Chemical control method and system during overhaul shutdown period of unit when reactor core part of nuclear power station is damaged

Abstract

The invention relates to a chemical control method and system in a unit overhaul shutdown period when reactor core components of a nuclear power station are damaged. The chemical control method comprises the following steps: determining the damage type of the reactor core components; if the damage type of the reactor core part is fuel damage, performing preparation before overhaul of the fuel damage unit, and after the preparation before overhaul is completed, performing chemical control in the descending period of overhaul of the fuel damage unit; and if the damage type of the reactor core part is neutron source damage, executing preparation before overhaul of a neutron source damage unit, and after the preparation before overhaul is completed, executing chemical control in an overhaul descending period of the neutron source damage unit. According to the method, chemical control can be carried out on a unit with fuel damage or neutron source damage in the overhaul descending period, dosage rising caused by deposition or unfavorable removal control is avoided, and the overhaul period can be prevented from being delayed.

Description

Technical Field

[0001] The present invention relates to the technical field of pressurized water reactor nuclear power plants, and more particularly to a chemical control method and system during the overhaul shutdown of a unit when a core component of a nuclear power plant is damaged. Background Art

[0002] After a nuclear power plant was started for an overhaul, monitoring found that the fissile nuclides in the primary circuit had increased. After sampling and analysis and joint diagnosis of multiple professionals, it was found that there was a fuel damage defect. After analyzing the data of Xe-133 and I-131 in the primary circuit during the operation of the unit, it was found that a corresponding chemical control plan needed to be formulated to avoid a large amount of radioactive release that would cause the power plant radiation monitoring system (KRT system) to alarm, and also to avoid irradiation or internal contamination of personnel. This is a problem that has never occurred before. In the overhaul, the formulation of a more appropriate chemical control plan needs to consider the preparation before the overhaul, the control of the shutdown process, and the control of the startup process.

[0003] The gamma spectrum of a unit in a power station detected radioactive Sb-122 and Sb-124 (antimony) in the main circuit. After many discussions, it was determined that the secondary neutron source rod was damaged. The damage to the secondary neutron source rod caused the increase of radioactive nuclides Sb-122 and Sb-124 in the main circuit, and the antimony element can only be effectively removed through oxidation purification during the overhaul. Subsequently, the power station formulated a control plan for the daily period, and decided to closely monitor the radioactivity of the main circuit during the daily period, and purify the antimony element during the overhaul. Antimony nuclides exist in the form of particles or colloids during normal power operation (pH is about 7). The only way to remove antimony nuclides during the daily period is through filters, and the purification of the desalination bed can only play the role of a filter. Only by converting the particle or colloidal state of antimony into ionic state through oxidation purification during the overhaul can it be effectively removed through the desalination bed. Therefore, it is also necessary to chemically control the damage of the neutron source during the downtime of the unit overhaul. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a chemical control method and system during the overhaul shutdown of a nuclear power plant unit when the core components are damaged, in view of the problems existing in the prior art.

[0005] The technical solution adopted by the present invention to solve the technical problem is to construct a chemical control method during the overhaul shutdown of a damaged unit in a nuclear power plant, comprising the following steps:

[0006] Determining the damage type of the core component; the damage type of the core component includes: fuel damage or neutron source damage;

[0007] If the damage type of the core component is fuel damage, pre-overhaul preparation for the fuel damaged unit is performed, and after the pre-overhaul preparation is completed, chemical control during the overhaul downtime of the fuel damaged unit is performed;

[0008] If the damage type of the core component is neutron source damage, pre-overhaul preparation for the unit with damaged neutron source is performed, and after the pre-overhaul preparation is completed, chemical control during the overhaul downtime of the unit with damaged neutron source is performed.

[0009] In the chemical control method during the overhaul shutdown of a unit when a core component of a nuclear power plant is damaged according to the present invention, if the type of damage to the unit is fuel damage, performing pre-overhaul preparations for the fuel damaged unit includes:

[0010] Preparation 2 months before the overhaul;

[0011] Preparations 15 to 7 days before executing subcriticality;

[0012] Preparation 7 days to 24 hours before executing subcriticality;

[0013] Preparation 24 hours before execution of critical;

[0014] Determine whether the xenon-iodine control target before load reduction is met. If so, complete the pre-overhaul preparation for the fuel-damaged unit;

[0015] If the xenon-iodine control target before load reduction is not met, continue to perform the preparation for the 24 hours before criticality.

[0016] In the chemical control method for nuclear power plant unit overhaul shutdown when core components are damaged according to the present invention, the preparations 2 months before the overhaul include:

[0017] Make sure the desalination bed is efficient, the filter pore size is 0.45 mm, and there are enough spare parts;

[0018] The preparations for the 15 to 7 days before the implementation of subcriticality include:

[0019] Verify the purification of the refueling water tank and the commissioning of the scavenging pipeline;

[0020] Confirm that the second orifice plate of the chemical and volume control system is in operation;

[0021] Sampling and analyzing the air in nuclear reactor buildings;

[0022] The preparations 7 days to 24 hours before executing subcriticality include:

[0023] Control volume and control box hydrogen purge;

[0024] Connecting the gas phase of the pressurizer of the reactor cooler system to the front storage tank of the boron recovery system to perform pressurizer gas phase scavenging;

[0025] Execute the discharge application of the atmosphere monitoring system in the containment;

[0026] The preparations for the critical 24 hours before execution include:

[0027] Continue to purge the pressurizer gas phase by connecting the gas phase of the reactor cooler system pressurizer to the front storage tank of the boron recovery system;

[0028] Switch the chemical and volume control system tanks to nitrogen blanketing;

[0029] Lithium addition control is based on I-131 activity.

[0030] In the chemical control method during overhaul shutdown of a unit when a core component of a nuclear power plant is damaged according to the present invention, if the type of damage to the core component is neutron source damage, performing pre-overhaul preparations for the unit with a damaged neutron source includes:

[0031] Preparation 2 months before the overhaul;

[0032] Preparations 15 to 7 days before executing subcriticality;

[0033] Preparation 7 days to 24 hours before executing subcriticality;

[0034] Preparation 24 hours before execution of critical;

[0035] Determine whether the xenon-iodine control target before load reduction is met. If so, complete the pre-overhaul preparation for the damaged neutron source unit;

[0036] If the xenon-iodine control target before load reduction is not met, continue to perform the preparation for the 24 hours before criticality.

[0037] In the chemical control method for nuclear power plant unit overhaul shutdown when core components are damaged according to the present invention, the preparations 2 months before the overhaul include:

[0038] Make sure the desalination bed is efficient, the filter pore size is 0.45 mm, and there are enough spare parts;

[0039] The preparations for the 15 to 7 days before the implementation of subcriticality include:

[0040] Verify the purification of the refueling water tank and the commissioning of the scavenging pipeline;

[0041] Confirm that the second orifice plate of the chemical and volume control system is in operation;

[0042] Sampling and analyzing the air in nuclear reactor buildings;

[0043] The preparations 7 days to 24 hours before executing subcriticality include:

[0044] Control volume and control box hydrogen purge;

[0045] Connecting the gas phase of the pressurizer of the reactor cooler system to the front storage tank of the boron recovery system to perform pressurizer gas phase scavenging;

[0046] Execute the discharge application of the atmosphere monitoring system in the containment;

[0047] The preparations for the critical 24 hours before execution include:

[0048] Continue to purge the pressurizer gas phase by connecting the gas phase of the reactor cooler system pressurizer to the front storage tank of the boron recovery system;

[0049] Switch the chemical and volume control system tanks to nitrogen blanketing;

[0050] Lithium addition control is based on I-131 activity.

[0051] In the chemical control method during the overhaul shutdown of a nuclear power plant unit when a core component is damaged according to the present invention, the chemical control during the downtime of the overhaul of the fuel damaged unit includes:

[0052] Execute control 1 hour before subcriticality;

[0053] Execute post-subcritical hot stop platform control;

[0054] After executing the hot shutdown platform, the residual heat removal system is connected, and it is determined whether the xenon-iodine control target and the steam cavity flooding radioactivity control target before the residual heat removal system is connected are met;

[0055] If it is satisfied, the steam cavity flooding is executed, and after the steam cavity flooding is completed, it is determined whether the rapid cooling control specification is met;

[0056] If the rapid cooling control specification is met, rapid cooling is performed;

[0057] If the main pump shutdown conditions are met, the main pump shutdown is executed;

[0058] If the radioactive operation control conditions are met, the 25bar-pressure regulator manhole is opened;

[0059] Determine whether the radioactivity control values ​​for opening the main cover and filling the reactor pool are met;

[0060] If the radioactivity control values ​​for opening the main cover and filling the reactor pool with water are met, unloading is started.

[0061] In the chemical control method during the overhaul shutdown of the unit when the core component of the nuclear power plant is damaged according to the present invention, the xenon-iodine control target and the radioactivity control target before the residual heat removal system is connected include:

[0062] The xenon-iodine control targets before the waste heat removal system is connected are: Xe-133<4000MBq / t, I-131<2000MBq / t;

[0063] The steam cavity flooding radioactivity control targets are: Xe-133 <4000MBq / t, I-131 <2000MBq / t;

[0064] The rapid cooling control specification is: Xe-133<4000MBq / t, I-131<2000MBq / t;

[0065] The main pump shutdown control conditions are: Xe-133<4000MBq / t, I-131<100MBq / t, Ag-110m<4000MBq / t, Co-58<25000MBq / t, total γ<25000MBq / t;

[0066] The opening conditions are: Xe-133<1500MBq / t, I-131<100MBq / t;

[0067] The radioactivity control values ​​of the conditions for opening the large cover and filling the reactor pool with water are: Xe-133<4000MBq / t, I-131<100MBq / t, Co-58<2000MBq / t, expected value<4000MBq / t, and total γ<4000MBq / t.

