Method for controlling turbidity of reactor pool before loading and unloading during overhaul of nuclear power plant

Abstract

The invention belongs to the technical field of reactor pool water turbidity control before nuclear power plant refueling overhaul loading / unloading, and particularly relates to a reactor pool turbidity control method before nuclear power plant overhaul loading / unloading. Front-end control is carried out on work related to reactor pool water quality from a unit refueling overhaul preparation stage, a descending stage, a low-low water level stage and an ascending stage; in the preparation stage, a water filling source refueling water tank before reactor pool unloading is purified before unit refueling overhaul, it is expected that purification is conducted till the turbidity of the refueling water tank is smaller than 0.1 NTU, and it is guaranteed that the water filling source of the reactor pool is clear before unloading; in the descending stage, the unit overhaul first loop 80 DEG C platform purification is completed, and discharging is completed; in the low-water-level stage, a primary loop coolant is discharged to a refueling water tank after unloading is completed, and a primary loop system is filled with water after low-water-level maintenance is completed; and the ascending stage is from primary loop water filling to charging completion. Therefore, the purpose of controlling the influence of turbid water in the reactor pool before loading / unloading on normal loading / unloading work is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of turbidity control of reactor water pool before overhaul loading / unloading of nuclear power plant, and particularly relates to a method for controlling turbidity of reactor water pool before overhaul loading / unloading of nuclear power plant. Background Art

[0002] Before loading / unloading during refueling overhaul of nuclear power plants, the reactor pool must be filled with boron-containing water to act as a biological shield for surrounding workers. However, after the reactor pool is filled with water, the water may be turbid, which may make it difficult for loading / unloading personnel to see the relevant parts inside the pressure vessel at the bottom of the reactor pool, resulting in the inability to perform loading / unloading work normally; at this time, it is necessary to wait for the reactor pool purification unit to purify the water in the pool before loading / unloading work can be performed, which delays the key path of the overhaul main line, affects the overall construction period of the refueling overhaul, and causes great economic losses.

[0003] This problem is common in many nuclear power plants in China. For example, one nuclear power plant had its critical overhaul path delayed by about 16 hours because the reactor pool was filled with boron-containing water and the water became turbid. Summary of the invention

[0004] The purpose of the present invention is to provide a method for controlling the turbidity of a reactor water pool before overhaul loading and unloading of a nuclear power plant, which can comprehensively control the work related to the water quality of the reactor water pool from the preparation stage, the down stage, the low water level stage, and the up stage of the nuclear power unit refueling overhaul, so as to achieve the purpose of controlling the turbidity of the reactor water pool before loading / unloading to prevent the loading / unloading work from being carried out normally.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for controlling the turbidity of a reactor pool before overhaul loading and unloading of a nuclear power plant, which performs front-end control of work related to the water quality of the reactor pool from the unit refueling overhaul preparation stage, the down stage, the low-low water level stage, and the up stage;

[0007] The preparation stage is to purify the refueling water tank of the reactor pool before unloading before the unit refueling overhaul, and it is expected that the turbidity of the refueling water tank will be less than 0.1NTU to ensure that the water source for filling the reactor pool is clear before unloading;

[0008] The down stage is from the purification of the 80°C platform of the primary circuit of the unit overhaul to the completion of unloading, including the centralized peeling and purification of the corrosion products of the 80°C platform of the primary circuit, the inspection of the reactor pool before filling the reactor pool with water, the purification of the water quality of the reactor pool after filling the reactor pool with water, and whether the turbidity of the water quality of the reactor pool meets the unloading condition judgment criteria;

[0009] The low-low water level stage is from the time when the unloading is completed and the primary circuit coolant is discharged to the refueling water tank to the time when the low-low water level maintenance is completed and before the primary circuit system is filled with water, including the refueling water tank purification and the reactor water pool inspection before the primary circuit is filled with water;

[0010] The upward stage is from the filling of the primary circuit to the completion of loading, including water purification after the primary circuit is filled with water, water purification of the reactor pool before loading, and whether the turbidity of the reactor pool water meets the loading condition judgment criteria.

