the tritium activity of the refueling water tank sample, the first device cooling water system sample and the second device cooling water system sample; and calculating the leakage rate of the heat exchanger of the containment spray system of the nuclear power plant. The method for measuring the leakage rate of the heat exchanger of the containment spray system of the nuclear power plant is fast and accurate, and can realize the leakage rate measurement of the heat exchanger of the containment spray system of the nuclear power plant by using the daily analysis means of the nuclear power plant.

Description

Technical Field

[0001] This invention relates to the field of chemical analysis technology for nuclear power plants, and in particular to a method for measuring the leakage rate of a heat exchanger in a containment spray system of a nuclear power plant. Background Technology

[0002] The containment spray system is a crucial cooling pathway for the containment vessel in the event of an accident in the primary loop of a nuclear power plant. As the boundary of the radioactive medium, the heat exchanger of the containment spray system is a critical component, making leak rate measurement an important task. Current methods for leak rate measurement suffer from drawbacks such as demanding instrument requirements and cumbersome testing procedures. Summary of the Invention

[0003] Therefore, it is necessary to address the problems of high instrument requirements and cumbersome testing processes in measuring the leakage rate of heat exchangers in the containment spray system of nuclear power plants. This method provides a method for measuring the leakage rate of heat exchangers in the containment spray system of nuclear power plants. This method uses routine analytical methods in nuclear power plants to quickly and accurately measure the leakage rate of heat exchangers in the containment spray system of nuclear power plants, ensuring that the sealing performance of heat exchangers in the containment spray system of nuclear power plants meets the operating requirements of nuclear power plants.

[0004] To address the above problems, this invention provides a method for measuring the leakage rate of a heat exchanger in a containment spray system of a nuclear power plant, comprising the following steps:

[0005] Step 1: Before the start of the leakage rate test of the heat exchanger of the containment spray system of the nuclear power plant, take samples of the refueling water tank of the containment spray system of the nuclear power plant to obtain the refueling water tank sample, and take samples of the cooling water system of the equipment of the containment spray system of the nuclear power plant to obtain the first equipment cooling water system sample.

[0006] Step 2: Conduct a leak rate test on the heat exchanger of the containment spray system in the nuclear power plant;

[0007] Step 3: After the leakage rate test of the heat exchanger of the containment spray system of the nuclear power plant is completed, samples are taken from the cooling water system of the containment spray system of the nuclear power plant to obtain the second equipment cooling water system sample;

[0008] Step 4: Measure the tritium activity of the refueling water tank sample, the first equipment cooling water system sample, and the second equipment cooling water system sample;

[0009] Step 5: Calculate the leakage rate of the heat exchanger in the nuclear power plant containment spray system based on the tritium activity of the refueling tank sample, the first equipment cooling water system sample, and the second equipment cooling water system sample, the test duration of the leakage rate test of the heat exchanger in the containment spray system, and the water volume of the cooling water system of the nuclear power plant containment spray system.

[0010] Working Principle: During the leak rate test of the heat exchanger in the containment spray system of a nuclear power plant, water is drawn from the refueling water tank, cooled by the equipment cooling water on the heat exchanger shell side, and then returned to the refueling water tank. The water in the refueling water tank contains a certain amount of radioactive tritium, while the equipment cooling water on the heat exchanger shell side does not contain radioactive tritium during normal operation. If a leak occurs in the heat exchanger, the tritium activity in the equipment cooling water on the heat exchanger shell side will change significantly. By measuring the tritium activity in the refueling water tank and the equipment cooling water, the leak rate of the heat exchanger in the nuclear power plant containment spray system is calculated based on the tritium activity of the refueling water tank and the equipment cooling water.

[0011] Furthermore, the nuclear power plant containment spray system includes a heat exchanger, a refueling water tank, and an equipment cooling water system. The inlet and outlet of the heat exchanger tube side are respectively connected to the refueling water tank via pipelines. A pump is installed on the pipeline connecting the heat exchanger tube side inlet to the refueling water tank. An equipment cooling water outlet valve is installed at the heat exchanger shell side outlet. The heat exchanger shell side inlet pipeline is connected to the equipment cooling water system, and the heat exchanger shell side outlet is connected to the equipment cooling water system via the equipment cooling water outlet valve. Water from the refueling water tank enters the heat exchanger tube side via the heat exchanger tube side inlet as the heat exchanger tube side water source. Equipment cooling water from the equipment cooling water system enters the heat exchanger shell side via the heat exchanger shell side inlet as the heat exchanger shell side water source. The heat exchanger tube side water source is cooled by the heat exchanger shell side water source and then returns to the refueling water tank. Opening the equipment cooling water outlet valve allows the heat exchanger shell side water source to return to the equipment cooling water system, thus achieving heat exchanger shell side water source circulation.