[0068] In the method for chemical control during the overhaul shutdown of a unit when a core component of a nuclear power plant is damaged according to the present invention, the chemical control during the downtime of the overhaul of the unit when a neutron source is damaged comprises:

[0069] Execute control 1 hour before subcriticality;

[0070] Execute post-subcritical hot stop platform control;

[0071] After executing the hot shutdown platform, the residual heat removal system is connected, and it is determined whether the xenon-iodine control target, steam cavity flooding radioactivity control target and containment ventilation system commissioning conditions before the residual heat removal system is connected are met;

[0072] If it is satisfied, the steam cavity flooding is executed, and after the steam cavity flooding is completed, it is determined whether the rapid cooling control specification is met;

[0073] If the rapid cooling control specification is met, rapid cooling is performed;

[0074] If the main pump shutdown conditions are met, the main pump shutdown is executed;

[0075] If the radioactive operation control conditions are met, the 25bar-pressure regulator manhole is opened;

[0076] Determine whether the radioactivity control values ​​for opening the large cover and filling the reactor pool are met;

[0077] If the radioactivity control values ​​for opening the main cover and filling the reactor pool with water are met, unloading is started.

[0078] In the chemical control method during the overhaul shutdown of the unit when the core component of the nuclear power plant is damaged according to the present invention, the xenon-iodine control target before the connection of the residual heat removal system is: Xe-133<4000MBq / t, I-131<2000MBq / t;

[0079] The steam cavity flooding radioactivity control targets are: Xe-133 <4000MBq / t, I-131 <2000MBq / t;

[0080] The operation conditions of the containment ventilation system are: I-131eq < 4400MBq / t, KRT009MA < 4.0MBq / m 3 ;

[0081] The rapid cooling control specification is: Xe-133<4000MBq / t, I-131<2000MBq / t;

[0082] The main pump shutdown control condition includes: a first operation control condition and a second operation control condition;

[0083] The first operating control conditions are: γt<50000MBq / t, Xe-133<15000MBq / t, I-131<100MBq / t, Ag-110m<4000MBq / t, Co-58<25000MBq / t, Sb-124<4000MBq / t;

[0084] The second operation control conditions are: γt<50000MBq / t, Xe-133<15000MBq / t, I-131<100MBq / t, Ag-110m<4000MBq / t, Co-58+Sb-124<25000MBq / t, Sb-124<4000MBq / t;

[0085] The conditions after opening the hole are: Xe-133<1500MBq / t, I-131<100MBq / t;

[0086] The radioactivity control values ​​under the conditions of opening the large cover and filling the reactor pool with water are: Xe-133<1000MBq / t, I-131<50MBq / t, Co-58<2000MBq / t, expected value<1000MBq / t, and total γ<4000MBq / t.

[0087] The present invention also provides a chemical control system during the overhaul shutdown of a nuclear power plant unit when a core component is damaged, comprising:

[0088] A damage type determination unit, used to determine the damage type of a core component; the damage type of the core component includes: fuel damage or neutron source damage;

[0089] A fuel damage chemical control unit, for executing pre-overhaul preparations for the fuel-damaged unit if the damage type of the core component is fuel damage, and executing chemical control during the downtime of the overhaul of the fuel-damaged unit after the pre-overhaul preparations are completed;

[0090] The neutron source damage chemical control unit is used to perform pre-overhaul preparation of the neutron source damaged unit if the damage type of the core component is neutron source damage, and after the pre-overhaul preparation is completed, perform chemical control during the overhaul downtime of the neutron source damaged unit.

[0091] The chemical control method and system for nuclear power plant core component damage during the overhaul shutdown of the unit has the following beneficial effects: including the following steps: determining the type of core component damage; if the core component damage type is fuel damage, executing the pre-overhaul preparation of the fuel damaged unit, and after the pre-overhaul preparation is completed, executing the chemical control during the overhaul downtime of the fuel damaged unit; if the core component damage type is neutron source damage, executing the pre-overhaul preparation of the neutron source damaged unit, and after the pre-overhaul preparation is completed, executing the chemical control during the overhaul downtime of the neutron source damaged unit. The present invention can perform chemical control on the fuel damaged or neutron source damaged unit during the overhaul downtime, avoid deposition or removal control caused by unfavorable dose increase, and avoid delaying the overhaul period. BRIEF DESCRIPTION OF THE DRAWINGS

[0092] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0093] Figure 1 It is a flow chart of a chemical control method provided by the present invention during the shutdown period of a nuclear power plant unit overhaul when a core component is damaged;

[0094] Figure 2 It is a schematic flow diagram of chemical control during the downtime of a fuel damaged unit provided by the present invention;

[0095] Figure 3 It is a schematic flow diagram of chemical control during the neutron source damage downward period provided by the present invention;

[0096] Figure 4 The invention provides a principle block diagram of a chemical control system during a shutdown period for overhaul of a nuclear power plant unit when a core component of the nuclear power plant is damaged. DETAILED DESCRIPTION

[0097] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0098] refer to Figure 1 , Figure 1 The present invention provides a flow chart of a chemical control method during unit overhaul shutdown when a core component of a nuclear power plant is damaged.

[0099] Specifically, Figure 1 As shown, the chemical control method during the overhaul shutdown of the unit when the core components of the nuclear power plant are damaged includes the following steps:

[0100] Step S101: Determine the damage type of core components.

[0101] Specifically, in the embodiment of the present invention, the types of damage to the core components include: fuel damage or neutron source damage.

[0102] Step S102: If the damage type of the core component is fuel damage, pre-overhaul preparation for the fuel-damaged unit is performed, and after the pre-overhaul preparation is completed, chemical control during the overhaul downtime of the fuel-damaged unit is performed.

[0103] Step S103: If the damage type of the core component is neutron source damage, pre-overhaul preparation for the neutron source damaged unit is performed, and after the pre-overhaul preparation is completed, chemical control during the overhaul downtime of the neutron source damaged unit is performed.

[0104] Specifically, fuel damage and neutron source damage will release a large amount of radioactive substances into the circuit, such as I-131, X-133; Sb-122 and Sb-124, etc., which will inevitably increase the difficulty of unit control and may also cause the unit to withdraw. If it is not well controlled during the overhaul, it may delay the overhaul critical path. At the same time, if the radioactive substances released after the fuel is damaged are not removed sufficiently, it may cause accidental exposure to personnel and cause accidental release of radioactive gases into the environment. The present invention can be used to perform chemical control during the overhaul downtime for units with damaged fuel or neutron source, avoiding the increase in the difficulty of unit control and causing the unit to withdraw, and will not delay the overhaul critical path. It can also avoid accidental exposure to personnel and accidental release of radioactive gases into the environment.

[0105] refer to Figure 2 , Figure 2 Downstream chemical control logic for fuel damaged units.

[0106] Specifically, Figure 2 As shown, if the damage type of the core component is fuel damage, the pre-overhaul preparation for the fuel-damaged unit includes: preparation 2 months before the overhaul; preparation 15 to 7 days before subcriticality; preparation 7 to 24 hours before subcriticality; preparation 24 hours before criticality; judging whether the xenon-iodine control target before load reduction is met, if so, the pre-overhaul preparation for the fuel-damaged unit is completed; if the xenon-iodine control target before load reduction is not met, the preparation 24 hours before criticality is continued. Among them, the xenon-iodine control target before load reduction is: Xe-133<8000MBq / t, I-131<2000MBq / t.

[0107] In the embodiment of the present invention, the preparations for 2 months before the overhaul include: confirming that the efficiency of the desalting bed is normal, the filter aperture is 0.45 mm, and there are sufficient spare parts. The preparations for 15 to 7 days before subcriticality include: verifying the purification of the refueling water tank and the commissioning of the scavenging pipeline; verifying that the second orifice plate of the chemical and volumetric control system has been put into operation; and sampling and analyzing the air in the nuclear reactor building. The preparations for 7 days to 24 hours before subcriticality include: controlling the hydrogen purge of the control box; connecting the gas phase of the pressurizer of the reactor cooler system to the front storage tank of the boron recovery system to perform the gas phase purge of the pressurizer; and executing the emission application of the atmosphere monitoring system in the containment. The preparations for 24 hours before criticality include: continuing to purge the pressurizer gas phase by connecting the gas phase of the pressurizer of the reactor cooler system to the front storage tank of the boron recovery system; switching the chemical and volumetric control system control box to nitrogen coverage; and performing lithium addition control based on the activity of I-131.

[0108] like Figure 2 As shown, the chemical control during the downtime of the overhaul of the fuel-damaged unit includes: executing the control for 1 hour before subcriticality; executing the hot shutdown platform control after subcriticality; executing the connection of the residual heat removal system after the hot shutdown platform, and judging whether the xenon-iodine control target before the connection of the residual heat removal system and the steam cavity flooding radioactivity control target are met; if they are met, the steam cavity flooding is executed, and after the steam cavity flooding is completed, it is judged whether the rapid cooling control specification is met; if the rapid cooling control specification is met, rapid cooling is executed; if the main pump shutdown condition is met, the main pump shutdown is executed; if the radioactivity operation control condition is met, the 25bar-regulator manhole is opened; it is judged whether the radioactivity control value of the opening of the large cover and the reactor pool filling condition is met; if the radioactivity control value of the opening of the large cover and the reactor pool filling condition is met, the unloading is started.

