A control method for boron content metering during overhaul of a nuclear power plant unit

Abstract

The present application belongs to control method, and particularly relates to a control method for boron table operation during overhaul of a nuclear power plant unit. The method comprises the following steps: step one, a pre-overhaul step; step two, a down-overhaul step; and step three, an up-overhaul step. The present application has the following remarkable effects: the present application comprehensively considers and formulates a defect rapid troubleshooting scheme when boron table operation is unsuccessful, which can effectively reduce the defect troubleshooting time when boron table operation is unsuccessful during overhaul, and save the overhaul period; secondly, after the defect troubleshooting positioning when boron table operation is unsuccessful, the present application formulates an effective boron table operation standby scheme according to different defects without increasing additional system facilities, ensures that the unit overhaul work continues normally, temporarily does not execute defect treatment, and then repairs and treats the positioned defects after the unit mode conversion, which can greatly reduce the time consumed for defect treatment when boron table operation is unsuccessful, further saves the overhaul period, and reduces economic losses.

Description

Technical Field

[0001] This invention pertains to control methods, specifically a control method for activating the boron meter in the primary loop during a major overhaul of a nuclear power plant unit. Background Technology

[0002] In existing pressurized water reactor nuclear power units, boron is typically added to the primary coolant to compensate for and control excess reactivity in the reactor core, flatten the core power distribution, increase burnup depth, and improve the economic efficiency and safety of the nuclear power unit operation. Additionally, boron is added during reactor shutdowns, refueling, or major overhauls to maintain the active zone in a subcritical state for extended periods. Therefore, boron-loaded nuclear power units employ a complete and independent online boron measurement system (referred to as a boron meter) to continuously monitor the boron concentration in the reactor and primary coolant. This prevents accidental dilution of boron in the reactor and primary coolant, which could lead to unexpected increases in reactor power and ensure safe unit operation.

[0003] The M310 pressurized water reactor unit operates in six modes throughout its service life: Reactor Power Operation (RP), Steam Generator Cooling Shutdown (NS / SG), Residual Heat Removal System Cooling Normal Shutdown (NS / RRA), Maintenance Shutdown (MCS), Refueling Shutdown (RCS), and Complete Discharge (RCD). The specific operating conditions of the primary circuit under each mode are described in the following table according to the operational specifications.

[0004]

[0005]

[0006] According to the unit operation technical specifications, except for the fully unloaded mode (RCD), the boron meter needs to be used in the other five operating modes to monitor the boron concentration in the primary coolant in real time to ensure unit safety. The table below shows whether the boron meter needs to be used in different operating modes and the measures to be taken when the boron meter is unavailable.

[0007]

[0008]

[0009] During major overhauls, the unit's operating mode is constantly changing, and the operating status of the primary loop's related systems, equipment, and pipelines also changes accordingly. To ensure that the boron meter can continuously monitor the boron concentration of the primary loop coolant, the sampling path for the boron meter's operation must also be switched synchronously. However, due to equipment defects, unsuccessful switching of the boron meter's sampling path frequently occurs, seriously affecting the safe operation of the unit and extending the overhaul period. For example, during an overhaul at a nuclear power plant, when the unit's operating mode was switched to NS / RRA and the sampling path for the boron meter's operation was being switched, the valve stem of the external isolation valve on the sampling pipeline broke, causing the boron meter to fail to operate successfully. This delayed the overhaul by approximately 9 hours, resulting in an estimated economic loss of approximately 2.7 million yuan.

[0010] Therefore, a control method is needed for the commissioning of the primary loop boron meter during the overhaul of a nuclear power plant unit. Summary of the Invention

[0011] This invention addresses the shortcomings of existing technologies by providing a control method for activating the primary loop boron meter during a major overhaul of a nuclear power plant unit.

[0012] This invention is implemented as follows: a control method for activating the primary loop boron meter during a major overhaul of a nuclear power plant unit, comprising the following steps:

[0013] Step 1: Pre-overhaul procedures;

[0014] Step Two: Downward Overhaul Procedures;

[0015] Step 3: Overhaul and upward movement steps.

[0016] The above-described control method for activating the primary loop boron meter during a nuclear power plant unit overhaul includes, wherein,

[0017] Step one includes,

[0018] (1) Before the overhaul begins - RP operation mode

[0019] Before the overhaul began, the unit was in reactor power operation mode (RP power operation). According to the operating technical specifications, the boron concentration of the primary coolant in this condition must meet the critical boron concentration. A boron meter was required to monitor the boron concentration of the primary coolant to ensure that the boron concentration of the primary coolant met the requirements. Under this condition, the three main pumps were in operation to circulate and cool the primary coolant, and the control box was in operation to return the purified primary coolant to the secondary loop. The waste heat discharge system's waste discharge pump was shut down, and the boron meter was in operation along the path of "secondary loop inlet water → boron meter → control box".

