Device and method for preparing high-concentration boric acid solution of safety injection system of nuclear power plant

Abstract

The invention belongs to the technical field of reactor operation, and provides a high-concentration boric acid solution preparation device and method for a safety injection system of a nuclear power plant, the device is provided with a boric acid solution preparation tank, a high-concentration boric acid solution fluctuation box, a high-concentration boric acid solution injection tank, a high-concentration boric acid solution circulating pump, a water injection valve, a boric acid solution transmission valve, a heater and a stirrer; according to the method, the temperature of a heat tracing wire and the temperature of a heater are adjusted, hot water is injected into a boric acid solution preparation tank, a high-concentration boric acid solution is conveyed to a high-concentration boric acid solution fluctuation box and a high-concentration boric acid solution injection tank, and sufficient circulating and uniform stirring are carried out; adding a small amount of calculated solid boric acid into the high-concentration boric acid solution fluctuation box by using a spoon, if the concentration of the boric acid solution is too high, injecting a proper amount of hot water into the high-concentration boric acid solution fluctuation box, and adjusting the concentration of the boric acid solution to 17000-19000 ppm. The working time is greatly shortened, and manpower is greatly reduced.

Description

Technical Field

[0001] The present application belongs to the field of reactor operation technology, and in particular relates to a device and method for preparing a high-concentration boric acid solution in a safety injection system of a nuclear power plant. Background Art

[0002] Boric acid is widely used in nuclear power plants to control reactor reactivity. A high-concentration boric acid solution with a boron concentration of 17,000 to 19,000 ppm is installed in the plant's safety injection system. Upon receiving a safety injection signal, the high-concentration boric acid solution is injected into the reactor core, providing negative reactivity. This injection of high-concentration boric acid ensures that the core remains in a safe subcritical state even in the event of a steam line rupture.

[0003] During each overhaul of a nuclear power plant, the high-concentration boric acid solution loop of the injection system needs to be emptied for inspection. Before the reactor is started, it is necessary to re-equip the reactor with a concentration of about 4m 3 A high concentration boric acid solution of 17000-19000ppm.

[0004] The current method for preparing a high-concentration boric acid solution for the injection system involves manually adding approximately 400 kg of solid boric acid, spoonful by spoonful, to the surge tank. To prevent boric acid crystallization, the process is slow, taking approximately 67 hours and requiring significant labor. Furthermore, the preparation of the high-concentration boric acid solution has a short overhaul window, potentially impacting the critical path and delaying the overhaul schedule.

[0005] Therefore, it is necessary to explore an optimized method for the preparation of high-concentration boric acid solution to solve the disadvantages of long working time and high manpower consumption in the preparation of high-concentration boric acid solution in the injection system. Summary of the Invention

[0006] The purpose of this application is to overcome the defects of the existing technology and provide a high-concentration boric acid solution preparation device and method for the nuclear power plant injection system, shorten the preparation time of the high-concentration boric acid solution, reduce the manpower required for the preparation of the high-concentration boric acid solution, and effectively prevent boric acid crystallization. It is suitable for all second-generation pressurized water reactor nuclear power plants.

[0007] In order to achieve the above objectives, this application provides the following technical solutions:

[0008] In a first aspect, the present application provides a high-concentration boric acid solution preparation device for a nuclear power plant injection system, wherein a boric acid solution preparation tank and a high-concentration boric acid solution surge tank are connected by a first pipeline, the high-concentration boric acid solution surge tank is connected to a high-concentration boric acid solution injection tank through a second pipeline, a high-concentration boric acid solution circulation pump is provided on the second pipeline, the high-concentration boric acid solution injection tank is connected to the high-concentration boric acid solution surge tank through a third pipeline, the water injection valve and the boric acid solution preparation tank are connected by a fourth pipeline, and a heater and an agitator are provided inside the boric acid solution preparation tank.

[0009] In some embodiments, a heating wire is wound around the first pipe.

[0010] In some embodiments, the automatic start temperature setting value of the heating wire is 68°C, and the automatic stop temperature setting value is 80°C.

[0011] In some embodiments, the fourth pipeline is provided with an instantaneous water heater.