[0109] Among them, in the downlink chemical control of the fuel-damaged unit, the xenon-iodine control target and other radioactive control targets before the connection of the residual heat removal system include: the xenon-iodine control target before the connection of the residual heat removal system is: Xe-133<4000MBq / t, I-131<2000MBq / t. The steam cavity flooding radioactive control target is: Xe-133<4000MBq / t, I-131<2000MBq / t. The rapid cooling control specification is: Xe-133<4000MBq / t, I-131<2000MBq / t. The main pump shutdown control conditions are: Xe-133<4000MBq / t, I-131<100MBq / t, Ag-110m<4000MBq / t, Co-58<25000MBq / t, total γ<25000MBq / t. The conditions after opening the hole are: Xe-133 <1500MBq / t, I-131 <100MBq / t. The radioactivity control values ​​of the opening of the large cover and the reactor pool filling conditions are: Xe-133 <4000MBq / t, I-131 <100MBq / t, Co-58 <2000MBq / t, expected value <4000MBq / t, total γ <4000MBq / t.

[0110] like Figure 2 As shown, the chemical control of the fuel damaged unit downlink specifically includes the following steps:

[0111] Step 1: Preparation 2 months before overhaul:

[0112] Verify the efficiency of the desalination bed and determine whether the resin needs to be replaced based on the efficiency. Specifically:

[0113] (1) Evaluate the efficiency of TEP007DE (primary boron removal bed (anion bed)) to prepare for boron removal at the end of its service life;

[0114] (2) Confirm that the desalination bed efficiencies of PTR001DE (spent fuel pool purification desalination bed (mixed bed)), TEP006DE (overhaul of primary circuit purification desalination bed (mixed bed)), TEP002 / 004DE (boron recovery system desalination bed (002DE is a cation bed, 004DE is a mixed bed)), and RCV001 / 002DE (chemical and volume control system desalination bed (mixed bed)) meet the overhaul requirements, otherwise make a replacement plan. Among them, the overhaul requirements are: the desalination bed is not invalid and the efficiency is above 90%.

[0115] Confirm that RCV001FI (chemical and volume control system desalination bed filter), PTR001FI (spent fuel pool filter), PTR003 / 004FI (reactor pool filter) are used in overhaul. 0.45μm pore size filter, and verify whether the number of filter spare parts and the number of replaced filter shielding containers are sufficient. Among them, whether the number of filter shielding containers is sufficient is based on actual application, generally 1 to 2, with sufficient installation as the standard.

[0116] Step 2: Subcritical 15 days to 7 days preparation:

[0117] (1) PTR001BA (refueling water tank) purification before overhaul:

[0118] Before the overhaul, PTR001BA was purified for 48 hours. During and after the purification process, samples were taken for analysis of turbidity, B (boron) turbidity (target value < 0.1 NTU) and γt (total radioactivity) (target value < 10 MBq / t);

[0119] (2) Verify the scavenging pipeline:

[0120] The overhaul plan is included in the plan in advance and verified 15 days before subcriticality;

[0121] 15 days before subcriticality, adjust REN201VP (the isolating valve before the primary heat exchanger on the purge air pipeline of the nuclear sampling system) to a quarter of the opening (generally: first completely close, then idle during the opening process, and rotate a quarter of a turn after the valve is stressed. A major overhaul found that the opening of REN201VP needs to be adjusted several times each time the pipeline is put back into operation), and restore its opening when the primary circuit is depressurized to 40 bar; before opening the purge air pipeline, notify the radiation protection professionals to isolate the relevant rooms and pay attention to the KRT value (specifically: pay attention to whether the KRT reading rises, etc., whether it will exceed its alarm threshold (different KRTs have different alarm thresholds, that is, pay attention to the KRT of the room where the purge air pipeline passes, mainly to prevent pipeline leakage or other accidents), and put the purge air pipeline into operation for 1 hour for verification;

[0122] (3) Confirm the commissioning of the second RCV (chemical and volume control system) orifice plate;

[0123] (4) Fill the tank pool (spent fuel tank storage pool of the reactor water pool and the spent fuel pool cooling and treatment system (PTR)) with water to about 1.5 meters from the top of the pool. After circulation, chemical personnel take samples from the tank pool for boron and anion testing;

[0124] (5) 15 days before the overhaul, sample the RX air (the air in the nuclear reactor building) and evaluate whether the EVF (air purification system in the containment) needs to be put into operation (this sampling is done for CO measurement). According to the ETY sampling and analysis results, determine whether the ETY (atmospheric monitoring system in the containment) low-flow purge needs to be put into operation. Among them, the most recent ETY sampling and analysis results of the containment before the shutdown (iodine box I-131 activity concentration) shall prevail, and refer to the KRT008 / 009 / 028MA value before the EBA is put into operation for judgment. If I-131 is greater than the detection limit, it indicates iodine contamination and the EVF needs to be started; otherwise, there is no iodine contamination and the EVF does not need to be started.

[0125] The 7 days to 24 hours before subcriticality can be divided into three preparation stages: 7 days to 3 days before subcriticality, 72h to 48h before subcriticality, and 48h to 24h before subcriticality. The details are as follows:

[0126] Step 3: Preparation 7 to 3 days before subcriticality:

[0127] (1) 7 days before subcriticality, start the pre-operation of hydrogen purge of the control box. According to the hydrogen content of the primary circuit, arrange to adjust the hydrogen pressure of RCV002BA (chemical and volume control system control box) to 1.4 bar (empirical value);

[0128] (2) 7 days before the overhaul of subcriticality, the PZR-TEP001BA (referring to the down stage of overhaul, connecting the gas phase of the pressurizer of the reactor cooler system to the front storage tank of the boron recovery system for pressurizer gas phase scavenging) purge pipeline was put into operation for hydrogen purging;

[0129] (3) The expected control range of dissolved hydrogen in the main circuit is 25-35ml / kg;

[0130] If ≤26ml / kg, stop purging (the main control room closes REN121 / 131VP (the nuclear island on the nuclear sampling system purge pipeline (RCP011LG) is bounded by the containment shell and the inner and outer isolation valves, REN121VP is inside the island, REN131VP is outside the island)), and when it rises to 28ml / kg, continue purging (the main control room notifies the chemical personnel to resume).

[0131] (4) The RCP010 test (a test for calculating the primary circuit leakage rate) during the PZR (reactor cooler system pressurizer) purge period is scheduled to be performed at around 4:00 a.m. every day to ensure the duration of the night purge. When the RCP010 test is performed, the main control room directly shuts down the REN121 / 131VP, and the chemical personnel re-operate the purge pipeline after work in the morning;

[0132] (5) To improve the accuracy of hydrogen meter measurement, the instrument control personnel shall cancel the automatic regeneration function of the hydrogen meter when starting the scavenging process, and the function shall not be restored until the chemical platform (120 degrees, 25 bar) is started. The chemical personnel shall provide the instrument control personnel with a ticket in advance;

[0133] (6) During the scavenging period, the on-duty personnel do not perform manual regeneration of the hydrogen meter. The chemistry department shall increase the frequency of manual analysis of dissolved hydrogen according to the needs or require the on-duty personnel of the operation department to manually regenerate the hydrogen meter;

[0134] (7) Conduct sampling analysis of R plant and ETY emission application.

[0135] Step 4: Preparation 72h to 48h before subcriticality:

[0136] (1) Continue to scavenge air through PZR-TEP001BA;

[0137] (2) The expected control range of dissolved hydrogen in the main circuit is 25-35ml / kg;

[0138] If ≤26ml / kg, stop scavenging (the main control room shuts down REN121 / 131VP), and when it rises back to 28ml / kg, continue scavenging (the main control room notifies the chemical personnel to resume).

[0139] (3) During the PZR scavenging period, the RCP010 test is scheduled to be performed at around 4:00 a.m. every day to ensure the duration of nighttime scavenging. When performing the RCP010 test, the main control room directly shuts down REN121 / 131VP and re-commissions the scavenging pipeline.

[0140] Step 5: 48 hours to 24 hours before subcriticality:

[0141] (1) Continue to scavenge air through PZR-TEP001BA;

[0142] The expected control range of dissolved hydrogen in the main circuit is 22-30ml / kg;

[0143] If it is ≤26ml / kg, stop scavenging (the main control room shuts down REN121 / 131VP); if it rises back to 28ml / kg, continue scavenging (the main control room notifies the chemical personnel to resume).

[0144] Step 6: 24 hours before subcriticality:

[0145] (1) 24 hours before subcriticality, RCV002BA was changed to nitrogen blanketing;

[0146] Purge RCV002BA with nitrogen (recommendations are given depending on hydrogen concentration and radioactive gas levels);

[0147] From subcritical to 120°C, keep RCV001DE (chemical and volume control system desalination bed (mixed bed, used to purify primary circuit water quality)) running, and add lithium according to the activity of I-131 (add lithium each time according to the upper limit of the expected value of the boron-lithium coordination diagram) to improve the iodine removal efficiency;

[0148] Scavenging by PZR-TEP001BA;

[0149] The expected control range of dissolved hydrogen is 9-25ml / kg, and the optimal range is 9-11ml / kg;

[0150] If it is ≤9ml / kg, stop scavenging (the main control room shuts down REN121 / 131VP), and if it rises back to 10ml / kg, continue scavenging (the main control room notifies the chemical personnel to resume on-site operation);

[0151] Xenon-iodine control target before load reduction (expected value):

[0152] Xe-133<8000MBq / t;

[0153] I-131<2000MBq / t.