[0020] The above-described control method for activating the primary loop boron meter during a nuclear power plant unit overhaul includes, wherein,

[0021] Step two includes,

[0022] (2) Under the overhaul downlink NS / SG operating mode

[0023] After the overhaul begins, the primary coolant is cooled and depressurized, entering the steam generator cooling shutdown operation mode NS / SG. According to the operational technical specifications, the boron concentration of the primary coolant under this condition must meet the shutdown boron concentration requirement of ~2500ppm. A boron meter must be used to monitor the boron concentration of the primary coolant to ensure it meets the requirements. Under this condition, the three main pumps are in operation to circulate and cool the primary coolant, and the capacity control tank returns the purified primary coolant to the secondary loop. The waste heat removal system's waste heat pump is shut down, and the boron meter continues to operate along the path of "secondary loop inlet water → boron meter → capacity control tank".

[0024] (3) During the commissioning phase of the NS / RRA main pump during major overhaul, the operating mode is as follows:

[0025] The primary coolant continues to cool and depressurize, entering the residual heat removal system to cool the NS / RRA (Normal Shutdown / Remote Recirculation) system during normal shutdown. According to operational specifications, the boron concentration in the primary coolant under this condition must meet the shutdown boron concentration requirement of ~2500 ppm. A boron meter must be used to monitor the boron concentration in the primary coolant to ensure it meets the requirements. Under this condition, the three main pumps and the residual heat pump are in operation to circulate and cool the primary coolant. The capacity control tank returns the purified primary coolant to the secondary loop. The boron meter continues to operate along the path of "secondary loop inlet water → boron meter → capacity control tank."

[0026] (4) During the downlink NS / RRA-main pump shutdown phase of the overhaul, the operating mode is as follows:

[0027] The primary coolant continues to cool and depressurize. According to the operational technical specifications, the boron concentration of the primary coolant under this condition must meet the shutdown boron concentration requirement of ~2500ppm. A boron meter needs to be used to monitor the boron concentration of the primary coolant to ensure that the boron concentration of the primary coolant meets the requirements. Under this condition, the three main pumps and the capacity control box are shut down, and the waste heat pump is put into operation to circulate, cool, and purify the primary coolant. The boron meter operation path needs to be changed to "residual heat discharge system upstream water from the heat exchanger → boron meter → second loop".

[0028] (5) Under the overhaul downlink MCS operation mode

[0029] The primary coolant continues to cool and depressurize, entering the maintenance shutdown mode (MCS). According to the operational technical specifications, the boron concentration of the primary coolant under this condition must meet the requirement of 2300–2500 ppm. A boron meter must be used to monitor the boron concentration of the primary coolant to ensure it meets the requirements. Under this condition, the three main pumps and the capacity control tank are shut down. The waste heat pump is activated to circulate and purify the primary coolant. The boron meter continues to operate along the path of "waste heat discharge system upstream water from the heat exchanger → boron meter → second loop".

[0030] (6) Under the overhaul downlink RCS operation mode

[0031] The refueling water tank is filled to 15.5 meters, and the reactor enters the refueling shutdown mode (RCS). According to the operational technical specifications, the boron concentration of the primary coolant must meet the requirement of 2300-2500 ppm under this condition. A boron meter needs to be used to monitor the boron concentration of the primary coolant to ensure that the boron concentration of the primary coolant meets the requirements. Under this condition, the three main pumps and the capacity control box are shut down. The waste heat pump is put into operation to circulate and cool the primary coolant for purification. The boron meter continues to operate along the path of "waste heat discharge system upstream water of heat exchanger → boron meter → second loop".

[0032] (7) Under the overhaul downlink RCD operation mode

[0033] After the reactor unloading operation is completed, the reactor enters the full unloading mode (RCD). According to the operating technical specifications, there is no requirement for the boron concentration of the first loop coolant under this condition, and the boron meter does not need to be put into operation.

[0034] The above-described control method for activating the primary loop boron meter during a nuclear power plant unit overhaul includes, wherein,

[0035] Step (4) includes

[0036] After changing the boron meter's operation path to "water upstream of the waste heat discharge system heat exchanger → boron meter → second loop", check if the boron meter flow rate is greater than 50L / h.

[0037] If the boron meter flow rate does not meet the requirement of >50L / h, troubleshoot the defect according to the rapid troubleshooting plan for when the primary loop coolant boron meter commissioning path "waste heat discharge system upstream water of heat exchanger → boron meter → secondary loop" fails.

[0038] Based on the defects identified in the troubleshooting plan, the backup plan was selected: "waste heat discharge system upstream water from heat exchanger → boron meter → second loop". The boron meter was then put back into operation.

[0039] After restarting the boron meter, check if the flow rate of the boron meter is greater than 50L / h.

[0040] The above-described control method for activating the primary loop boron meter during a nuclear power plant unit overhaul includes, wherein,

[0041] Step three includes,

[0042] (8) Before overhauling the uplink RCS operation mode

[0043] After the unit completes its overhaul-related maintenance work in the reactor fully unloaded mode (RCD), the primary loop system and refueling pool are filled with water, and the residual heat removal system is activated to circulate and purify the primary loop coolant. Because the next step is for the unit to enter the refueling shutdown mode (RCS) for refueling operations, according to operational specifications, the boron concentration of the primary loop coolant in the RCS refueling shutdown mode must meet the requirement of 2300–2500 ppm. Therefore, a boron meter needs to be activated in advance to monitor the boron concentration of the primary loop coolant to ensure that it meets the 2300–2500 ppm requirement. At this time, the three main pumps and the capacity control box are shut down, and the residual heat removal pump is activated to circulate and purify the primary loop coolant. The boron meter activation path is: "upstream water from the heat exchanger of the residual heat removal system → boron meter → second loop".