[0012] In some embodiments, the instantaneous water heater is disposed upstream of the water filling valve.

[0013] In some embodiments, the instantaneous water heater heats the passing fresh water to 48°C.

[0014] In some embodiments, the heater is an electric heater.

[0015] In some embodiments, the automatic start temperature setting value of the electric heater is 68°C, and the automatic stop temperature setting value is 80°C.

[0016] In some embodiments, a boric acid solution transfer valve is provided on the first pipeline.

[0017] In a second aspect, the present application provides a method for preparing a high-concentration boric acid solution for a safety injection system of a nuclear power plant, based on the high-concentration boric acid solution preparation device for a safety injection system of a nuclear power plant, comprising:

[0018] Step 1: Confirm that the heating wire is adjusted to the automatic start temperature setting of 68℃ and the automatic stop temperature setting of 80℃; Confirm that the heater is adjusted to the automatic start temperature setting of 68℃ and the automatic stop temperature setting of 80℃;

[0019] Step 2: Put the instantaneous water heater into operation, open the water filling valve, and inject 48°C hot water into the boric acid solution preparation tank. After the required water level is reached, close the water filling valve;

[0020] Step 3: The heater automatically starts heating to 68℃~80℃;

[0021] Step 4: adding a fixed amount of solid boric acid into the boric acid solution preparation tank, starting the agitator, and completely dissolving the solid boric acid;

[0022] Step 5: Open the boric acid solution transfer valve to transfer the 18000 ppm high-concentration boric acid solution to the high-concentration boric acid solution surge tank and the high-concentration boric acid solution injection tank;

[0023] Step 6: Fully circulate and stir the high concentration boric acid solution surge tank and the high concentration boric acid solution injection tank through the high concentration boric acid solution circulation pump;

[0024] Step 7: Sampling the solution in the high-concentration boric acid solution surge tank to confirm that the boric acid solution concentration is within the range of 17,000 to 19,000 ppm;

[0025] Step 8: If the concentration of the boric acid solution is low, add a calculated small amount of solid boric acid to the high-concentration boric acid solution surge tank with a spoon; if the concentration of the boric acid solution is high, inject an appropriate amount of 68°C hot water into the high-concentration boric acid solution surge tank through the boric acid solution preparation tank; after fine-tuning, adjust the concentration of the boric acid solution in the high-concentration boric acid solution surge tank and the high-concentration boric acid solution injection tank to within the range of 17,000 to 19,000 ppm.

[0026] Compared with the prior art, the device and method for preparing a high-concentration boric acid solution for a nuclear power plant safety injection system provided in this application have the following beneficial effects:

[0027] This application significantly shortens the working time from the original 67 hours to 14 hours by improving the preparation method of the high-concentration boric acid solution in the injection system. It also significantly reduces manpower from the original 142 man-hours to 30 man-hours. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solution of this application, the following is a brief introduction to the drawings required for the technical description.

[0029] Figure 1 This is a schematic diagram of the structure of the high-concentration boric acid solution preparation device for the nuclear power plant safety injection system provided in this application;

[0030] Figure 2 This is an operational flow chart of the method for preparing a high-concentration boric acid solution for a nuclear power plant safety injection system provided in this application;

[0031] Figure 3 This is a schematic diagram comparing the effects before and after the optimization of the preparation of the high-concentration boric acid solution for the injection system provided in this application.

[0032] Description of reference numerals:

[0033] 1. Boric acid solution preparation tank; 2. High-concentration boric acid solution surge tank; 3. High-concentration boric acid solution injection tank; 4. High-concentration boric acid solution circulation pump; 5. Instantaneous water heater; 6. Water injection valve; 7. Boric acid solution transfer valve; 8. Heating wire; 9. Heater; 10. Agitator. DETAILED DESCRIPTION

[0034] The following is further explained in detail through specific implementation methods.

[0035] On the one hand, if Figure 1 As shown, the present application provides a high-concentration boric acid solution preparation device for a nuclear power plant safety injection system, comprising a boric acid solution preparation tank 1, a high-concentration boric acid solution surge tank 2, a high-concentration boric acid solution injection tank 3, a high-concentration boric acid solution circulation pump 4, a water injection valve 6, a boric acid solution transfer valve 7, a heater 9, and an agitator 10. The device utilizes the boric acid solution preparation tank 1 to prepare a high-concentration boric acid solution with a concentration of 18,000 ppm for the safety injection system.