[0011] The centralized peeling and purification of the corrosion products of the 80°C platform in the first-loop in the downward stage is to add excessive hydrogen peroxide to the first-loop coolant after the first-loop coolant is cooled to 80°C, so that the dissolved oxygen in the first-loop coolant is greater than 1mg / kg, and the first-loop coolant is changed from a reducing environment to an oxidizing environment, so that the corrosion products on the surface of the core and the first-loop system equipment are quickly oxidized, peeled off and dissolved, and the peeled corrosion products are centralized filtered and purified by the first-loop system purification unit; it is expected that the main pump will be stopped after the first-loop coolant is purified to a turbidity of less than 0.2NTU, so that the corrosion products are completely purified.

[0012] The reactor pool inspection before filling with water in the downlink phase is to inspect the bottom of the reactor pool before the reactor pool is filled with water before unloading to see whether there are any impurities such as chemicals and grease left during the maintenance work that cause turbid water after the reactor pool is filled with water.

[0013] The water purification after the reactor pool is filled with water in the downlink stage is to prepare the reactor pool purification unit for online operation in advance before the reactor pool is filled with water, so that the reactor pool purification unit can be put into operation in time to purify the water quality of the pool after the reactor pool is filled with water, so that the water quality of the reactor pool meets the unloading conditions as soon as possible.

[0014] The criterion for judging whether the turbidity of the reactor pool water quality meets the unloading conditions in the downward stage is that after the reactor pool is filled with water, the pool light gun is turned on to illuminate the upper tube seats of the fuel assemblies in the pressure vessel at the bottom of the pool, and whether the upper tube seats of the fuel assemblies can be visually seen is used as the criterion for judging whether the reactor pool water quality meets the unloading conditions.

[0015] The refueling water tank purification at the low water level stage is to purify the water quality of the refueling water tank after the first-loop coolant is discharged to the refueling water tank for storage after the unloading is completed. It is expected that the turbidity of the water quality in the refueling water tank will be purified to less than 0.1NTU to ensure that the water source for filling the reactor pool is clear before loading.

[0016] The inspection of the reactor pool before the primary circuit is filled with water in the low water level stage is to check the bottom of the reactor pool before the primary circuit system is filled with water before loading to see whether there are any impurities such as chemicals and grease left during the maintenance work that cause turbid water after the reactor pool is filled with water.

[0017] The water quality purification of the primary-loop water filling in the upward stage is that after the primary-loop system is filled with water after the low-water-level maintenance, the corrosion products deposited in the primary-loop system pipeline or the impurities remaining during the maintenance will be stirred up, making the water quality of the primary-loop system turbid after the water filling; in order to alleviate the turbidity of the water quality of the reactor water pool caused by the turbidity of the primary-loop system in the subsequent reactor water pool filling, the primary-loop purification unit is put into operation in time after the primary-loop system is filled with water to purify the primary-loop water quality.

[0018] The water quality purification of the reactor pool before loading in the upward stage is to prepare the reactor pool purification unit for online operation in advance before the reactor pool is filled with water, and after the reactor pool is filled with water to a water level exceeding the reactor pool purification unit pump suction inlet, the reactor pool purification unit is promptly put into operation to purify the pool water quality.

[0019] The criterion for judging whether the turbidity of the water quality of the reactor pool in the upward stage meets the loading conditions is that after the reactor pool is filled with water, the pool light gun is turned on to illuminate the lower grid plate pins in the lower part of the pressure vessel at the bottom of the pool, and whether the lower grid plate pins can be visually seen is used as the criterion for judging whether the water quality of the reactor pool meets the loading conditions.