[0044] (9) Overhaul uplink RCS operation mode

[0045] The unit enters the refueling shutdown mode (RCS) for refueling operations. According to the operational specifications, the boron concentration of the primary coolant must be between 2300 and 2500 ppm under this condition. A boron meter must be used to monitor the boron concentration of the primary coolant to ensure that it meets the requirements. Under this condition, the three main pumps and the capacity control box are shut down. The waste heat pump is used to circulate and cool the primary coolant for purification. The boron meter continues to operate along the path of "waste heat discharge system upstream water from the heat exchanger → boron meter → secondary loop".

[0046] (10) Overhaul uplink MCS operation mode

[0047] The primary coolant is gradually pressurized, entering the maintenance shutdown mode (MCS). According to the operational technical specifications, the boron concentration of the primary coolant under this condition must meet the requirement of 2300–2500 ppm. A boron meter needs to be used to monitor the boron concentration of the primary coolant to ensure that the boron concentration meets the requirements. Under this condition, the three main pumps and the capacity control box are shut down. The waste heat pump is put into operation to circulate and cool the primary coolant for purification. The boron meter continues to operate along the path of "waste heat discharge system upstream water from the heat exchanger → boron meter → second loop".

[0048] (11) During the overhaul and NS / RRA main pump shutdown phase, the operating mode is as follows:

[0049] The primary coolant continues to heat and pressurize, entering the residual heat removal system to cool the NS / RRA (Normal Shutdown / Remote Recirculation) system during normal shutdown. According to operational specifications, the boron concentration in the primary coolant under this condition must meet the shutdown boron concentration requirement of ~2500 ppm. A boron meter must be used to monitor the boron concentration in the primary coolant to ensure it meets the requirements. Under this condition, the three main pumps are shut down, and the residual heat removal pumps are activated to circulate and cool the primary coolant. The capacity control tank returns the purified primary coolant to the secondary loop. The boron meter continues to operate along the path of "upstream water from the heat exchanger in the residual heat removal system → boron meter → secondary loop".

[0050] (12) During the overhaul and commissioning of the NS / RRA main pump, the operating mode is as follows:

[0051] The primary coolant continues to heat and pressurize. Once the main pumps meet the commissioning conditions, they are put into operation. According to the operating technical specifications, the boron concentration of the primary coolant under this condition must meet the shutdown boron concentration requirement of ~2500ppm. A boron meter needs to be used to monitor the boron concentration of the primary coolant to ensure that it meets the requirements. Under this condition, the three main pumps and the residual discharge pump are in operation to circulate and cool the primary coolant. The capacity control box is in operation to return the purified primary coolant to the secondary loop. The boron meter operation path needs to be changed to "secondary loop inlet water → boron meter → capacity control box".

[0052] (13) Overhaul uplink NS / SG operation mode

[0053] The primary coolant continues to heat and pressurize, entering the steam generator cooling shutdown mode NS / SG. According to the operational technical specifications, the boron concentration of the primary coolant under this condition must meet the shutdown boron concentration requirement of ~2500ppm. A boron meter must be used to monitor the boron concentration of the primary coolant to ensure it meets the requirements. Under this condition, the three main pumps are in operation to circulate and cool the primary coolant. The capacity control box is in operation to return the purified primary coolant to the secondary loop. The waste heat removal system's waste discharge pumps are shut down. The boron meter continues to operate along the path of "secondary loop inlet water → boron meter → capacity control box".

[0054] (14) Overhauling Upward RP Operation Mode

[0055] The unit begins critical operation and enters reactor power operation mode (RP). According to the operating technical specifications, the boron concentration of the primary coolant must meet the critical boron concentration under this condition. A boron meter needs to be used to monitor the boron concentration of the primary coolant to ensure that the boron concentration of the primary coolant meets the requirements. Under this condition, the three main pumps are in operation to circulate and cool the primary coolant, and the capacity control box is in operation to return the purified primary coolant to the secondary loop. The waste heat removal system's waste discharge pump is in a stopped state, and the boron meter continues to operate along the path of "secondary loop inlet water → boron meter → capacity control box".

[0056] The above-described control method for activating the primary loop boron meter during a nuclear power plant unit overhaul includes, wherein,

[0057] Step (8) includes,

[0058] After changing the boron meter's operation path to "water upstream of the waste heat discharge system heat exchanger → boron meter → second loop", check if the boron meter flow rate is greater than 50L / h.

[0059] If the boron meter flow rate does not meet the requirement of >50L / h, troubleshoot the defect according to the rapid troubleshooting plan for when the primary loop coolant boron meter commissioning path "waste heat discharge system upstream water of heat exchanger → boron meter → secondary loop" fails.

[0060] Based on the defects identified in the troubleshooting plan, the backup plan was selected: "waste heat discharge system upstream water from heat exchanger → boron meter → second loop". The boron meter was then put back into operation.