[0012] Furthermore, in step 2, before conducting the leakage rate test of the heat exchanger in the containment spray system of the nuclear power plant, the cooling water outlet valve of the equipment is closed to avoid the impact of the cooling water flow on the shell side of the heat exchanger on the leakage rate test of the heat exchanger in the containment spray system of the nuclear power plant.

[0013] Further, in step 3, after the leakage rate test of the heat exchanger of the containment spray system of the nuclear power plant is completed, the equipment cooling water outlet valve is opened, and after the equipment cooling water on the heat exchanger shell side is circulated and mixed, a sample of the equipment cooling water system is taken to obtain a second equipment cooling water system sample.

[0014] Further, in step 4, the tritium activity of the feed tank sample, the first equipment cooling water system sample, and the second equipment cooling water system sample is measured using a liquid scintillation counter.

[0015] Further, in step 5, the leakage rate of the heat exchanger in the containment spray system of the nuclear power plant is calculated according to the following formula:

[0016]

[0017] In the formula: Leakage rate of heat exchangers in containment spray system of nuclear power plant, in L / h; The volume of the equipment's cooling water system is expressed in liters (L). The tritium activity of the sample from the cooling water system of the second equipment is expressed in MBq / t. The tritium activity of the sample from the cooling water system of the first equipment is expressed in MBq / t. The value represents the tritium activity of the refueling tank sample, expressed in MBq / t; T represents the duration of the leak rate test of the heat exchanger in the containment spray system of the nuclear power plant, expressed in hours.

[0018] Furthermore, when the tritium activity of both the first equipment cooling water system sample and the second equipment cooling water system sample is below the detection limit of the liquid scintillation counter, ( The leakage rate of the heat exchanger in the containment spray system of a nuclear power plant is calculated by replacing the lower limit value of the liquid flash counter with the lowest detectable leakage rate of the liquid flash counter.

[0019] Beneficial technical effects of the present invention:

[0020] The present invention provides a method for measuring the leakage rate of the heat exchanger in the containment spray system of a nuclear power plant. Using a liquid flash counter, which is routinely used in nuclear power plants, as the detection means, the method quickly and accurately obtains the tritium activity of samples from the refueling tank, the equipment cooling water system before the test, and the equipment cooling water system after the test. The method then calculates the leakage rate of the heat exchanger in the containment spray system of the nuclear power plant, ensuring that the sealing performance of the heat exchanger in the containment spray system of the nuclear power plant meets the operating requirements of the nuclear power plant. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the containment spray system in a nuclear power plant.

[0022] In the diagram, 1 is the feed tank; 2 is the pump; 3 is the equipment cooling water; 4 is the heat exchanger; and 5 is the equipment cooling water outlet valve. Detailed Implementation

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein in the specification is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “equivalent to”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0024] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0025] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments.

[0026] This embodiment provides a method for measuring the leakage rate of a heat exchanger in a containment spray system of a nuclear power plant, including the following steps:

[0027] Step 1: Before the start of the leakage rate test of the heat exchanger of the containment spray system of the nuclear power plant, take samples of the refueling water tank of the containment spray system of the nuclear power plant to obtain the refueling water tank sample, and take samples of the cooling water system of the equipment of the containment spray system of the nuclear power plant to obtain the first equipment cooling water system sample.

[0028] Step 2: Conduct a leak rate test on the heat exchanger of the containment spray system in the nuclear power plant;

[0029] Step 3: After the leakage rate test of the heat exchanger of the containment spray system of the nuclear power plant is completed, samples are taken from the cooling water system of the containment spray system of the nuclear power plant to obtain the second equipment cooling water system sample;

[0030] Step 4: Measure the tritium activity of the refueling water tank sample, the first equipment cooling water system sample, and the second equipment cooling water system sample;

[0031] Step 5: Calculate the leakage rate of the heat exchanger in the nuclear power plant containment spray system based on the tritium activity of the refueling tank sample, the first equipment cooling water system sample, and the second equipment cooling water system sample, the test duration of the leakage rate test of the heat exchanger in the containment spray system, and the water volume of the cooling water system of the nuclear power plant containment spray system.