[0020] The beneficial effects achieved by the present invention are:

[0021] Formulate corresponding control indicators for chemical parameters of systems related to reactor pool water quality at various stages during the overhaul of the unit to achieve front-end control;

[0022] Define an intuitive criterion for judging whether the reactor pool water turbidity meets the loading / unloading conditions, so as to avoid the loading / unloading staff judging whether the water quality affects the loading / unloading operation based on their personal subjective visual turbidity of the pool;

[0023] Adding a reactor pool inspection before filling the reactor pool with water before loading / unloading can effectively prevent the impact of residual chemicals, grease and other impurities on water turbidity during maintenance work;

[0024] Make good preparations for the purification unit before commissioning to ensure that the purification unit can be put into operation to purify water as soon as possible after meeting the commissioning conditions, maximize the water purification time, and improve water turbidity;

[0025] Based on the existing plan to fill the reactor pool with water before loading in the upward phase, an innovative proposal is made to put the purification unit into operation immediately after the reactor pool is filled with water to a water level that meets the suction port of the purification unit pump, thereby greatly improving the purification effect of the reactor pool purification unit; and to rationally utilize the filling time to simultaneously achieve water purification, thereby additionally increasing the purification time. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the reactor pool turbidity control process before loading and unloading for nuclear power plant overhaul;

[0027] Figure 2 This is a schematic diagram of the primary circuit system structure of a nuclear power plant;

[0028] In the figure, 1. ion exchange resin bed; 2. pump; 3. filter; 4. dosing tank. DETAILED DESCRIPTION

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

[0030] A method for controlling turbidity of a reactor pool before overhaul loading and unloading of a nuclear power plant performs front-end control of all aspects of work related to the water quality of the reactor pool from the unit refueling overhaul preparation stage, the down stage, the low-low water level stage, and the up stage.

[0031] The preparation stage is to purify the refueling water tank before the reactor pool is unloaded before the unit refueling overhaul, and it is expected that the turbidity of the refueling water tank will be less than 0.1NTU to ensure that the reactor pool water source is clear before unloading.

[0032] The down stage is from the purification of the 80℃ platform of the primary circuit of the unit overhaul to the completion of unloading. It mainly includes the centralized peeling and purification of the corrosion products of the 80℃ platform of the primary circuit, the inspection of the reactor pool before filling the reactor pool, the purification of the water quality after the reactor pool is filled with water, and whether the turbidity of the reactor pool water meets the unloading condition judgment criteria.

[0033] The low-low water level stage is from the time when the unloading is completed and the primary circuit coolant (i.e., boron-containing water) is discharged to the refueling water tank to the time when the low-low water level maintenance is completed and before the primary circuit system is filled with water. It mainly includes the purification of the refueling water tank and the inspection of the reactor water pool before the primary circuit is filled with water.

[0034] The upward stage is from the primary circuit filling to the completion of loading, which mainly includes water purification after the primary circuit filling, water purification of the reactor pool filling before loading, and whether the turbidity of the reactor pool water meets the loading condition judgment criteria.

[0035] Furthermore, the centralized peeling and purification of the corrosion products of the 80°C platform in the first-loop in the downward stage is that after the first-loop coolant is cooled to 80°C, an excess of hydrogen peroxide is added to the first-loop coolant to make the dissolved oxygen in the first-loop coolant greater than 1 mg / kg, and the first-loop coolant is changed from a reducing environment to an oxidizing environment, so that the corrosion products on the surface of the core and the first-loop system equipment are quickly oxidized, peeled off and dissolved, and the peeled corrosion products are centralized filtered and purified by the first-loop system purification unit; in order to avoid the corrosion products of the 80°C platform first-loop system from being concentratedly peeled off and not thoroughly purified, resulting in the deposition of corrosion products in the first-loop system pipeline and causing turbid water quality after the first loop is filled with water in the upward stage due to the shutdown of the main pump, it is expected that the main pump will be shut down after the first-loop coolant is purified to a turbidity of less than 0.2NTU, so as to purify the corrosion products as thoroughly as possible.