[0061] After restarting the boron meter, check if the flow rate of the boron meter is greater than 50L / h.

[0062] The above-described control method for activating the primary loop boron meter during a nuclear power plant unit overhaul includes, wherein,

[0063] Step (12) includes,

[0064] After changing the boron meter's operation path to "second ring road water inlet → boron meter → capacity control box", check whether the boron meter flow rate is >50L / h.

[0065] If the boron meter flow rate does not meet the requirement of >50L / h, troubleshoot the defect according to the rapid troubleshooting plan for unsuccessful operation of the primary loop coolant boron meter via the "second loop inlet water → boron meter → capacity control box" route.

[0066] Based on the defects identified in the troubleshooting plan, the backup plan for the boron meter operation path of the primary coolant circuit was selected: "second loop water inlet → boron meter → capacity control box". The boron meter was then put back into operation.

[0067] After restarting the boron meter, check if the flow rate of the boron meter is greater than 50L / h.

[0068] The significant advantages of this invention are as follows: First, based on the design of sampling pipelines related to boron meter commissioning, this invention comprehensively considers and formulates a rapid defect investigation plan when boron meter commissioning fails. This can effectively reduce the defect investigation time during major overhauls when boron meter commissioning fails, thus saving overhaul time. Second, after locating the defect in boron meter commissioning failure, this invention formulates effective backup plans for boron meter commissioning according to different defects without adding additional system facilities. This ensures that the unit overhaul work can continue normally without performing defect handling. The defect will be repaired after the unit mode is switched, which can significantly reduce the time spent on defect handling when boron meter commissioning fails, further saving overhaul time and reducing economic losses. Detailed Implementation

[0069] A control method for activating the primary loop boron meter during a major overhaul of a nuclear power plant unit includes the following steps:

[0070] 1. Before the overhaul begins (RP operating mode)

[0071] Before the overhaul began, the unit was in reactor power operation mode (RP) power operation. According to the operating technical specifications, the boron concentration of the primary coolant in this condition must meet the critical boron concentration. A boron meter was required to monitor the boron concentration of the primary coolant to ensure that the boron concentration of the primary coolant met the requirements. Under this condition, the three main pumps were in operation to circulate and cool the primary coolant, the control box was in operation to return the purified primary coolant to the secondary loop, the waste heat discharge system's waste discharge pump was in operation, and the boron meter was in operation along the path of "secondary loop inlet water → boron meter → control box".

[0072] 2. Overhaul downlink NS / SG operating mode

[0073] After the overhaul begins, the primary coolant is cooled and depressurized, entering the steam generator cooling shutdown operation mode (NS / SG). According to the operating technical specifications, the boron concentration of the primary coolant under this condition must meet the shutdown boron concentration requirement of ~2500ppm. A boron meter needs to be used to monitor the boron concentration of the primary coolant to ensure that the boron concentration of the primary coolant meets the requirements. Under this condition, the three main pumps are put into operation to circulate and cool the primary coolant, and the capacity control box is put into operation to return the purified primary coolant to the secondary loop. The waste heat removal system's waste discharge pump is in a stopped state, and the boron meter continues to operate along the path of "secondary loop water → boron meter → capacity control box".

[0074] 3. During the overhaul downhill NS / RRA (main pump commissioning phase) operation mode

[0075] The primary coolant continues to cool and depressurize, entering the residual heat removal system for normal shutdown mode (NS / RRA). According to the operating technical specifications, the boron concentration of the primary coolant under this condition must meet the shutdown boron concentration requirement of ~2500ppm. A boron meter needs to be used to monitor the boron concentration of the primary coolant to ensure that the boron concentration of the primary coolant meets the requirements. Under this condition, the three main pumps and the residual heat removal pump are in operation to circulate and cool the primary coolant. The capacity control box is in operation to return the purified primary coolant to the secondary loop. The boron meter continues to operate along the path of "secondary loop water → boron meter → capacity control box".

[0076] 4. During overhaul, the NS / RRA (main pump shutdown phase) operating mode

[0077] The primary coolant continues to cool and depressurize. According to the operating technical specifications, the boron concentration of the primary coolant under this condition must meet the shutdown boron concentration requirement of ~2500ppm. A boron meter needs to be used to monitor the boron concentration of the primary coolant to ensure that the boron concentration of the primary coolant meets the requirements. Under this condition, the three main pumps and the capacity control box are shut down. The waste heat pump is put into operation to circulate and cool and purify the primary coolant. The boron meter operation path needs to be changed to "waste heat discharge system upstream water of heat exchanger → boron meter → second loop".

[0078] Furthermore, after changing the boron meter's operation path to "water upstream of the waste heat discharge system heat exchanger → boron meter → second loop", check whether the boron meter's flow rate is >50L / h.

[0079] Furthermore, if the boron meter flow rate does not meet the requirement of >50L / h, the defect should be investigated according to the rapid troubleshooting plan for when the boron meter operation path of the primary loop coolant is unsuccessful: "waste heat discharge system upstream water of heat exchanger → boron meter → secondary loop".

[0080] Furthermore, based on the defects identified in the troubleshooting plan, the backup plan for the boron meter operation path of the primary loop coolant was selected: "waste heat discharge system upstream water of heat exchanger → boron meter → secondary loop", and the boron meter was put back into operation.