[0036] The boric acid solution preparation tank 1 and the high-concentration boric acid solution surge tank 2 are connected by a first pipeline. The outlet of the high-concentration boric acid solution surge tank 2 is connected to a second pipeline, which leads to the high-concentration boric acid solution injection tank 3. A high-concentration boric acid solution circulation pump 4 is provided on the second pipeline. The outlet of the high-concentration boric acid solution injection tank 3 is connected to a third pipeline, which leads to the high-concentration boric acid solution surge tank 2. The flow direction between the high-concentration boric acid solution surge tank 2 and the high-concentration boric acid solution injection tank 3 is as follows: the solution flows out from the outlet of the high-concentration boric acid solution surge tank 2, flows into the inlet of the high-concentration boric acid solution injection tank 3 through the second pipeline and enters therein, then flows out from the outlet of the high-concentration boric acid solution injection tank 3, flows into the inlet of the high-concentration boric acid solution surge tank 2 through the third pipeline and enters therein.

[0037] The water injection valve 6 is connected to the boric acid solution preparation tank 1 via a fourth pipeline. A heater 9 and a stirrer 10 are provided in the boric acid solution preparation tank 1.

[0038] Boric acid solution preparation tank 1 is used to prepare 7,000 ppm or 11,000 ppm boric acid solution for other systems. A boric acid solution transfer valve 7 is provided on the first pipeline between the boric acid solution preparation tank 1 and the high-concentration boric acid solution surge tank 2. Although the boric acid solution preparation tank 1 has the process flow conditions for transferring boric acid to the high-concentration boric acid solution surge tank 2, it does not have the technical conditions for preparing a high-concentration boric acid solution with a concentration of 18,000 ppm. In addition, the crystallization temperature of a high-concentration boric acid solution of 18,000 ppm is 53°C. The heater 9 in the boric acid solution preparation tank 1 was originally designed with a startup temperature set at 48°C and a shutdown temperature set at 53°C. This can maintain the temperature of the clean water in the boric acid solution preparation tank 1 within the range of 48°C to 53°C, but does not have the technical conditions for preparing a high-concentration boric acid solution of 18,000 ppm.

[0039] To this end, this device uses a higher-power electric heater for heater 9, and changes the automatic start-up temperature setting from 48°C to 68°C, and the automatic shutdown temperature setting from 53°C to 80°C. After this modification, the temperature of the clean water in boric acid solution preparation tank 1 can be maintained in the range of 68°C to 80°C, which is higher than the crystallization temperature of 53°C for a high-concentration boric acid solution of 18,000 ppm. Boric acid solution preparation tank 1 can prepare a high-concentration boric acid solution of 18,000 ppm.

[0040] Furthermore, the biggest risk point in the transmission of high-concentration boric acid solution is boric acid crystallization. This device has a heating wire 8 wrapped around the first pipeline between the boric acid solution preparation tank 1 and the high-concentration boric acid solution surge tank 2. In the original design, the automatic start-up temperature of the heating wire 8 was set at 55°C, and the automatic shutdown temperature was set at 60°C. The crystallization temperature of an 18,000 ppm high-concentration boric acid solution is 53°C. During the transmission of high-concentration boric acid solution, due to the long transmission pipeline, there is a problem of natural heat dissipation. The 2°C margin is not enough to ensure that boric acid crystallization does not occur during the transmission of high-concentration boric acid solution. This device further modifies the automatic start-up temperature of the heating wire 8 from 55°C to 68°C, and the automatic shutdown temperature from 60°C to 80°C. The 10°C margin can ensure that boric acid crystallization does not occur during the transmission of high-concentration boric acid solution.