[0036] Furthermore, the reactor pool inspection before filling the reactor pool in the downlink phase is to inspect the bottom of the reactor pool before the reactor pool is about to be filled with water before unloading to check whether there are any impurities such as chemicals, grease, etc. remaining during the maintenance work that may cause turbidity in the water after the reactor pool is filled with water.

[0037] Furthermore, in the said downlink stage, the water purification after the reactor pool is filled with water is to prepare the reactor pool purification unit for online operation in advance before the reactor pool is filled with water, so that the reactor pool purification unit can be put into operation in time to purify the water quality of the pool after the reactor pool is filled with water, so that the water quality of the reactor pool meets the unloading conditions as soon as possible.

[0038] Furthermore, the criterion for judging whether the turbidity of the water quality of the reactor pool meets the unloading conditions in the descending stage is that after the reactor pool is filled with water, the water pool light gun is turned on to illuminate the upper tube seats of the fuel assemblies in the pressure vessel at the bottom of the water pool, and whether the upper tube seats of the fuel assemblies can be visually seen is used as the criterion for judging whether the water quality of the reactor pool meets the unloading conditions.

[0039] Furthermore, the refueling water tank purification in the low water level stage is to purify the water quality of the refueling water tank after the first-loop coolant is discharged to the refueling water tank for storage at the end of unloading, and it is expected to be purified to the turbidity of the water quality in the refueling water tank <0.1NTU to ensure that the water source for filling the reactor pool is clear before loading.

[0040] Furthermore, the inspection of the reactor pool before the primary circuit is filled with water in the low water level stage is to inspect the bottom of the reactor pool before the primary circuit system is about to be filled with water before loading to see whether there are any impurities such as chemicals, grease, etc. remaining during the maintenance work that may cause turbid water after the reactor pool is filled with water.

[0041] Furthermore, the water quality purification of the primary-loop water filling in the upward stage is after the primary-loop system is filled with water after the low-water-level maintenance, which will stir up the corrosion products deposited in the primary-loop system pipeline or the impurities remaining during the maintenance, making the water quality of the primary-loop system turbid after the water filling; in order to alleviate the turbidity of the water quality of the reactor water pool caused by the turbidity of the primary-loop system in the subsequent reactor water pool filling, it is necessary to put the primary-loop purification unit into operation in time after the primary-loop system is filled with water to purify the primary-loop water quality.

[0042] Furthermore, the water quality purification of the reactor pool water filling before loading in the upward stage is to prepare the reactor pool purification unit for online operation in advance before the reactor pool is filled with water, and to put the reactor pool purification unit into operation in time to purify the water quality of the pool after the reactor pool is filled with water to a water level exceeding the suction port of the reactor pool purification unit pump. Putting the purification unit into operation as early as possible when the water level of the reactor pool is as low as possible can maximize the purification effect of the reactor pool purification unit; secondly, after putting the reactor pool purification unit into operation in advance, it can also be purified while filling the water during the subsequent reactor pool filling, and the water quality purification can be achieved synchronously by rationally utilizing the filling time, so that the water quality of the reactor pool can meet the loading conditions as early as possible.

[0043] Furthermore, the criterion for judging whether the turbidity of the water quality of the reactor pool in the upward stage meets the loading conditions is that after the reactor pool is filled with water, the water pool light gun is turned on to illuminate the lower grid plate pins in the lower part of the pressure vessel at the bottom of the water pool, and whether the lower grid plate pins can be visually seen is used as the criterion for judging whether the water quality of the reactor pool meets the loading conditions.

[0044] The present invention discloses a method for controlling reactor water pool turbidity before overhaul loading and unloading of a nuclear power plant, which comprehensively controls the work related to the reactor water pool water quality, thereby achieving the purpose of controlling the turbidity of the reactor water pool before loading / unloading and preventing it from affecting the normal progress of loading / unloading work.