[0081] Furthermore, after restarting the boron meter, check whether the boron meter flow rate is >50L / h.

[0082] 5. Under the overhaul downlink MCS operation mode

[0083] The primary coolant continues to cool and depressurize, entering maintenance shutdown mode (MCS). According to the operating technical specifications, the boron concentration of the primary coolant under this condition must meet the requirement of 2300-2500 ppm. A boron meter needs to be put into operation to monitor the boron concentration of the primary coolant to ensure that the boron concentration of the primary coolant meets the requirements. Under this condition, the three main pumps and the capacity control box are shut down. The waste heat pump is put into operation to circulate and cool and purify the primary coolant. The boron meter continues to operate along the path of "waste heat discharge system upstream water of heat exchanger → boron meter → second loop".

[0084] 6. Under the downlink RCS operation mode during major overhaul

[0085] The refueling pool is filled to 15.5 meters, and the refueling shutdown mode (RCS) is entered. According to the operating technical specifications, the boron concentration of the primary coolant must meet the requirement of 2300-2500 ppm under this condition. A boron meter needs to be put into operation to monitor the boron concentration of the primary coolant to ensure that the boron concentration of the primary coolant meets the requirements. Under this condition, the three main pumps and the capacity control box are shut down. The waste heat pump is put into operation to circulate and cool and purify the primary coolant. The boron meter continues to operate along the path of "waste heat discharge system upstream water of heat exchanger → boron meter → second loop".

[0086] 7. Under the overhaul downlink RCD operating mode

[0087] After the reactor unloading operation is completed, the reactor enters the fully unloaded reactor (RCD) mode. According to the operating technical specifications, there is no requirement for the boron concentration of the first loop coolant under this condition, and the boron meter does not need to be put into operation.

[0088] 8. Before overhauling the uplink RCS operating mode

[0089] After completing overhaul-related maintenance work in Reactor Complete Discharge (RCD) mode, the primary loop system and refueling pool are filled with water, and the residual heat removal system is activated to circulate and purify the primary loop coolant. Because the next step is for the unit to enter Refueling Shutdown (RCS) mode for refueling operations, according to operational specifications, the boron concentration of the primary loop coolant in RCS mode must meet the requirement of 2300–2500 ppm. Therefore, a boron meter needs to be activated in advance to monitor the boron concentration of the primary loop coolant to ensure it meets the 2300–2500 ppm requirement. At this time, the three main pumps and the capacity control box are shut down, and the residual heat removal pump is activated to circulate and purify the primary loop coolant. The boron meter activation path is: "Water upstream of the heat exchanger in the residual heat removal system → boron meter → second loop".

[0090] Furthermore, after changing the boron meter's operation path to "water upstream of the waste heat discharge system heat exchanger → boron meter → second loop", check whether the boron meter's flow rate is >50L / h.

[0091] Furthermore, if the boron meter flow rate does not meet the requirement of >50L / h, the defect should be investigated according to the rapid troubleshooting plan for when the boron meter operation path of the primary loop coolant is unsuccessful: "waste heat discharge system upstream water of heat exchanger → boron meter → secondary loop".

[0092] Furthermore, based on the defects identified in the troubleshooting plan, the backup plan for the boron meter operation path of the primary loop coolant was selected: "waste heat discharge system upstream water of heat exchanger → boron meter → secondary loop", and the boron meter was put back into operation.

[0093] Furthermore, after restarting the boron meter, check whether the boron meter flow rate is >50L / h.

[0094] 9. Overhaul uplink RCS operation mode

[0095] The unit enters the refueling shutdown mode (RCS) for refueling operations. According to the operating technical specifications, the boron concentration of the primary coolant must meet the requirement of 2300-2500 ppm under this condition. A boron meter needs to be used to monitor the boron concentration of the primary coolant to ensure that the boron concentration of the primary coolant meets the requirements. Under this condition, the three main pumps and the capacity control box are shut down. The waste heat pump is put into operation to circulate and cool and purify the primary coolant. The boron meter continues to operate along the path of "waste heat discharge system upstream water of heat exchanger → boron meter → second loop".

[0096] 10. Overhaul uplink MCS operation mode

[0097] The primary coolant is gradually pressurized and enters maintenance shutdown mode (MCS). According to the operating technical specifications, the boron concentration of the primary coolant must meet the requirement of 2300-2500 ppm under this condition. A boron meter needs to be put into operation to monitor the boron concentration of the primary coolant to ensure that the boron concentration of the primary coolant meets the requirements. Under this condition, the three main pumps and the capacity control box are shut down. The waste heat pump is put into operation to circulate and cool and purify the primary coolant. The boron meter continues to operate along the path of "waste heat discharge system upstream water of heat exchanger → boron meter → second loop".