[0041] In one embodiment, the clean water injected into the boric acid solution preparation tank 1 is demineralized water at room temperature. The clean water in the boric acid solution preparation tank 1 must be heated to 68°C by a heater 9 before solid boric acid can be added to the boric acid solution preparation tank 1. This heating process takes about 3 hours, and especially up to 4 hours in winter. To this end, the device adds a quick water heater 5 to the water injection pipe, and the water injection valve 6 is set between the boric acid solution preparation tank 1 and the quick water heater 5. The temperature of the clean water passing through the quick water heater 5 can reach 48°C. After the modification, the heating time of the clean water in the boric acid solution preparation tank 1 can be shortened to about 1 hour.

[0042] On the other hand, based on the above-mentioned high-concentration boric acid solution preparation device for the nuclear power plant injection system, the present application also provides a method for preparing a high-concentration boric acid solution for the nuclear power plant injection system, wherein the boric acid solution preparation tank 1 prepares and transmits 18000ppm of boric acid solution to the high-concentration boric acid solution surge tank 2 and the high-concentration boric acid solution injection tank 3. Figure 2 The specific steps are as follows:

[0043] Step 1: Confirm that the heating wire 8 is adjusted to the automatic start temperature setting of 68°C and the automatic stop temperature setting of 80°C; confirm that the heater 9 is adjusted to the automatic start temperature setting of 68°C and the automatic stop temperature setting of 80°C;

[0044] Step 2: Put the instantaneous water heater 5 into operation, open the water injection valve 6, and inject 48°C hot water into the boric acid solution preparation tank 1. After the required water level is reached, close the water injection valve 6;

[0045] Step 3: Heater 9 automatically starts heating to 68℃~80℃;

[0046] Step 4: Add a certain amount of solid boric acid into the boric acid solution preparation tank 1, start the stirrer 10, and completely dissolve the solid boric acid;

[0047] Step 5: Open the boric acid solution transfer valve 7 to transfer the 18000 ppm high concentration boric acid solution to the high concentration boric acid solution surge tank 2 and the high concentration boric acid solution injection tank 3;

[0048] Step 6: The high concentration boric acid solution surge tank 2 and the high concentration boric acid solution injection tank 3 are fully circulated and stirred by the high concentration boric acid solution circulation pump 4;

[0049] Step 7: Sampling the solution in the high-concentration boric acid solution surge tank 2 to confirm that the boric acid solution concentration is within the range of 17,000 to 19,000 ppm;

[0050] Step 8: If the boric acid solution concentration is low, use a spoon to add a small amount of solid boric acid to the high-concentration boric acid solution surge tank 2. If the boric acid solution concentration is high, inject an appropriate amount of 68°C hot water into the high-concentration boric acid solution surge tank 2 through the boric acid solution preparation tank 1. After fine-tuning, adjust the boric acid solution concentration in the high-concentration boric acid solution surge tank 2 and the high-concentration boric acid solution injection tank 3 to within the range of 17,000 to 19,000 ppm.

[0051] For example, a high-concentration boric acid solution was prepared for the injection system of a unit in a nuclear power plant. During the 309 overhaul, a detailed implementation plan for the preparation of high-concentration boric acid solution for the injection system was developed according to this method to address the issues of time-consuming preparation of high-concentration boric acid solution for the injection system, delaying the key overhaul path, and occupying a large amount of manpower. The final sampling result of the high-concentration boric acid solution for the injection system was 17406 ppm, which was quite consistent with the expected calculation. At the same time, the working time was greatly shortened from 67 hours in the original plan to 14 hours; the manpower was greatly reduced from 142 man-hours in the original plan to 30 man-hours. Ultimately, the goal of quickly and accurately preparing high-concentration boric acid solution was achieved, solving the long-standing problem of time-consuming and manpower-intensive preparation of high-concentration boric acid solution for the injection system in nuclear power plants. It can be seen that the implementation of the technical solution of this application greatly shortened the working time and significantly reduced the manpower occupation, as shown in the following table.

[0052]

[0053] Therefore, the present application can significantly shorten the time for preparing a high-concentration boric acid solution and reduce the manpower required for preparing a high-concentration boric acid solution, and can effectively prevent boron crystallization.

[0054] The above description is only a specific implementation method of the present application, but the scope of protection of the present application is not limited thereto. Any changes or replacements that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed in this application should be covered by the scope of protection of the present application.