[0154] When the xenon-iodine control target before load reduction is met, chemical control during the overhaul downtime is performed. Figure 2 The specific steps shown are as follows:

[0155] Step 1: 1 hour before subcriticality:

[0156] (1) Scavenging by PZR-TEP001BA;

[0157] The expected control range of dissolved hydrogen is 5-20ml / kg, and the optimal range is 5-11ml / kg;

[0158] If it is ≤6ml / kg, stop scavenging (the main control room shuts down REN121 / 131VP), and if it rises back to 7ml / kg, continue scavenging (the main control room notifies the chemical personnel to resume on-site operation);

[0159] (2) RCV002BA nitrogen purge;

[0160] Perform nitrogen breathing purge on RCV002BA (raise the liquid level to 1.9m, then lower it to 1.3m, this practice is conducive to minimizing waste gas), at least 3 times per shift, until TEP002DZ (a degassing device of the boron recovery system, used to remove hydrogen, nitrogen and radioactive gases from the waste liquid of the reactor cooler system, also used for primary circuit degassing during overhaul, TEP system has two degassing devices, one is 001DZ and the other is 002DZ) is started;

[0161] Step 2: Post-subcritical - thermal shutdown platform:

[0162] (1) Start TEP002DZ as soon as possible to degas the main circuit after entering hot shutdown. Before degassing, notify the radiation protection personnel to isolate the relevant rooms, and the chemist will evaluate the impact of the remaining low-boron water in TEP008BA on the boron concentration of the primary circuit (after the degasser is incorporated, the boron concentration of the primary circuit cannot return to below the boron concentration of the cold shutdown);

[0163] (2) Continuous scavenging by PZR-TEP001BA;

[0164] The desired control range of dissolved hydrogen is <3ml / kg;

[0165] (3) RCV002BA nitrogen purge;

[0166] If TEP002DZ has been running continuously, it is not necessary to perform nitrogen purge on the head tank. Otherwise, perform nitrogen breathing purge on RCV002BA (raise the liquid level to 1.9m, then lower it to 1.3m. This method is conducive to minimizing exhaust gas to the greatest extent), at least 3 times per shift;

[0167] After the unit enters hot shutdown, samples are taken for analysis of RCP lithium and gamma spectra. If I-131>500MBq / t, lithium is added to the RCP, with the target value being the upper limit of the expected value of the boron-lithium coordination diagram;

[0168] Overall strategy: The plan is to add lithium hydroxide to the primary circuit to maximize the iodine purification efficiency and slow down the deposition of iodine; when the total waiting time is constant, extend the waiting time on the hot stop platform. At this time, the purification flow is large and the primary circuit is alkaline, which is conducive to the removal of iodine; because the start-up of the degasifier will consume a large amount of lithium, which is not conducive to iodine removal, it is recommended to appropriately postpone the start-up of TEP002DZ.

[0169] Step 3: Hot Stop Platform - RRA Connection:

[0170] (1) Continuous scavenging through PZR-TEP001BA;

[0171] The desired control range of dissolved hydrogen is <3ml / kg;

[0172] After the main circuit pressure drops to 40 bar, adjust REN201VP to fully open to ensure maximum flow rate scavenging;

[0173] Keep TEP002DZ to degas the main circuit;

[0174] (2) RCV002BA nitrogen purge;

[0175] If TEP002DZ has been running continuously, it is not necessary to perform nitrogen purge on the head tank. Otherwise, the operator shall perform nitrogen breathing purge on RCV002BA (lift the liquid level to 1.9m, then lower it to 1.3m. This method is conducive to minimizing exhaust gas to the greatest extent), at least 3 times per shift;

[0176] Xenon-iodine control target before RRA connection (expected value):

[0177] Xe-133<4000MBq / t;

[0178] I-131<2000MBq / t;

[0179] (3) Check the EBA (containment ventilation system) operation conditions, and put EBA into operation after the conditions are met; the EBA operation conditions are determined by referring to the most recent ETY sampling and analysis results of the containment before shutdown, and the KRT009MA is used as the standard. If it is less than 4.0MBq / m3, EBA can be started; otherwise, it cannot be started.

[0180] (4) During the RRA heating stage, flush TEP006DE with at least 5m3 of water (flush to the TEP header tank; flushing before commissioning at 120°C may cause the hydrogen and radioactive gases in the TEP header tank that has been purged to rise);

[0181] Radioactive control objectives (vapor cavity flooding conditions, limits):

[0182] Xe-133<4000MBq / t; I-131<2000MBq / t.

[0183] Step 4: During the steam cavity flooding process:

[0184] (1) Before flooding the steam chamber, shut down TEP002DZ when xenon and iodine meet the steam chamber extinguishing conditions. After hydrogen and oxygen separation is completed, if the radioactive gas rebounds significantly, strengthen the RCV002BA purge and it is recommended to put TEP002DZ into operation again; the steam chamber extinguishing conditions are: the radioactivity analysis results of the first loop are as follows: Xe-133 <4000MBq / t; I-131 <2000MBq / t.

[0185] (2) During the steam extinguishing process, PZR-TEP001BA is maintained for continuous scavenging, and the expected RCP dissolved hydrogen value after the steam extinguishing is <3ml / Kg;

[0186] (3) Carry out the steam chamber extinguishing according to the plan, raise the PZR water level in advance to the maximum extent possible while ensuring safety, and make sure to use the planned time for the steam chamber extinguishing to the maximum extent possible to control the amplitude of radioactive gas anti-dissolution and hydrogen rebound (the steam chamber is submerged to complete the RCP007 / 008 / 011MN liquid level of about 3.8m);

[0187] (4) Chemical personnel are on site during the flooding of the steam chamber, and pipeline tripping must be restored immediately;

[0188] (5) RCV002BA nitrogen purge;

[0189] (6) RCV002BA is continuously purged with nitrogen during the steam extinguishing process.

[0190] (7) After the steam cavity is flooded, keep the PZR-TEP001BA scavenging pipeline flowing for half an hour before stopping the scavenging pipeline;

[0191] (8) After the steam cavity is flooded, immediately analyze the RCP dissolved hydrogen and gamma ray. If the dissolved hydrogen rebound exceeds 3ml / Kg, notify the relevant professionals to prepare for chemical dehydrogenation. If the xenon-iodine rebound exceeds the rapid cooling condition, notify the mechanical personnel that the implementation of TSD RCV01 may need to be postponed;

[0192] (9) Rapid cooling and main circuit oxidation are allowed only when the radioactivity meets the following requirements (170℃→80℃ cooling control specifications, limits):

[0193] Xe-133<4000MBq / t; I-131<2000MBq / t.

[0194] Step 5: 170℃-80℃ (rapid cooling control):

[0195] (1) Cool down at the maximum rate; during the rapid cooling stage from 170℃ to 80℃, the temperature should be reduced at the maximum rate of 25℃ / h to avoid stopping:

[0196] No experiments that may affect the operation of the RRA pump are arranged during the rapid cooling stage;

[0197] Priority should be given to using RRA dual pump operation to cool down at the beginning of rapid cooling;

[0198] If the RRA is operated with a single pump, the RRA cooling flow rate should be maintained at the maximum value without exceeding the operating technical specifications and the RRA pump flow limit;

[0199] (2) When the temperature approaches 120℃, switch to TEP006DE (no need to flush at this time because it has been flushed in advance);

[0200] (3) RCV002BA nitrogen purge;

[0201] Perform nitrogen breathing purge on RCV002BA (raise the liquid level to 1.9m, then lower it to 1.3m, this method is conducive to minimizing waste gas), at least 3 times per shift, until 120℃;

[0202] (4) At 120℃, adjust the discharge flow to the minimum (about 6t / h), confirm that the desalination bed has been switched to TEP006DE, perform the last nitrogen purge of the control box, and the chemist analyzes the hydrogen content of the control box (required to be <2%, otherwise continue to purge until qualified);

[0203] (5) Shut down the online hydrogen meter at 90℃.

[0204] Step 6: 80℃-40℃ (two-stage cooling control):

[0205] (1) Perform dehydrogenation according to the chemical dehydrogenation plan (if chemical dehydrogenation may be performed after the steam chamber is extinguished, notify the mechanical personnel in advance and push TSD RCV01 (i.e. switch RCV002BA to connect to air, i.e. to air, which was previously connected to nitrogen) to chemical dehydrogenation before execution);

[0206] (2) Add 15 liters of hydrogen peroxide to the main circuit at 80 degrees;

[0207] (3) During the oxidation purification process, if the filter pressure difference exceeds the replacement limit or exceeds KRT010MA (that is, RCV002BA is switched to air, that is, to air, and before that it was connected to nitrogen) and exceeds the second-level alarm threshold, RCV001FI will not be isolated at this time. Specifically, based on the change trend of KRT monitoring data and the time from stopping the main pump, a comprehensive evaluation is made as to whether it needs to be replaced before stopping the main pump;

[0208] Dose rate change limit: relaxed from 6.5E-2 for KRT010MA to 1.45E-1Gy / h;

[0209] When the double-hole plate is put into operation, the filter replacement pressure difference is relaxed to 1.9 bar;

[0210] (4) If the RCV001FI needs to be replaced during the oxidation purification process, the replacement process should be started immediately:

[0211] During the filter isolation period, the desalination bed should be kept online normally;

[0212] Service personnel and operation personnel prepare work tickets and operation packages in advance, give priority to invoices for RCV001FI's isolated / online work, and arrange for experienced personnel to respond quickly;

[0213] The isolation and emptying of RCV001FI shall be carried out by skilled personnel;

[0214] Service personnel prepare in advance a plan for filter element replacement in case RCV001FI cannot be completely isolated;

[0215] After receiving the RCV001FI replacement notice from the operator, the time for the service personnel to arrive at the site for filter replacement should be less than 30 minutes during the day and less than 1 hour at night;

[0216] The filter element replacement process of the service personnel should be controlled within 2 hours from ticket collection to ticket return, and the isolation / online operation of the operating personnel should be controlled within 3 hours.