[0098] 11. Overhaul Upward NS / RRA (Main Pump Shutdown Phase) Operation Mode

[0099] The primary coolant continues to heat up and pressurize, entering the normal shutdown mode (NS / RRA) for cooling the residual heat removal system. According to the operating technical specifications, the boron concentration of the primary coolant under this condition must meet the shutdown boron concentration requirement of ~2500ppm. A boron meter needs to be used to monitor the boron concentration of the primary coolant to ensure that the boron concentration of the primary coolant meets the requirements. Under this condition, the three main pumps are shut down, the residual heat removal pump is put into operation to circulate and cool the primary coolant, and the capacity control box is put into operation to return the purified primary coolant to the secondary loop. The boron meter continues to operate along the path of "upstream water from the heat exchanger of the residual heat removal system → boron meter → secondary loop".

[0100] 12. Overhaul Upward NS / RRA (Main Pump Commissioning Phase) Operation Mode

[0101] The primary coolant continues to heat up and pressurize. Once the main pump meets the commissioning conditions, the main pump is put into operation. According to the operating technical specifications, the boron concentration of the primary coolant under this condition must meet the shutdown boron concentration requirement of ~2500ppm. A boron meter needs to be used to monitor the boron concentration of the primary coolant to ensure that the boron concentration of the primary coolant meets the requirements. Under this condition, the three main pumps and the residual discharge pump are put into operation to circulate and cool the primary coolant. The capacity control box is put into operation to return the purified primary coolant to the secondary loop. The boron meter operation path needs to be changed to "secondary loop inlet water → boron meter → capacity control box".

[0102] Furthermore, after changing the boron meter's operation path to "second ring road water inlet → boron meter → capacity control box", check whether the boron meter flow rate is >50L / h.

[0103] Furthermore, if the boron meter flow rate does not meet the requirement of >50L / h, troubleshooting should be carried out according to the rapid troubleshooting plan for abnormalities when the primary loop coolant boron meter commissioning path "second loop water → boron meter → capacity control box" fails.

[0104] Furthermore, based on the defects identified in the troubleshooting plan, the backup plan of "second loop coolant boron meter commissioning path" was selected, namely "second loop water → boron meter → capacity control box", and the boron meter was put back into operation.

[0105] Furthermore, after restarting the boron meter, check whether the boron meter flow rate is >50L / h.

[0106] 13. Overhauling uplink NS / SG operating mode

[0107] The primary coolant continues to heat up and pressurize, entering the steam generator cooling shutdown mode (NS / SG). According to the operating technical specifications, the boron concentration of the primary coolant under this condition must meet the shutdown boron concentration requirement of ~2500ppm. A boron meter needs to be used to monitor the boron concentration of the primary coolant to ensure that the boron concentration of the primary coolant meets the requirements. Under this condition, the three main pumps are in operation to circulate and cool the primary coolant, and the capacity control box is in operation to return the purified primary coolant to the secondary loop. The waste heat discharge system's waste discharge pump is in a stopped state, and the boron meter continues to operate along the path of "secondary loop inlet water → boron meter → capacity control box".

[0108] 14. Overhaul Upward RP Operation Mode

[0109] The unit begins critical operation and enters reactor power operation mode (RP). According to the operating technical specifications, the boron concentration of the primary coolant must meet the critical boron concentration under this condition. A boron meter needs to be used to monitor the boron concentration of the primary coolant to ensure that the boron concentration of the primary coolant meets the requirements. Under this condition, the three main pumps are in operation to circulate and cool the primary coolant, and the capacity control box is in operation to return the purified primary coolant to the secondary loop. The waste heat removal system's waste discharge pump is in a stopped state, and the boron meter continues to operate along the path of "secondary loop inlet water → boron meter → capacity control box".

Claims

1. A control method for activating the primary loop boron meter during a major overhaul of a nuclear power plant unit, characterized in that, Includes the following steps: Step 1: Pre-overhaul procedures; Step Two: Downward Overhaul Procedures; Step 3: Overhaul and upward movement steps.

2. The control method for activating the primary loop boron meter during a nuclear power plant unit overhaul as described in claim 1, characterized in that: Step one includes, (1) Before the overhaul begins - RP operation mode Before the overhaul began, the unit was in reactor power operation mode (RP power operation). According to the operating technical specifications, the boron concentration of the primary coolant in this condition must meet the critical boron concentration. A boron meter was required to monitor the boron concentration of the primary coolant to ensure that the boron concentration of the primary coolant met the requirements. Under this condition, the three main pumps were in operation to circulate and cool the primary coolant, and the control box was in operation to return the purified primary coolant to the secondary loop. The waste heat discharge system's waste discharge pump was in a stopped state, and the boron meter was in operation along the path of "secondary loop inlet water → boron meter → control box".