Claims

1. A device for preparing high-concentration boric acid solution for a safety injection system of a nuclear power plant, characterized in that: A boric acid solution preparation tank (1) and a high-concentration boric acid solution surge tank (2) are connected via a first pipeline; the high-concentration boric acid solution surge tank (2) is connected to a high-concentration boric acid solution injection tank (3) via a second pipeline; a high-concentration boric acid solution circulation pump (4) is provided on the second pipeline; the high-concentration boric acid solution injection tank (3) is connected to the high-concentration boric acid solution surge tank (2) via a third pipeline; a water injection valve (6) and the boric acid solution preparation tank (1) are connected via a fourth pipeline; and a heater (9) and a stirrer (10) are provided inside the boric acid solution preparation tank (1).

2. The high-concentration boric acid solution preparation device for the safety injection system of a nuclear power plant according to claim 1, characterized in that: A heating wire (8) is wound around the first pipeline.

3. The high-concentration boric acid solution preparation device for the safety injection system of a nuclear power plant according to claim 2, characterized in that: The automatic start temperature setting value of the heating wire (8) is 68°C, and the automatic stop temperature setting value is 80°C.

4. The high-concentration boric acid solution preparation device for the safety injection system of a nuclear power plant according to claim 1, characterized in that: The fourth pipeline is provided with an instantaneous water heater (5).

5. The high-concentration boric acid solution preparation device for the safety injection system of a nuclear power plant according to claim 4, characterized in that: The instantaneous water heater (5) is arranged upstream of the water injection valve (6).

6. The high-concentration boric acid solution preparation device for the safety injection system of a nuclear power plant according to claim 5, characterized in that: The instantaneous water heater (5) heats the passing clean water to 48°C.

7. The high-concentration boric acid solution preparation device for the safety injection system of a nuclear power plant according to claim 1, characterized in that: The heater (9) is an electric heater.

8. The high-concentration boric acid solution preparation device for the safety injection system of a nuclear power plant according to claim 7, characterized in that: The automatic start temperature setting value of the electric heater is 68°C, and the automatic stop temperature setting value is 80°C.

9. The high-concentration boric acid solution preparation device for the safety injection system of a nuclear power plant according to claim 1, characterized in that: A boric acid solution transfer valve (7) is provided on the first pipeline.

10. A method for preparing a high-concentration boric acid solution for a safety injection system of a nuclear power plant, based on the device for preparing a high-concentration boric acid solution for a safety injection system of a nuclear power plant according to any one of claims 1 to 9, characterized in that: include: Step 1: Confirm that the heating wire (8) is adjusted to the automatic start temperature setting value and the automatic stop temperature setting value; confirm that the heater (9) is adjusted to the automatic start temperature setting value and the automatic stop temperature setting value; Step 2: Put the instantaneous water heater (5) into operation, open the water injection valve (6), add hot water to the boric acid solution preparation tank (1), and close the water injection valve (6) after the required water level is reached; Step 3: The heater (9) is automatically put into operation to heat to 68°C to 80°C; Step 4: adding a fixed amount of solid boric acid into the boric acid solution preparation tank (1), and starting the stirrer (10) to completely dissolve the solid boric acid; Step 5: Open the boric acid solution transfer valve (7) to transfer the high-concentration boric acid solution to the high-concentration boric acid solution surge tank (2) and the high-concentration boric acid solution injection tank (3); Step 6: Circulating and stirring the high-concentration boric acid solution surge tank (2) and the high-concentration boric acid solution injection tank (3) through the high-concentration boric acid solution circulation pump (4); Step 7: sampling the solution in the high-concentration boric acid solution surge tank (2) to confirm that the concentration of the boric acid solution is within the range of 17,000 to 19,000 ppm; Step 8: If the concentration of the boric acid solution is low, add the calculated amount of solid boric acid with a spoon at the high concentration boric acid solution surge tank (2); If the concentration of the boron solution is too high, hot water is injected into the high-concentration boric acid solution surge tank (2) through the boric acid solution preparation tank (1); The concentration of the boric acid solution in the high-concentration boric acid solution surge tank (2) and the high-concentration boric acid solution injection tank (3) is adjusted to a range of 17,000 to 19,000 ppm.

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