[0045] The key points and protection points of the present invention are:

[0046] A method for controlling the turbidity of a reactor pool before overhaul loading and unloading of a nuclear power plant is provided, which performs front-end control on all aspects of work related to the water quality of the reactor pool from the unit refueling overhaul preparation stage, the down stage, the low-low water level stage, and the up stage, and mainly includes:

[0047] Formulate corresponding control indicators for chemical parameters of systems related to reactor pool water quality at various stages during the overhaul of the unit to achieve front-end control;

[0048] Define an intuitive criterion for judging whether the reactor pool water turbidity meets the loading / unloading conditions, so as to avoid the loading / unloading staff judging whether the water quality affects the loading / unloading operation based on their personal subjective visual turbidity of the pool;

[0049] Adding a reactor pool inspection before filling the reactor pool with water before loading / unloading can effectively prevent the impact of residual chemicals, grease and other impurities on water turbidity during maintenance work;

[0050] Make good preparations for the purification unit before commissioning to ensure that the purification unit can be put into operation to purify water as soon as possible after meeting the commissioning conditions, maximize the water purification time, and improve water turbidity;

[0051] Based on the existing plan to fill the reactor pool with water before loading in the upward phase, an innovative proposal is made to put the purification unit into operation immediately after the reactor pool is filled with water to a water level that meets the suction port of the purification unit pump, thereby greatly improving the purification effect of the reactor pool purification unit; and to rationally utilize the filling time to simultaneously achieve water purification, thereby additionally increasing the purification time.

[0052] 1. Before the unit overhaul, the refueling water tank should be purified to a turbidity level of <

[0053] 0.1NTU, ensuring that the water source for filling the reactor pool is clear before unloading.

[0054] 2. After the temperature of the primary coolant in the unit drops to 80°C during overhaul, the primary coolant purification unit is removed; then 15L of 35% hydrogen peroxide is added to the primary coolant, and the dissolved oxygen in the primary coolant is tested. After confirming that the dissolved oxygen is greater than 1mg / kg, the primary coolant purification unit is put back into operation to centrally filter and purify the corrosion products shed by oxidation to reduce the turbidity of the primary coolant.

[0055] 3. Check whether the purification efficiency of the primary coolant purification unit meets the requirements. If the filter pressure difference in the purification unit exceeds 0.25MPa, the filter is invalid and needs to be replaced; if the outlet Co-58 of the ion exchange resin bed in the purification unit is greater than 1000MBq / t and the Co-58 purification efficiency is less than 90% or the high pressure difference affects the operation, use the spare ion exchange resin bed for purification.

[0056] 4. In order to avoid the main pump being shut down when the corrosion products of the primary circuit system of the 80℃ platform are concentratedly peeled off and not thoroughly purified, causing the corrosion products to be deposited in the primary circuit system pipeline, resulting in turbid water after the primary circuit is filled with water in the upward stage, it is expected that the main pump will be shut down after the primary circuit coolant is purified to a turbidity of <0.2NTU.

[0057] 5. Before unloading and before the reactor pool is about to be filled with water, check the bottom of the reactor pool to see if there are any chemicals, grease, etc. remaining during the maintenance work. If so, contact the cleaning staff to clean it up to avoid residual chemicals, grease and other impurities causing turbid water after the reactor pool is filled with water.

[0058] 6. Before the reactor pool is about to be filled with water before unloading, the reactor pool purification unit should be put online in advance. After the reactor pool is filled with water, the reactor pool purification unit should be put into operation as soon as possible to purify the pool water quality.

[0059] 7. After the reactor pool is filled with water, turn on the reactor pool light gun to illuminate the upper tube sockets of the fuel assemblies in the pressure vessel at the bottom of the pool. If the upper tube sockets of the fuel assemblies are clearly visible, the water quality of the reactor pool has met the unloading conditions and the unloading operation can be performed. If the upper tube sockets of the fuel assemblies are not clearly visible, continue to purify the reactor pool water until the upper tube sockets of the fuel assemblies are clearly visible.