3. The control method for activating the primary loop boron meter during a nuclear power plant unit overhaul as described in claim 2, characterized in that: Step two includes, (2) Under the overhaul downlink NS / SG operating mode After the overhaul begins, the primary coolant is cooled and depressurized, entering the steam generator cooling shutdown operation mode NS / SG. According to the operational technical specifications, the boron concentration of the primary coolant under this condition must meet the shutdown boron concentration requirement of ~2500ppm. A boron meter must be used to monitor the boron concentration of the primary coolant to ensure it meets the requirements. Under this condition, the three main pumps are in operation to circulate and cool the primary coolant, and the capacity control tank returns the purified primary coolant to the secondary loop. The waste heat removal system's waste heat pump is shut down, and the boron meter continues to operate along the path of "secondary loop inlet water → boron meter → capacity control tank". (3) During the commissioning phase of the NS / RRA main pump during major overhaul, the operating mode is as follows: The primary coolant continues to cool and depressurize, entering the residual heat removal system to cool the NS / RRA (Normal Shutdown / Remote Recirculation) system during normal shutdown. According to operational specifications, the boron concentration in the primary coolant under this condition must meet the shutdown boron concentration requirement of ~2500 ppm. A boron meter must be used to monitor the boron concentration in the primary coolant to ensure it meets the requirements. Under this condition, the three main pumps and the residual heat pump are in operation to circulate and cool the primary coolant. The capacity control tank returns the purified primary coolant to the secondary loop. The boron meter continues to operate along the path of "secondary loop inlet water → boron meter → capacity control tank." (4) During the downlink NS / RRA-main pump shutdown phase of the overhaul, the operating mode is as follows: The primary coolant continues to cool and depressurize. According to the operating technical specifications, the boron concentration of the primary coolant under this condition must meet the shutdown boron concentration requirement of ~2500ppm. A boron meter needs to be used to monitor the boron concentration of the primary coolant to ensure that the boron concentration of the primary coolant meets the requirements. Under this condition, the three main pumps and the capacity control box are shut down, and the waste heat pump is put into operation to circulate, cool, and purify the primary coolant. The boron meter operation path needs to be changed to "residual heat discharge system upstream water from the heat exchanger → boron meter → second loop". (5) Under the overhaul downlink MCS operation mode The primary coolant continues to cool and depressurize, entering the maintenance shutdown mode (MCS). According to the operational technical specifications, the boron concentration of the primary coolant under this condition must meet the requirement of 2300–2500 ppm. A boron meter needs to be used to monitor the boron concentration of the primary coolant to ensure that the boron concentration meets the requirements. Under this condition, the three main pumps and the capacity control box are shut down. The waste heat pump is put into operation to circulate, cool, and purify the primary coolant. The boron meter continues to operate along the path of "waste heat discharge system upstream water from the heat exchanger → boron meter → second loop". (6) Under the overhaul downlink RCS operation mode The refueling pool is filled to 15.5 meters, and the reactor enters the refueling shutdown mode (RCS). According to the operational technical specifications, the boron concentration of the primary coolant must meet the requirement of 2300–2500 ppm under this condition. A boron meter must be used to monitor the boron concentration of the primary coolant to ensure that the boron concentration meets the requirements. Under this condition, the three main pumps and the capacity control box are shut down. The waste heat pump is put into operation to circulate and cool the primary coolant for purification. The boron meter continues to operate along the path of "waste heat discharge system upstream water of heat exchanger → boron meter → second loop". (7) Under the overhaul downlink RCD operation mode After the reactor unloading operation is completed, the reactor enters the full unloading mode (RCD). According to the operating technical specifications, there is no requirement for the boron concentration of the first loop coolant under this condition, and the boron meter does not need to be put into operation.

4. The control method for activating the primary loop boron meter during a nuclear power plant unit overhaul as described in claim 3, characterized in that: Step (4) includes After changing the boron meter's operation path to "water upstream of the waste heat discharge system heat exchanger → boron meter → second loop", check if the boron meter's flow rate is greater than 50 L / h. If the boron meter flow rate does not meet the requirement of >50L / h, troubleshoot the defect according to the rapid troubleshooting plan for when the primary loop coolant boron meter commissioning path "waste heat discharge system upstream water of heat exchanger → boron meter → secondary loop" fails. Based on the defects identified in the troubleshooting plan, the backup plan was selected: "waste heat discharge system upstream water from heat exchanger → boron meter → second loop". The boron meter was then put back into operation. After restarting the boron meter, check if the flow rate of the boron meter is greater than 50L / h.