[0032] Working Principle: During the leak rate test of the heat exchanger in the containment spray system of a nuclear power plant, water is drawn from the refueling water tank, cooled by the equipment cooling water on the heat exchanger shell side, and then returned to the refueling water tank. The water in the refueling water tank contains a certain amount of radioactive tritium, while the equipment cooling water on the heat exchanger shell side does not contain radioactive tritium during normal operation. If a leak occurs in the heat exchanger, the tritium activity in the equipment cooling water on the heat exchanger shell side will change significantly. By measuring the tritium activity in the refueling water tank and the equipment cooling water, the leak rate of the heat exchanger in the nuclear power plant containment spray system is calculated based on the tritium activity of the refueling water tank and the equipment cooling water.

[0033] See Figure 1In this embodiment, the nuclear power plant containment spray system includes a heat exchanger 4, a refueling water tank 1, and an equipment cooling water system; the inlet and outlet of the heat exchanger 4 are respectively connected to the refueling water tank 1 by pipes; a pump 2 is installed on the pipe connecting the inlet of the heat exchanger 4 to the refueling water tank 1; an equipment cooling water outlet valve 5 is installed at the outlet of the heat exchanger 4 on the shell side; the inlet pipe of the heat exchanger 4 on the shell side is connected to the equipment cooling water system; and the outlet of the heat exchanger 4 on the shell side is connected to the equipment cooling water system through the equipment cooling water outlet valve 5. Water in the refill water tank 1 enters the heat exchanger 4 via the tube-side inlet, serving as the tube-side water source. Equipment cooling water 3 in the equipment cooling water system enters the heat exchanger 4 via the shell-side inlet, serving as the shell-side water source. After being cooled by the shell-side water source, the tube-side water returns to the refill water tank 1. Opening the equipment cooling water outlet valve 5 allows the shell-side water source to return to the equipment cooling water system, thus achieving shell-side water circulation.

[0034] In this embodiment, before conducting the leakage rate test of the heat exchanger in the containment spray system of the nuclear power plant in step 2, the cooling water outlet valve 5 of the equipment is closed to avoid the impact of the cooling water flow on the shell side of the heat exchanger 4 on the leakage rate test of the heat exchanger in the containment spray system of the nuclear power plant.

[0035] In this embodiment, in step 3, after the leakage rate test of the heat exchanger of the containment spray system of the nuclear power plant is completed, the equipment cooling water outlet valve 5 is opened, and after the equipment cooling water on the shell side of the heat exchanger 4 is circulated and mixed, a sample of the equipment cooling water system is taken to obtain a second equipment cooling water system sample.

[0036] In this embodiment, step 4 involves measuring the tritium activity of the feed tank sample, the first equipment cooling water system sample, and the second equipment cooling water system sample using a liquid scintillation counter.

[0037] In this embodiment, step 5 involves calculating the leakage rate of the heat exchanger in the containment spray system of a nuclear power plant according to the following formula:

[0038]

[0039] In the formula: Leakage rate of heat exchangers in containment spray system of nuclear power plant, in L / h; The volume of the equipment's cooling water system is expressed in liters (L). The tritium activity of the sample from the cooling water system of the second equipment is expressed in MBq / t. The tritium activity of the sample from the cooling water system of the first equipment is expressed in MBq / t. The value represents the tritium activity of the refueling tank sample, expressed in MBq / t; T represents the duration of the leak rate test of the heat exchanger in the containment spray system of the nuclear power plant, expressed in hours.

[0040] In this embodiment, when the tritium activity of both the first equipment cooling water system sample and the second equipment cooling water system sample is lower than the detection limit of the liquid scintillation counter, ( The leakage rate of the heat exchanger in the containment spray system of a nuclear power plant is calculated by replacing the lower limit value of the liquid flash counter with the lowest detectable leakage rate of the liquid flash counter.