[0060] 8. After the unloading is completed, the primary coolant is discharged to the refueling water tank for storage, and the water quality of the refueling water tank is purified. It is expected that the turbidity of the water quality in the refueling water tank will be purified to less than 0.1NTU to ensure that the water source for filling the reactor pool is clear before loading.

[0061] 9. Before the primary loop system is filled with water before loading, check the bottom of the reactor pool to see if there are any chemicals, grease, etc. remaining during the maintenance work. If so, contact the cleaning staff to clean it up to avoid residual chemicals, grease and other impurities causing turbid water after the reactor pool is filled with water.

[0062] 10. After the primary circuit system is filled with water, the primary circuit coolant purification unit shall be put into operation in time to purify the primary circuit coolant.

[0063] 11. Before filling the reactor pool with water before loading, the reactor pool purification unit should be put online in advance. After the reactor pool is filled with water to a level exceeding the suction port of the reactor pool purification unit pump, the reactor pool purification unit should be put into operation as soon as possible to purify the pool water quality; maximize the purification effect of the reactor pool purification unit, and rationally utilize the filling time to simultaneously achieve water purification, thereby increasing the purification time.

[0064] 12. After the reactor pool is filled with water, turn on the reactor pool light gun to illuminate the lower grid plate pins in the pressure vessel at the bottom of the pool. If the lower grid plate pins are clearly visible, the reactor pool water quality has met the loading conditions and the loading operation can be performed; if the lower grid plate pins are not clearly visible, continue to purify the reactor pool water quality until the lower grid plate pins are clearly visible.

Claims

1. A method for controlling turbidity in a reactor pool before loading and unloading in a nuclear power plant overhaul, characterized in that: Carry out front-end control of work related to reactor pool water quality from the unit refueling overhaul preparation stage, down stage, low-low water level stage, and up stage; The preparation stage is to purify the refueling water tank of the reactor pool before unloading before the unit refueling overhaul, and it is expected that the turbidity of the refueling water tank will be less than 0.1NTU to ensure that the water source for filling the reactor pool is clear before unloading; The down stage is from the purification of the 80°C platform of the primary circuit of the unit overhaul to the completion of unloading, including the centralized peeling and purification of the corrosion products of the 80°C platform of the primary circuit, the inspection of the reactor pool before filling the reactor pool with water, the purification of the water quality of the reactor pool after filling the reactor pool with water, and whether the turbidity of the water quality of the reactor pool meets the unloading condition judgment criteria; The low-low water level stage is from the time when the unloading is completed and the primary circuit coolant is discharged to the refueling water tank to the time when the low-low water level maintenance is completed and before the primary circuit system is filled with water, including the refueling water tank purification and the reactor water pool inspection before the primary circuit is filled with water; The upward stage is from the filling of the primary circuit to the completion of loading, including water purification after the primary circuit is filled with water, water purification of the reactor pool before loading, and whether the turbidity of the reactor pool water meets the loading condition judgment criteria.

2. The method for controlling turbidity of a reactor pool before overhaul loading and unloading of a nuclear power plant according to claim 1, characterized in that: The centralized peeling and purification of the corrosion products of the 80°C platform in the first-loop in the downward stage is to add excessive hydrogen peroxide to the first-loop coolant after the first-loop coolant is cooled to 80°C, so that the dissolved oxygen in the first-loop coolant is greater than 1mg / kg, and the first-loop coolant is changed from a reducing environment to an oxidizing environment, so that the corrosion products on the surface of the core and the first-loop system equipment are quickly oxidized, peeled off and dissolved, and the peeled corrosion products are centralized filtered and purified by the first-loop system purification unit; it is expected that the main pump will be stopped after the first-loop coolant is purified to a turbidity of less than 0.2NTU, so that the corrosion products are completely purified.