[0217] After the replacement is completed, the operator will put the filter into operation as soon as possible, and perform key path control during the replacement process. During the operation, attention should be paid to the changes in the KRT036 / 016 / 017 / 020 / 021MA readings of the dual units to avoid triggering KRT over-threshold alarms;

[0218] Overhaul target: The total time from isolation to replacement and returning RCV001FI back online is less than 5 hours.

[0219] (5) After the oxygen concentration in the main circuit reaches 1 mg / Kg, notify the operator to adjust the downstream flow rate to the maximum of 27 t / h as soon as possible and purge Y2RCV002BA with air;

[0220] Radioactivity control (conditions for the last main pump to stop operating):

[0221] Xe-133<1500MBq / t; I-131<100MBq / t; Ag-110m<4000MBq / t; Co-58<25000MBq / t; total γ<50000MBq / t.

[0222] (6) The purification time before shutting down the main pump for overhaul shall be planned as 36 hours.

[0223] Step 7: 25bar-Manhole opening for the regulator:

[0224] (1)TEP006DE continuous purification;

[0225] (2) Except for the suspension of RCV002BA air purge during the depressurization process (to prevent the rapid rebound of radioactive gas and cause KRT alarm), the air purge should be maintained continuously at other times;

[0226] (3) After the pressure is reduced to 1.2 bar and stabilized for 6 hours, if I-131 is released but no peak is seen (it is still rising), the plan should be followed to perform a secondary pressure increase and decrease operation (secondary pressure increase to 25 bar without starting the main pump);

[0227] (4) After the pressure is reduced to 1.2 bar and stabilized for 6 hours, if I-131 has a peak value, but its decline rate is significantly lower than the theoretical purification rate, it indicates that there is a continuous release from the cladding. The plan should be implemented to perform a secondary pressure increase and decrease operation (secondary pressure increase to 25 bar, without starting the main pump);

[0228] (5) After the pressure is reduced to 1.2 bar and stabilized for 6 hours, if I-131 reaches a peak and its decline rate is greater than or equal to the theoretical purification rate, the plan for the secondary pressure increase and decrease operation will not be implemented.

[0229] (6) According to the source control plan, the radioactivity control limit before opening the pressurizer manhole for overhaul (case 1, if the main circuit is “fully opened” for the first time: opening the pressurizer manhole at a high liquid level of 0 m to 3.8 m; case 2, after the pressurizer manhole is opened: opening the reactor pressure vessel top cover or removing the core thermocouple):

[0230] Xe-133<1500MBq / t; I-131<100MBq / t.

[0231] Step 8: Open the manhole of the voltage stabilizer - open the large cover:

[0232] (1)TEP006DE continuous purification;

[0233] (2) RCV002BA maintains continuous purge;

[0234] (3) Before opening the cover, evacuate the RCP640VP;

[0235] (4) Radioactivity control limits under conditions of opening the main cover and filling the reactor pool:

[0236] Xe-133<1000MBq / t; I-131<100MBq / t; Co-58<2000MBq / t, expected value<1000MBq / t; total γ<4000MBq / t.

[0237] (5) After unloading and before loading, PTR001BA cycle purification (analysis after unloading, PTR tank purification after unloading should be arranged as soon as possible before loading, avoiding spent pool fuel operation) and chemical sampling for full analysis.

[0238] refer to Figure 3 , Figure 3 It is the downlink chemical control logic for the damaged neutron source unit.

[0239] Specifically, Figure 3 As shown, if the damage type of the core component is neutron source damage, the pre-overhaul preparation for the neutron source damaged unit includes: preparation 2 months before the overhaul; preparation 15 to 7 days before subcriticality; preparation 7 days to 24 hours before subcriticality; preparation 24 hours before criticality; judging whether the xenon-iodine control target before load reduction is met, if so, completing the pre-overhaul preparation for the fuel damaged unit; if the xenon-iodine control target before load reduction is not met, continuing to perform the preparation 24 hours before criticality.

[0240] In an embodiment of the present invention, the preparations for 2 months before the overhaul include: confirming that the efficiency of the desalting bed is normal, the filter aperture is 0.45 mm, and there are sufficient spare parts. The preparations for 15 to 7 days before subcriticality include: verifying the purification of the refueling water tank and the commissioning of the scavenging pipeline. Verify that the second orifice plate of the chemical and volumetric control system has been put into operation. Sampling and analyzing the air in the nuclear reactor building. The preparations for 7 days to 24 hours before subcriticality include: controlling the hydrogen purge of the control box; connecting the gas phase of the pressurizer of the reactor cooler system to the front storage tank of the boron recovery system to perform the gas phase purge of the pressurizer; and executing the emission application of the atmosphere monitoring system in the containment. The preparations for 24 hours before criticality include: continuing to purge the pressurizer gas phase by connecting the gas phase of the pressurizer of the reactor cooler system to the front storage tank of the boron recovery system; switching the chemical and volumetric control system control box to nitrogen coverage; and performing lithium addition control based on the activity of I-131.

[0241] Specifically, Figure 3 As shown, the chemical control during the downtime of the overhaul of the damaged neutron source unit includes: executing the control for 1 hour before subcriticality; executing the hot shutdown platform control after subcriticality; executing the connection of the residual heat removal system after the hot shutdown platform, and judging whether the xenon-iodine control target before the connection of the residual heat removal system, the steam cavity flooding radioactivity control target and the containment ventilation system commissioning conditions are met; if they are met, the steam cavity flooding is executed, and after the steam cavity flooding is completed, it is judged whether the rapid cooling control specification is met; if the rapid cooling control specification is met, rapid cooling is executed; if the main pump shutdown condition is met, the main pump shutdown is executed; if the radioactivity operation control condition is met, the 25bar-regulator manhole is opened; it is judged whether the radioactivity control value of the opening of the main cover and the reactor pool filling condition is met; if the radioactivity control value of the opening of the main cover and the reactor pool filling condition is met, the unloading is started.

[0242] Among them, the xenon-iodine control target before the connection of the residual heat removal system is: Xe-133<4000MBq / t, I-131<2000MBq / t; the steam cavity flooding radioactivity control target is: Xe-133<4000MBq / t, I-131<2000MBq / t; the containment ventilation system commissioning conditions are: I-131eq<4400MBq / t, KRT009MA<4.0MBq / m 3; Rapid cooling control specifications are: Xe-133<4000MBq / t, I-131<2000MBq / t; Main pump shutdown control conditions include: first operation control conditions and second operation control conditions; The first operation control condition is: γt<50000MBq / t, Xe-133<15000MBq / t, I-131<100MBq / t, Ag-110m<4000MBq / t, Co-58<25000MBq / t, Sb-124<4000MBq / t; The second operation control condition is: γt<50000MBq / t, Xe-133<15 000MBq / t, I-131<100MBq / t, Ag-110m<4000MBq / t, Co-58+Sb-124<25000MBq / t, Sb-124<4000MBq / t; the opening conditions are: Xe-133<1500MBq / t, I-131<100MBq / t; the radioactivity control values ​​of opening the large cover and reactor pool filling conditions are: Xe-133<1000MBq / t, I-131<50MBq / t, Co-58<2000MBq / t, expected value<1000MBq / t, total γ<4000MBq / t.

[0243] like Figure 3 As shown in FIG. 1 , the chemical control of the downlink of the neutron source damaged unit specifically includes the following steps:

[0244] Step 1: Preparation 2 months before overhaul:

[0245] Verify the efficiency of the desalination bed and determine whether the resin needs to be replaced based on the efficiency. Specifically:

[0246] (3) Evaluate the efficiency of TEP007DE (primary-loop boron removal bed (anion bed)) to prepare for boron removal at the end of its life;

[0247] (4) Confirm that the desalination bed efficiencies of PTR001DE (spent fuel pool purification desalination bed (mixed bed)), TEP006DE (overhaul of primary circuit purification desalination bed (mixed bed)), TEP002 / 004DE (boron recovery system desalination bed (002DE is a cation bed, 004DE is a mixed bed)), and RCV001 / 002DE (chemical and volume control system desalination bed (mixed bed)) meet the overhaul requirements, otherwise make a replacement plan. Among them, the overhaul requirements are: the desalination bed is not invalid and the efficiency is above 90%.

[0248] Confirm that RCV001FI (chemical and volume control system desalination bed filter), PTR001FI (spent fuel pool filter), PTR003 / 004FI (reactor pool filter) are used in overhaul. 0.45μm pore size filter, and verify whether the number of filter spare parts and the number of replaced filter shielding containers are sufficient. Among them, whether the number of filter shielding containers is sufficient is based on actual application, generally 1 to 2, with sufficient installation as the standard.