5. The control method for activating the primary loop boron meter during a nuclear power plant unit overhaul as described in claim 4, characterized in that: Step three includes, (8) Before overhauling the uplink RCS operation mode After the unit completes its overhaul-related maintenance work in the reactor fully unloaded mode (RCD), the primary loop system and refueling pool are filled with water, and the residual heat removal system is activated to circulate and purify the primary loop coolant. Because the next step is for the unit to enter the refueling shutdown mode (RCS) for refueling operations, according to operational specifications, the boron concentration of the primary loop coolant in the RCS refueling shutdown mode must meet the requirement of 2300–2500 ppm. Therefore, a boron meter needs to be activated in advance to monitor the boron concentration of the primary loop coolant to ensure that it meets the 2300–2500 ppm requirement. At this time, the three main pumps and the capacity control box are shut down, and the residual heat removal pump is activated to circulate and purify the primary loop coolant. The boron meter activation path is: "upstream water from the heat exchanger of the residual heat removal system → boron meter → second loop". (9) Overhaul uplink RCS operation mode The unit enters the refueling shutdown mode (RCS) for refueling operations. According to the operational technical specifications, the boron concentration of the primary coolant must be between 2300 and 2500 ppm under this condition. A boron meter must be used to monitor the boron concentration of the primary coolant to ensure that it meets the requirements. Under this condition, the three main pumps and the capacity control box are shut down. The waste heat pump is in operation to circulate and purify the primary coolant. The boron meter continues to operate along the path of "waste heat discharge system upstream water from the heat exchanger → boron meter → secondary loop". (10) Overhaul uplink MCS operation mode The primary coolant is gradually pressurized, entering the maintenance shutdown mode (MCS). According to the operational technical specifications, the boron concentration of the primary coolant under this condition must meet the requirement of 2300–2500 ppm. A boron meter needs to be used to monitor the boron concentration of the primary coolant to ensure that the boron concentration meets the requirements. Under this condition, the three main pumps and the capacity control tank are shut down. The waste heat pump is put into operation to circulate and cool the primary coolant for purification. The boron meter continues to operate along the path of "waste heat discharge system upstream water from the heat exchanger → boron meter → second loop". (11) During the overhaul and NS / RRA main pump shutdown phase, the operating mode is as follows: The primary coolant continues to heat and pressurize, entering the residual heat removal system to cool the NS / RRA (Normal Shutdown / Remote Recirculation) system during normal shutdown. According to operational specifications, the boron concentration in the primary coolant under this condition must meet the shutdown boron concentration requirement of ~2500 ppm. A boron meter must be used to monitor the boron concentration in the primary coolant to ensure it meets the requirements. Under this condition, the three main pumps are shut down, and the residual heat removal pumps are activated to circulate and cool the primary coolant. The control tank is activated to return the purified primary coolant to the secondary loop. The boron meter continues to operate along the path of "upstream water from the heat exchanger in the residual heat removal system → boron meter → secondary loop". (12) During the overhaul and commissioning of the NS / RRA main pump, the operating mode is as follows: The primary coolant continues to heat and pressurize. Once the main pumps meet the commissioning conditions, they are put into operation. According to the operating technical specifications, the boron concentration of the primary coolant under this condition must meet the shutdown boron concentration requirement of ~2500ppm. A boron meter needs to be used to monitor the boron concentration of the primary coolant to ensure that it meets the requirements. Under this condition, the three main pumps and the residual discharge pump are in operation to circulate and cool the primary coolant. The capacity control box is in operation to return the purified primary coolant to the secondary loop. The boron meter operation path needs to be changed to "secondary loop inlet water → boron meter → capacity control box". (13) Overhaul uplink NS / SG operation mode The primary coolant continues to heat and pressurize, entering the steam generator cooling shutdown mode NS / SG. According to the operational technical specifications, the boron concentration of the primary coolant under this condition must meet the shutdown boron concentration requirement of ~2500ppm. A boron meter must be used to monitor the boron concentration of the primary coolant to ensure it meets the requirements. Under this condition, the three main pumps are in operation to circulate and cool the primary coolant. The capacity control tank returns the purified primary coolant to the secondary loop. The waste heat removal system's waste discharge pumps are shut down. The boron meter continues to operate along the path of "secondary loop inlet water → boron meter → capacity control tank". (14) Overhauling Upward RP Operation Mode The unit begins critical operation and enters reactor power operation mode (RP). According to the operating technical specifications, the boron concentration of the primary coolant must meet the critical boron concentration under this condition. A boron meter needs to be used to monitor the boron concentration of the primary coolant to ensure that the boron concentration of the primary coolant meets the requirements. Under this condition, the three main pumps are in operation to circulate and cool the primary coolant, and the capacity control box is in operation to return the purified primary coolant to the secondary loop. The waste heat removal system's waste discharge pump is in a stopped state, and the boron meter continues to operate along the path of "secondary loop inlet water → boron meter → capacity control box".

6. The control method for activating the primary loop boron meter during a nuclear power plant unit overhaul as described in claim 5, characterized in that: Step (8) includes, After changing the boron meter's operation path to "water upstream of the waste heat discharge system heat exchanger → boron meter → second loop", check if the boron meter's flow rate is greater than 50 L / h. If the boron meter flow rate does not meet the requirement of >50L / h, troubleshoot the defect according to the rapid troubleshooting plan for when the primary loop coolant boron meter commissioning path "waste heat discharge system upstream water of heat exchanger → boron meter → secondary loop" fails. Based on the defects identified in the troubleshooting plan, the backup plan was selected: "waste heat discharge system upstream water from heat exchanger → boron meter → second loop". The boron meter was then put back into operation. After restarting the boron meter, check if the flow rate of the boron meter is greater than 50L / h.

7. The control method for activating the primary loop boron meter during a nuclear power plant unit overhaul as described in claim 6, characterized in that: Step (12) includes, After changing the boron meter's operation path to "second ring road water inlet → boron meter → capacity control box", check if the boron meter's flow rate is greater than 50L / h. If the boron meter flow rate does not meet the requirement of >50L / h, troubleshoot the defect according to the rapid troubleshooting plan for when the primary loop coolant boron meter commissioning path "second loop water inlet → boron meter → capacity control box" fails. Based on the defects identified in the troubleshooting plan, the backup plan for the boron meter operation path of the primary coolant circuit was selected: "second loop water inlet → boron meter → capacity control box". The boron meter was then put back into operation. After restarting the boron meter, check if the flow rate of the boron meter is greater than 50L / h.

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