3. The method for controlling turbidity of a reactor pool before loading and unloading of a nuclear power plant during overhaul according to claim 1, characterized in that: The reactor pool inspection before filling with water in the downlink phase is to inspect the bottom of the reactor pool before the reactor pool is filled with water before unloading to see whether there are any impurities such as chemicals and grease left during the maintenance work that cause turbid water after the reactor pool is filled with water.

4. The method for controlling turbidity of a reactor pool before loading and unloading of a nuclear power plant during overhaul according to claim 1, characterized in that: The water purification after the reactor pool is filled with water in the downlink stage is to prepare the reactor pool purification unit for online operation in advance before the reactor pool is filled with water, so that the reactor pool purification unit can be put into operation in time to purify the water quality of the pool after the reactor pool is filled with water, so that the water quality of the reactor pool meets the unloading conditions as soon as possible.

5. The method for controlling turbidity of a reactor pool before overhaul loading and unloading of a nuclear power plant according to claim 1, characterized in that: The criterion for judging whether the turbidity of the reactor pool water quality meets the unloading conditions in the downward stage is that after the reactor pool is filled with water, the pool light gun is turned on to illuminate the upper tube seats of the fuel assemblies in the pressure vessel at the bottom of the pool, and whether the upper tube seats of the fuel assemblies can be visually seen is used as the criterion for judging whether the reactor pool water quality meets the unloading conditions.

6. The method for controlling turbidity in a reactor pool before loading and unloading of a nuclear power plant during overhaul according to claim 1, characterized in that: The refueling water tank purification at the low water level stage is to purify the water quality of the refueling water tank after the first-loop coolant is discharged to the refueling water tank for storage after the unloading is completed. It is expected that the turbidity of the water quality in the refueling water tank will be purified to less than 0.1NTU to ensure that the water source for filling the reactor pool is clear before loading.

7. The method for controlling turbidity in a reactor pool before loading and unloading of a nuclear power plant during overhaul according to claim 1, characterized in that: The inspection of the reactor pool before the primary circuit is filled with water in the low water level stage is to check the bottom of the reactor pool before the primary circuit system is filled with water before loading to see whether there are any impurities such as chemicals and grease left during the maintenance work that cause turbid water after the reactor pool is filled with water.

8. The method for controlling turbidity of a reactor pool before loading and unloading of a nuclear power plant during overhaul according to claim 1, characterized in that: The water quality purification of the primary-loop water filling in the upward stage is that after the primary-loop system is filled with water after the low-water-level maintenance, the corrosion products deposited in the primary-loop system pipeline or the impurities remaining during the maintenance will be stirred up, making the water quality of the primary-loop system turbid after the water filling; in order to alleviate the turbidity of the water quality of the reactor water pool caused by the turbidity of the primary-loop system in the subsequent reactor water pool filling, the primary-loop purification unit is put into operation in time after the primary-loop system is filled with water to purify the primary-loop water quality.

9. The method for controlling turbidity in a reactor pool before loading and unloading in a nuclear power plant overhaul according to claim 1, characterized in that: The water quality purification of the reactor pool before loading in the upward stage is to prepare the reactor pool purification unit for online operation in advance before the reactor pool is filled with water, and after the reactor pool is filled with water to a water level exceeding the reactor pool purification unit pump suction inlet, the reactor pool purification unit is promptly put into operation to purify the pool water quality.

10. The method for controlling turbidity of a reactor pool before loading and unloading of a nuclear power plant during overhaul according to claim 1, characterized in that: The criterion for judging whether the turbidity of the water quality of the reactor pool in the upward stage meets the loading conditions is that after the reactor pool is filled with water, the pool light gun is turned on to illuminate the lower grid plate pins in the lower part of the pressure vessel at the bottom of the pool, and whether the lower grid plate pins can be visually seen is used as the criterion for judging whether the water quality of the reactor pool meets the loading conditions.

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