[0249] Step 2: Subcritical 15 days to 7 days preparation:

[0250] (1) PTR001BA (refueling water tank) purification before overhaul:

[0251] Before the overhaul, PTR001BA was purified for 48 hours. During and after the purification process, samples were taken for analysis of turbidity, B (boron) turbidity (target value < 0.1 NTU) and γt (total radioactivity) (target value < 10 MBq / t);

[0252] (2) Verify the scavenging pipeline:

[0253] The overhaul plan is included in the plan in advance and verified 15 days before subcriticality;

[0254] 15 days before subcriticality, adjust REN201VP (the isolating valve before the primary heat exchanger on the purge air pipeline of the nuclear sampling system) to a quarter of the opening (generally: first completely close, then idle during the opening process, and rotate a quarter of a turn after the valve is stressed. A major overhaul found that the opening of REN201VP needs to be adjusted several times each time the pipeline is put back into operation), and restore its opening when the primary circuit is depressurized to 40 bar; before opening the purge air pipeline, notify the radiation protection professionals to isolate the relevant rooms and pay attention to the KRT value (specifically: pay attention to whether the KRT reading rises, etc., whether it will exceed its alarm threshold (different KRTs have different alarm thresholds, that is, pay attention to the KRT of the room where the purge air pipeline passes, mainly to prevent pipeline leakage or other accidents), and put the purge air pipeline into operation for 1 hour for verification;

[0255] (3) Confirm the commissioning of the second RCV (chemical and volume control system) orifice plate;

[0256] (4) Fill the tank pool (spent fuel tank storage pool of the reactor water pool and the spent fuel pool cooling and treatment system (PTR)) with water to about 1.5 meters from the top of the pool. After circulation, chemical personnel take samples from the tank pool for boron and anion testing;

[0257] (5) 15 days before the overhaul, sample the RX air (the air in the nuclear reactor building) and evaluate whether the EVF (air purification system in the containment) needs to be put into operation (this sampling is done for CO measurement). According to the ETY sampling and analysis results, determine whether the ETY (atmospheric monitoring system in the containment) low-flow purge needs to be put into operation. Among them, the most recent ETY sampling and analysis results of the containment before the shutdown (iodine box I-131 activity concentration) shall prevail, and refer to the KRT008 / 009 / 028MA value before the EBA is put into operation for judgment. If I-131 is greater than the detection limit, it indicates iodine contamination and the EVF needs to be started; otherwise, there is no iodine contamination and the EVF does not need to be started.

[0258] The 7 days to 24 hours before subcriticality can be divided into three preparation stages: 7 days to 3 days before subcriticality, 72h to 48h before subcriticality, and 48h to 24h before subcriticality. The details are as follows:

[0259] Step 3: Preparation 7 to 3 days before subcriticality:

[0260] (1) 7 days before subcriticality, start the pre-operation of hydrogen purge of the control box. According to the hydrogen content of the primary circuit, arrange to adjust the hydrogen pressure of RCV002BA (chemical and volume control system control box) to 1.4 bar (empirical value);

[0261] (2) 7 days before the overhaul of subcriticality, the PZR-TEP001BA (referring to the down stage of overhaul, connecting the gas phase of the pressurizer of the reactor cooler system to the front storage tank of the boron recovery system for pressurizer gas phase scavenging) purge pipeline was put into operation for hydrogen purging;

[0262] (3) The expected control range of dissolved hydrogen in the main circuit is 25-35ml / kg;

[0263] If ≤26ml / kg, stop purging (the main control room closes REN121 / 131VP (the nuclear island on the nuclear sampling system purge pipeline (RCP011LG) is bounded by the containment shell and the inner and outer isolation valves, REN121VP is inside the island, REN131VP is outside the island)), and when it rises to 28ml / kg, continue purging (the main control room notifies the chemical personnel to resume).

[0264] (4) The RCP010 test (a test for calculating the primary circuit leakage rate) during the PZR (reactor cooler system pressurizer) purge period is scheduled to be performed at around 4:00 a.m. every day to ensure the duration of the night purge. When the RCP010 test is performed, the main control room directly shuts down the REN121 / 131VP, and the chemical personnel re-operate the purge pipeline after work in the morning;

[0265] (5) To improve the accuracy of hydrogen meter measurement, the instrument control personnel shall cancel the automatic regeneration function of the hydrogen meter when starting the scavenging process, and the function shall not be restored until the chemical platform (120 degrees, 25 bar) is started. The chemical personnel shall provide the instrument control personnel with a ticket in advance;

[0266] (6) During the scavenging period, the on-duty personnel shall not perform manual regeneration of the hydrogen meter. The chemistry department shall increase the frequency of manual analysis of dissolved hydrogen according to the needs or require the on-duty personnel of the operation department to manually regenerate the hydrogen meter;

[0267] (7) Conduct sampling analysis of R plant and ETY emission application.

[0268] Step 4: Preparation 72h to 48h before subcriticality:

[0269] (1) Continue to scavenge air through PZR-TEP001BA;

[0270] (2) The expected control range of dissolved hydrogen in the main circuit is 25-35ml / kg;

[0271] If ≤26ml / kg, stop scavenging (the main control room shuts down REN121 / 131VP), and when it rises back to 28ml / kg, continue scavenging (the main control room notifies the chemical personnel to resume).

[0272] (3) During the PZR scavenging period, the RCP010 test is scheduled to be performed at around 4:00 a.m. every day to ensure the duration of nighttime scavenging. When performing the RCP010 test, the main control room directly shuts down REN121 / 131VP and re-commissions the scavenging pipeline.

[0273] Step 5: 48 hours to 24 hours before subcriticality:

[0274] (1) Continue to scavenge air through PZR-TEP001BA;

[0275] The expected control range of dissolved hydrogen in the main circuit is 22-30ml / kg;

[0276] If it is ≤26ml / kg, stop scavenging (the main control room shuts down REN121 / 131VP); if it rises back to 28ml / kg, continue scavenging (the main control room notifies the chemical personnel to resume).

[0277] Step 6: 24 hours before subcriticality:

[0278] (1) 24 hours before subcriticality, RCV002BA was changed to nitrogen blanketing;

[0279] Purge RCV002BA with nitrogen (recommendations are given depending on hydrogen concentration and radioactive gas levels);

[0280] From subcritical to 120°C, keep RCV001DE (chemical and volume control system desalination bed (mixed bed, used to purify primary circuit water quality)) running, and add lithium according to the activity of I-131 (add lithium each time according to the upper limit of the expected value of the boron-lithium coordination diagram) to improve the iodine removal efficiency;

[0281] Scavenging by PZR-TEP001BA;

[0282] The expected control range of dissolved hydrogen is 9-25ml / kg, and the optimal range is 9-11ml / kg;

[0283] If it is ≤9ml / kg, stop scavenging (the main control room shuts down REN121 / 131VP), and if it rises back to 10ml / kg, continue scavenging (the main control room notifies the chemical personnel to resume on-site operation);

[0284] Xenon-iodine control target before load reduction (expected value):

[0285] Xe-133<8000MBq / t;

[0286] I-131<2000MBq / t.

[0287] When the xenon-iodine control target before load reduction is met, chemical control during the overhaul downtime is performed. Figure 3 The specific steps shown are as follows:

[0288] Step 1: 1 hour before subcriticality:

[0289] (1) Scavenging by PZR-TEP008BA;

[0290] The expected control range of dissolved hydrogen is 5-20ml / kg, and the optimal range is 5-11ml / kg;

[0291] If ≤6ml / kg, stop scavenging (the main control room shuts down REN121 / 131VP); if it rises back to 7ml / kg, continue scavenging (the main control room notifies the chemical personnel to resume);

[0292] (2) RCV002BA nitrogen purge;

[0293] If necessary, purge RCV002BA with nitrogen.

[0294] Step 2: Post-subcritical - thermal shutdown platform:

[0295] (1) Continuous scavenging is performed through PZR-TEP008BA (a front storage tank for the boron recovery system. Generally, the TEP system has two front storage tanks, the other of which is TEP001BA, which receives wastewater from different units respectively);

[0296] The expected control range of dissolved hydrogen is <5ml / kg;

[0297] (2) RCV002BA nitrogen purge;

[0298] Strengthen the nitrogen purge of RCV002BA to achieve the target concentration;

[0299] (3) When necessary, TEP001DZ performs degassing of the main circuit;

[0300] (4) Radioactive control objectives (steam cavity flooding conditions):

[0301] Xe-133<4000MBq / t; I-131<2000MBq / t.

[0302] (5) TEP006DE is put into operation after the unit enters hot shutdown.

[0303] Step 3: Hot Stop Platform - RRA Connection:

[0304] (1) During the process from hot shutdown to RRA connection, if KRT001 / 026MA triggers the secondary threshold alarm at the same time, the unit is controlled according to SOP. To avoid the above situation, the following control strategies are adopted:

[0305] When KRT001MA triggers the first-level alarm and KRT026MA reaches 1 / 2 of the second-level alarm, the pressure reduction should be stopped.

[0306] When KRT001MA triggers the second level alarm, the pressure reduction should be stopped.

[0307] (2) At this pressure platform, maintain maximum flow purification of one circuit.