[0041] In this embodiment, the tritium activity of the refueling tank sample is 832 MBq / t; the tritium activities of both the first and second equipment cooling water system samples are below the detection limit of the liquid scintillation counter, and the measured tritium activities of both samples are below the detection limit of the liquid scintillation counter; the detection limit of the liquid scintillation counter is 0.04 MBq / t; the test duration for the leakage rate of the heat exchanger in the containment spray system of the nuclear power plant is 2 hours; the water volume of the equipment cooling water system is 60,000 L; the calculated leakage rate of the heat exchanger in the containment spray system of the nuclear power plant is 0.144 L / h, which is the lowest detectable leakage rate of the liquid scintillation counter.

[0042] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for measuring the leakage rate of a heat exchanger in a containment spray system of a nuclear power plant, characterized in that, Includes the following steps: Step 1: Before the start of the leakage rate test of the heat exchanger of the containment spray system of the nuclear power plant, take samples of the refueling water tank of the containment spray system of the nuclear power plant to obtain the refueling water tank sample, and take samples of the cooling water system of the equipment of the containment spray system of the nuclear power plant to obtain the first equipment cooling water system sample. Step 2: Conduct a leak rate test on the heat exchanger of the containment spray system in the nuclear power plant; Step 3: After the leakage rate test of the heat exchanger of the containment spray system of the nuclear power plant is completed, samples are taken from the cooling water system of the containment spray system of the nuclear power plant to obtain the second equipment cooling water system sample; Step 4: Measure the tritium activity of the refueling water tank sample, the first equipment cooling water system sample, and the second equipment cooling water system sample; Step 5: Calculate the leakage rate of the heat exchanger in the nuclear power plant containment spray system based on the tritium activity of the refueling tank sample, the first equipment cooling water system sample, and the second equipment cooling water system sample, the test duration of the leakage rate test of the heat exchanger in the containment spray system, and the water volume of the cooling water system of the equipment in the nuclear power plant containment spray system. The containment spray system of the nuclear power plant includes a heat exchanger (4), a refueling water tank (1), and an equipment cooling water system; the inlet and outlet of the heat exchanger (4) are respectively connected to the refueling water tank (1) by pipes; a pump (2) is installed on the pipe connecting the inlet of the heat exchanger (4) to the refueling water tank (1); an equipment cooling water outlet valve (5) is installed at the outlet of the heat exchanger (4) on the shell side; the inlet pipe of the heat exchanger (4) on the shell side is connected to the equipment cooling water system; and the outlet of the heat exchanger (4) on the shell side is connected to the equipment cooling water system through the equipment cooling water outlet valve (5). Step 5: Calculate the leakage rate of the heat exchanger in the containment spray system of the nuclear power plant according to the following formula: ； In the formula: Leakage rate of heat exchangers in containment spray system of nuclear power plant, in L / h; The volume of the equipment's cooling water system is expressed in liters (L). The tritium activity of the sample from the cooling water system of the second equipment is expressed in MBq / t. The tritium activity of the sample from the cooling water system of the first equipment is expressed in MBq / t. The value represents the tritium activity of the refueling tank sample, expressed in MBq / t; T represents the duration of the leak rate test of the heat exchanger in the containment spray system of the nuclear power plant, expressed in hours.

2. The method for measuring the leakage rate of the heat exchanger in the containment spray system of a nuclear power plant according to claim 1, characterized in that, Step 2: Before conducting the leakage rate test of the heat exchanger of the containment spray system in a nuclear power plant, close the cooling water outlet valve of the equipment (5).

3. The method for measuring the leakage rate of a heat exchanger in a nuclear power plant containment spray system according to claim 1, characterized in that, Step 3: After the leakage rate test of the heat exchanger of the containment spray system of the nuclear power plant is completed, open the equipment cooling water outlet valve (5), and after the equipment cooling water on the shell side of the heat exchanger (4) is circulated and mixed, take a sample of the equipment cooling water system to obtain a second equipment cooling water system sample.

4. The method for measuring the leakage rate of the heat exchanger in the containment spray system of a nuclear power plant according to claim 1, characterized in that, Step 4: Measure the tritium activity of the feed tank sample, the first equipment cooling water system sample, and the second equipment cooling water system sample using a liquid scintillation counter.

5. The method for measuring the leakage rate of a heat exchanger in a nuclear power plant containment spray system according to claim 4, characterized in that, When the tritium activity of both the first and second equipment cooling water system samples is below the detection limit of the liquid scintillation counter, ( The leakage rate of the heat exchanger in the containment spray system of a nuclear power plant is calculated by replacing the lower limit value of the liquid flash counter with the lowest detectable leakage rate of the liquid flash counter.

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