[0308] (3) Put TEP006DE into operation for purification;

[0309] (4) Continuous scavenging by PZR-TEP008BA;

[0310] The expected control range of dissolved hydrogen is <5ml / kg;

[0311] After the main circuit pressure drops to 40 bar, the operator adjusts REN201VP to fully open to ensure maximum flow rate scavenging;

[0312] (5) RCV002BA nitrogen purge;

[0313] Strengthen the nitrogen purge of RCV002BA to achieve the target concentration;

[0314] (6) (When necessary) TEP001DZ performs degassing of the main circuit;

[0315] Radioactive control objectives:

[0316] Xe-133<4000MBq / t; I-131<2000MBq / t.

[0317] EBA operation conditions are met and EBA is put into operation; among them, EBA operation conditions are:

[0318] I-131eq<4400MBq / t;KRT009MA<4.0MBq / m 3 .

[0319] Step 4: During the steam cavity flooding process:

[0320] (1) During the steam extinguishing process, PZR-TEP008BA is maintained for continuous scavenging, and the expected RCP dissolved hydrogen value after the steam extinguishing is <3ml / Kg;

[0321] Extinguish the steam chamber as planned, raise the PZR water level in advance to the maximum extent possible while ensuring safety, and make sure to use up the planned time for the steam chamber (this time, 2 hours is planned in addition to the time for raising the water level in advance) to control the hydrogen rebound amplitude to the maximum extent possible;

[0322] During the flooding of the steam cavity, chemical personnel will be on site to provide protection, and any pipeline tripping must be put into operation immediately;

[0323] TEP001DZ stops operating before flooding the air cavity (if necessary);

[0324] (2) RCV002BA nitrogen purge;

[0325] The operator purged the RCV002BA with nitrogen to achieve the target concentration;

[0326] (3) After the steam cavity is flooded, immediately analyze the RCP dissolved hydrogen. If the dissolved hydrogen rebound exceeds 3ml / Kg, follow the "Overhaul Chemical Hydrogen Removal Plan";

[0327] Radioactive control target (cooling control specification): Xe-133<4000MBq / t; I-131<2000MBq / t.

[0328] Step 5: 177℃-80℃ (rapid cooling control):

[0329] (1) Cool down at the maximum rate; control the cooling rate at 25-28℃ / h; as long as there is a temperature margin, reduce the pressure to the target pressure platform as soon as possible to carry out the work of the pressure platform (pressure reduction rate <4bar / min); at each pressure platform, if there is no special requirement, maintain the original cooling rate; reduce the residence time at the intermediate low pressure platform;

[0330] (2) RCV002BA nitrogen purge;

[0331] RCV002BA performs nitrogen purge to 120℃. After the last nitrogen purge, the chemist analyzes the hydrogen content (required to be <2%, otherwise continue to purge until qualified);

[0332] When the temperature is about 120℃, adjust the discharge flow rate to the minimum (about 6t / h), perform the last nitrogen purge of the control box, and analyze the hydrogen content of the control box (required to be <2%, otherwise continue to purge until qualified);

[0333] The online hydrogen meter will be shut down at 100°C;

[0334] Radioactivity and gas control limits (temperature control specification 177℃→80℃): Xe-133<4000MBq / t; I-131<2000MBq / t.

[0335]

[0336] (3) In NS / RRA mode, after hydrogen peroxide is added to the primary circuit, the radioactivity will reach a peak. As a countermeasure, according to routine practice, the first and second alarm thresholds of KRT026MA need to be adjusted:

[0337] KRT026MA Before adjustment After adjustment Level 1 alarm threshold 2.5×10-4Gy / h 1×10-3Gy / h Second level alarm threshold 2×10-3Gy / h 2×10-2Gy / h

[0338] (4) When conditions are met, the first and second level alarm thresholds of KRT026MA should be adjusted as soon as possible.

[0339] (5) After adjusting this threshold, the threshold for KRT026MA to trigger the second-level alarm is greatly reduced, but it does not rule out that KRT026MA will trigger the second-level alarm when the oxidation peak occurs. If the KRT001 / 026MA second-level threshold alarm occurs, the control strategy is as follows:

[0340] Close the charging, reduce the shaft seal injection flow, and control the primary circuit pressure to not exceed the RRA safety valve set value by cooling;

[0341] Suspend RCP001 / 002 / 003PO;

[0342] Execute the DOSR procedure as quickly as possible, and execute according to the alarm card after the SOP procedure (state-oriented accident handling procedure) is issued;

[0343] Notify the instrument control personnel to enforce RPE003KG;

[0344] The sampling circuit is put into operation, and sampling and analysis of the primary circuit can be carried out;

[0345] Put the upper charging and lower discharging purification circuit into operation and restore the shaft seal return water and other operating equipment;

[0346] Restart the main pump to restore primary circuit purification;

[0347] Wait for the KRT001 / 026MA level 2 alarm to recover.

[0348] Among them, KRT036 / 016 / 017 / 020 / 021 / 001MA are all instruments used to monitor radioactivity in the KRT system of the power plant radiation monitoring system. Among them, KRT001MA monitors the radioactivity of the liquid in the RCV002BA, i.e. the chemical and volume control system volume control box, and KRT026MA monitors the radioactivity in the glove box (a cabinet box used for centralized sampling) area of ​​the nuclear sampling system room of the REN system.

[0349] Step 6: 80℃-40℃ (two-stage cooling control):

[0350] (1) Before the first-loop oxidation, the pore size of the RCV001FI filter element is maintained at 0.1 μm;

[0351] (2) Add 15 liters of hydrogen peroxide to the main circuit at 80°C;

[0352] (3) After the oxygen concentration in the main circuit reaches 1 mg / Kg, notify the operator to purge RCV002BA with air and adjust the downstream flow rate to a maximum of 27 t / h as soon as possible;

[0353] Radioactivity control (conditions for the last main pump to stop operating):

[0354] Condition 1:

[0355] γt<50000MBq / t; Xe-133<1500MBq / t; I-131<100MBq / t; Co-58<25000MBq / t; Ag-110m<4000MBq / t; Sb-124<4000MBq / t (expected value);

[0356] This condition applies to oxidation purification within 28 hours after the main pump shutdown conditions are met. It is recommended to continue to use the 28-hour purification time standard.

[0357] Condition 2:

[0358] γt<50000MBq / t; Xe-133<1500MBq / t; I-131<100MBq / t; Ag-110m<4000MBq / t; Co-58+Sb-124<25000MBq / t; Sb-124<4000MBq / t (expected value);

[0359] This condition applies to the criteria that all gamma spectroscopy analysis items must meet when the oxidation purification time reaches 28 hours.

[0360] Step 7: 25bar-Manhole opening for the regulator:

[0361] (1)TEP006DE continuous purification;

[0362] Radioactivity control limit before opening the pressurizer manhole (case 1, if the main circuit is "fully opened" for the first time: open the pressurizer manhole at a high liquid level of 0 meters to 3.8 meters; case 2, after the pressurizer manhole is opened: open the reactor pressure vessel top cover or remove the core thermocouple):

[0363] Xe-133<1500MBq / t; I-131<100MBq / t.

[0364] Step 8: Open the manhole of the voltage stabilizer - open the large cover:

[0365] (1)TEP006DE continuous purification;

[0366] (2) Radioactivity control limit under open cover condition:

[0367] Xe-133<1000MBq / t; I-131<50MBq / t;

[0368] Reactor pool water filling condition radioactivity control limit:

[0369] Co-58<2000MBq / t; expected value<1000MBq / t; γt<4000MBq / t;

[0370] (2) After unloading and before loading, the PTR001BA cycle is purified as planned (the purification of the PTR tank is arranged to be carried out just before loading to avoid the operation of the spent water pool personnel), and sampling is fully analyzed.

[0371] After the above processing steps, the fuel damaged unit and the neutron source damaged unit did not have KRT accidental secondary alarm, no external exposure of personnel occurred, no radioactivity was released to the environment, and the critical path was not delayed due to radioactivity problems.

[0372] refer to Figure 4 , Figure 4 The present invention provides a principle block diagram of a chemical control system during the overhaul shutdown of a nuclear power plant unit when a core component is damaged.

[0373] Specifically, Figure 4 As shown, the chemical control system during the overhaul shutdown of the unit when the core components of the nuclear power plant are damaged includes:

[0374] A damage type determination unit 401 is used to determine the damage type of the core component;

[0375] The fuel damage chemical control unit 402 is used to perform pre-overhaul preparation of the fuel damage unit if the damage type of the core component is fuel damage, and after the pre-overhaul preparation is completed, perform chemical control during the overhaul downtime of the fuel damage unit;

[0376] The neutron source damage chemical control unit 403 is used to perform pre-overhaul preparations for the neutron source damaged unit if the core component damage type is neutron source damage, and after the pre-overhaul preparations are completed, perform chemical control during the overhaul downtime of the neutron source damaged unit.

[0377] Specifically, the specific coordination operation process between the various units in the chemical control system during the overhaul shutdown of the unit when the core components of the nuclear power plant are damaged can refer to the above-mentioned chemical control method during the overhaul shutdown of the unit when the core components of the nuclear power plant are damaged, and will not be repeated here.

[0378] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0379] Professionals may further appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in the above description according to function. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians may use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0380] The steps of the method or algorithm described in conjunction with the embodiments disclosed herein may be implemented directly using hardware, a software module executed by a processor, or a combination of the two. The software module may be placed in a random access memory (RAM), a memory, a read-only memory (ROM), an electrically programmable ROM, an electrically erasable programmable ROM, a register, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.

[0381] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot limit the scope of protection of the present invention. All equivalent changes and modifications made to the scope of the claims of the present invention should fall within the scope of the claims of the present invention.

Claims

1. A chemical control method during the overhaul shutdown of a nuclear power plant unit when a core component is damaged, characterized in that: The following steps are involved: Determining the damage type of the core component; the damage type of the core component includes: fuel damage or neutron source damage; If the damage type of the core component is fuel damage, pre-overhaul preparation for the fuel damaged unit is performed, and after the pre-overhaul preparation is completed, chemical control during the downtime of the fuel damaged unit overhaul is performed; If the damage type of the core component is neutron source damage, pre-overhaul preparation for the unit with damaged neutron source is performed, and after the pre-overhaul preparation is completed, chemical control during the overhaul downtime of the unit with damaged neutron source is performed.

2. The chemical control method for nuclear power plant unit overhaul shutdown when core components are damaged according to claim 1, characterized in that: If the damage type of the core component is fuel damage, performing the pre-overhaul preparation of the fuel damage unit includes: Preparation 2 months before the overhaul; Preparations 15 to 7 days before executing subcriticality; Preparation 7 days to 24 hours before executing subcriticality; Preparation 24 hours before execution of critical; Determine whether the xenon-iodine control target before load reduction is met. If so, complete the pre-overhaul preparation for the fuel-damaged unit; If the xenon-iodine control target before load reduction is not met, continue to perform the preparation for the 24 hours before criticality.

3. The chemical control method for nuclear power plant unit overhaul shutdown when core components are damaged according to claim 2, characterized in that: The preparations for the two months before the overhaul include: Make sure the desalination bed is efficient, the filter pore size is 0.45 mm, and there are enough spare parts; The preparations for the 15 to 7 days before the implementation of subcriticality include: Verify the purification of the refueling water tank and the commissioning of the scavenging pipeline; Confirm that the second downhole orifice of the chemical and volume control system has been put into operation; Sampling and analyzing the air in nuclear reactor buildings; The preparations 7 days to 24 hours before executing subcriticality include: Control volume and control box hydrogen purge; Connecting the gas phase of the pressurizer of the reactor cooler system to the front storage tank of the boron recovery system to perform pressurizer gas phase scavenging; Execute the discharge application of the atmosphere monitoring system in the containment; The preparations for the critical 24 hours before execution include: Continue to purge the pressurizer gas phase by connecting the gas phase of the reactor cooler system pressurizer to the front storage tank of the boron recovery system; Switch the chemical and volume control system tanks to nitrogen blanketing; Lithium addition control is based on I-131 activity.

4. The chemical control method for nuclear power plant unit overhaul shutdown when core components are damaged according to claim 1, characterized in that: If the damage type of the core component is neutron source damage, the pre-overhaul preparation for the neutron source damaged unit includes: Preparation 2 months before the overhaul; Preparations 15 to 7 days before executing subcriticality; Preparation 7 days to 24 hours before executing subcriticality; Preparation 24 hours before execution of critical; Determine whether the xenon-iodine control target before load reduction is met. If so, complete the pre-overhaul preparation for the damaged neutron source unit; If the xenon-iodine control target before load reduction is not met, continue to perform the preparation for the 24 hours before criticality.

5. The chemical control method for nuclear power plant unit overhaul shutdown when core components are damaged according to claim 4, characterized in that: The preparations for the two months before the overhaul include: Make sure the desalination bed is efficient, the filter pore size is 0.45 mm, and there are enough spare parts; The preparations for the 15 to 7 days before the implementation of subcriticality include: Verify the purification of the refueling water tank and the commissioning of the scavenging pipeline; Confirm that the second orifice plate of the chemical and volume control system is in operation; Sampling and analyzing the air in nuclear reactor buildings; The preparations 7 days to 24 hours before executing subcriticality include: Control volume and control box hydrogen purge; Connecting the gas phase of the pressurizer of the reactor cooler system to the front storage tank of the boron recovery system to perform pressurizer gas phase scavenging; Execute the discharge application of the atmosphere monitoring system in the containment; The preparations for the critical 24 hours before execution include: Continue to purge the pressurizer gas phase by connecting the gas phase of the reactor cooler system pressurizer to the front storage tank of the boron recovery system; Switch the chemical and volume control system tanks to nitrogen blanketing; Lithium addition control is based on I-131 activity.

6. The chemical control method for nuclear power plant unit overhaul shutdown when core components are damaged according to claim 1, characterized in that: The chemical control during the downtime of the overhaul of the fuel damaged unit includes: Execute control 1 hour before subcriticality; Execute post-subcritical hot stop platform control; Execute the connection of the residual heat removal system of the hot shutdown platform and determine whether the xenon-iodine control target and the steam cavity flooding radioactivity control target before the connection of the residual heat removal system are met; If it is satisfied, the steam cavity flooding is executed, and after the steam cavity flooding is completed, it is determined whether the rapid cooling control specification is met; If the rapid cooling control specification is met, rapid cooling is performed; If the main pump shutdown conditions are met, the main pump shutdown is executed; If the radioactive operation control conditions are met, the 25bar-pressure regulator manhole is opened; Determine whether the radioactivity control values ​​for opening the main cover and filling the reactor pool are met; If the radioactivity control values ​​for opening the main cover and filling the reactor pool with water are met, unloading is started.

7. The chemical control method for nuclear power plant unit overhaul shutdown when core components are damaged according to claim 6, characterized in that: The xenon-iodine control targets and radioactivity control targets before the waste heat removal system is connected include: The xenon-iodine control targets before the waste heat removal system is connected are: Xe-133<4000MBq / t, I-131<2000MBq / t; The steam cavity flooding radioactivity control targets are: Xe-133 <4000MBq / t, I-131 <2000MBq / t; The rapid cooling control specification is: Xe-133<4000MBq / t, I-131<2000MBq / t; The main pump shutdown control conditions are: Xe-133<4000MBq / t, I-131<100MBq / t, Ag-110m<4000MBq / t, Co-58<25000MBq / t, total γ <25000MBq / t; The opening conditions are: Xe-133<1500MBq / t, I-131<100MBq / t; The radioactivity control values ​​of the conditions for opening the large cover and filling the reactor pool with water are: Xe-133<4000MBq / t, I-131<100MBq / t, Co-58<2000MBq / t, expected value<4000MBq / t, and total γ<4000MBq / t.

8. The chemical control method for nuclear power plant unit overhaul shutdown when core components are damaged according to claim 1, characterized in that: The chemical control during the downtime of the overhaul of the damaged neutron source unit includes: Execute control 1 hour before subcriticality; Execute post-subcritical hot stop platform control; After executing the hot shutdown platform, the residual heat removal system is connected, and it is determined whether the xenon-iodine control target, steam cavity flooding radioactivity control target and containment ventilation system commissioning conditions before the residual heat removal system is connected are met; If it is satisfied, the steam cavity flooding is executed, and after the steam cavity flooding is completed, it is determined whether the rapid cooling control specification is met; If the rapid cooling control specification is met, rapid cooling is performed; If the main pump shutdown conditions are met, the main pump shutdown is executed; If the radioactive operation control conditions are met, the 25bar-pressure regulator manhole is opened; Determine whether the radioactivity control values ​​for opening the main cover and filling the reactor pool are met; If the radioactivity control values ​​for opening the main cover and filling the reactor pool with water are met, unloading is started.

9. The chemical control method for nuclear power plant unit overhaul shutdown when core components are damaged according to claim 8, characterized in that: The xenon-iodine control targets before the waste heat removal system is connected are: Xe-133<4000MBq / t, I-131<2000MBq / t; The steam cavity flooding radioactivity control targets are: Xe-133 <4000MBq / t, I-131 <2000MBq / t; The operation conditions of the containment ventilation system are: I-131eq < 4400MBq / t, KRT009MA < 4.0MBq / m 3 ; The rapid cooling control specification is: Xe-133<4000MBq / t, I-131<2000MBq / t; The main pump shutdown control condition includes: a first operation control condition and a second operation control condition; The first operating control conditions are: γt<50000MBq / t, Xe-133<15000MBq / t, I-131<100MBq / t, Ag-110m<4000MBq / t, Co-58<25000MBq / t, Sb-124<4000MBq / t; The second operation control conditions are: γt<50000MBq / t, Xe-133<15000MBq / t, I-131<100MBq / t, Ag-110m<4000MBq / t, Co-58+Sb-124<25000MBq / t, Sb-124<4000MBq / t; The conditions after opening the hole are: Xe-133<1500MBq / t, I-131<100MBq / t; The radioactivity control values ​​under the conditions of opening the large cover and filling the reactor pool with water are: Xe-133<1000MBq / t, I-131<50MBq / t, Co-58<2000MBq / t, expected value<1000MBq / t, and total γ<4000MBq / t.

10. A chemical control system for a nuclear power plant unit during overhaul shutdown when a core component is damaged, characterized in that: include: A damage type determination unit, used to determine the damage type of the core component; The core component damage types include: fuel damage or neutron source damage; A fuel damage chemical control unit, for executing pre-overhaul preparations for the fuel-damaged unit if the damage type of the core component is fuel damage, and executing chemical control during the downtime of the overhaul of the fuel-damaged unit after the pre-overhaul preparations are completed; The neutron source damage chemical control unit is used to perform pre-overhaul preparation of the neutron source damaged unit if the damage type of the core component is neutron source damage, and after the pre-overhaul preparation is completed, perform chemical control during the overhaul downtime of the neutron source damaged unit.

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