Method for overhauling reactor cavity pool, primary loop pipeline connected with reactor cavity pool and built-in refueling water tank during reactor overhaul

Abstract

The invention discloses a method for overhauling a reactor cavity pool, a primary loop pipeline connected with the reactor cavity pool and a built-in refueling water tank during the overhaul period of a reactor. The method comprises the following steps: S1, putting a unit to be overhauled in a reactor complete unloading mode; s2, in a complete discharging mode of the reactor, at least part of water in a reactor cavity pool of the to-be-overhauled unit and a primary loop pipeline connected with the reactor cavity pool is discharged to a built-in refueling water tank of the to-be-overhauled unit, meanwhile, water in the built-in refueling water tank is discharged to a water storage unit, and the water storage unit comprises a coolant storage tank of the to-be-overhauled unit, a reactor pit water injection tank and a loading well; and S3, carrying out parallel maintenance on the reactor cavity pool, the primary loop pipeline connected with the reactor cavity pool and the built-in refueling water tank. The extra water storage unit is introduced as the water storage container of the built-in refueling water tank, so that parallel drainage and parallel maintenance of the reactor cavity pool, the primary loop pipeline connected with the reactor cavity pool and the built-in refueling water tank are realized, and the construction period of the reactor overhaul period can be effectively shortened.

Description

Technical Field

[0001] The present invention relates to the technical field of nuclear power plant overhaul, and in particular to a method for overhauling a reactor cavity pool and its connected primary loop pipelines and internal refueling water tanks during reactor overhaul. Background Art

[0002] Reactor overhaul is a systematic overhaul carried out according to the equipment aging laws and technical specifications and on a planned shutdown basis. The reactor water pool includes the reactor cavity pool (or refueling cavity) and the in-core component storage pool. During the reactor overhaul, in the reactor full unloading mode, it is necessary to use the internal refueling water tank to receive and store water from the reactor cavity pool and the primary circuit pipes connected thereto, so as to carry out overhaul of the reactor cavity pool and the primary circuit pipes connected thereto. However, since the internal refueling water tank also needs to be overhauled, the overhaul items include corrective maintenance of the valves at the bottom of the internal refueling water tank and in-service inspections, etc. Therefore, according to the current overhaul process, the reactor cavity pool and the internal refueling water tank cannot be overhauled at the same time. The two can only be overhauled in series, that is, the reactor cavity pool and the primary circuit pipes connected thereto are overhauled first, and then the internal refueling water tank is overhauled, resulting in a longer reactor overhaul period. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide an improved method for inspecting and repairing a reactor cavity pool and its connected primary circuit piping and internal refueling water tank during reactor overhaul, so as to reduce the reactor overhaul period.

[0004] The technical solution adopted by the present invention to solve the technical problem is to construct a method for repairing the reactor cavity pool and its connected primary circuit pipeline and internal refueling water tank during reactor overhaul, which includes the following steps:

[0005] S1. Place the unit to be overhauled in the reactor complete unloading mode;

[0006] S2. In the reactor complete unloading mode, at least partially discharge the water in the reactor cavity pool of the unit to be overhauled and the primary loop pipeline connected thereto into the internal refueling water tank of the unit to be overhauled, and simultaneously discharge the water in the internal refueling water tank into a water storage unit, the water storage unit comprising the coolant storage tank, the reactor pit water injection tank, and the loading well of the unit to be overhauled;

[0007] S3. After the reactor cavity pool, the primary loop pipe connected thereto, and the internal refueling water tank are emptied in parallel, the reactor cavity pool, the primary loop pipe connected thereto, and the internal refueling water tank are inspected and repaired in parallel.

[0008] In some embodiments, in step S2, discharging at least part of the water in the reactor cavity pool of the unit to be overhauled and the primary loop pipe connected thereto into the internal refueling water tank comprises the following steps:

[0009] S201, the water in the primary circuit pipe connected to the reactor cavity pool is discharged to the internal refueling water tank through the hot pipe section (62) of the safety injection system; at the same time, the water in the reactor cavity pool is discharged to the internal refueling water tank through the gravity drain line (63) until the reactor cavity pool and the primary circuit connected thereto reach the low water level;

[0010] S202. After the reactor cavity pool and the primary loop connected thereto reach the low water level, the water in the transition section of the primary loop pipe connected to the reactor cavity pool flows to the nuclear island drain system through the primary loop transition section drain pipe, and is then pumped to the coolant storage and treatment system through the nuclear island drain system.

[0011] In some embodiments, in step S2 , discharging the water in the built-in replacement water tank to the coolant storage tank includes: discharging the water in the built-in replacement water tank to the coolant storage tank through a short circulation line and a low-pressure drain line of a chemical and volume control system.

[0012] In some embodiments, in step S2, discharging the water in the internal displacement water tank to the coolant storage tank comprises the following steps:

[0013] S211. Introducing a new drainage pipeline, wherein one end of the new drainage pipeline is connected to pipelines of the reactor water pool and fuel water pool cooling and treatment system, and the other end of the new drainage pipeline is connected to the coolant storage tank;

[0014] S212: Drain the water in the internal replacement water tank to the coolant storage tank through the newly added drainage pipeline.

[0015] In some embodiments, in step S2, while the water in the internal replacement water tank is discharged to the coolant storage tank, the water in the coolant storage tank flows to the boron recovery system, and the boron recovery system simultaneously performs boron-water separation.

[0016] In some embodiments, in step S2, discharging the water in the built-in refueling water tank to the reactor pit water injection tank includes: discharging the water in the built-in refueling water tank to the reactor pit water injection tank through pipelines of the reactor water pool and fuel water pool cooling and treatment system.

[0017] In some embodiments, in step S2, discharging the water in the built-in refueling water tank to the loading well includes: discharging the water in the built-in refueling water tank to the loading well through pipelines of the reactor water pool and fuel water pool cooling and treatment system.

[0018] In some embodiments, the water storage unit further includes a loading well of an adjacent unit to the unit to be overhauled.

[0019] In some embodiments, discharging the water in the built-in refueling water tank to the loading well of the adjacent unit of the unit to be overhauled includes: discharging the water in the built-in refueling water tank to the loading well of the adjacent unit of the unit to be overhauled through the nuclear island waste liquid discharge system shared by the adjacent units.

[0020] In some embodiments, discharging the water in the internal refueling water tank to the loading well of the adjacent unit to be overhauled through the nuclear island waste liquid discharge system shared by the adjacent units comprises the following steps:

[0021] S221, draining the water in the internal refueling water tank of the unit to be overhauled into the pipeline of the nuclear island waste liquid discharge system, flushing the pipeline of the nuclear island waste liquid discharge system, and discharging the flushed water into the water storage tank of the nuclear island waste liquid discharge system;

[0022] S222, confirm whether the water quality of the internal replacement water tank of the unit to be repaired is qualified, if so, execute step S223;

[0023] S223. The water in the internal refueling water tank of the unit to be overhauled is transferred to the loading well of the adjacent unit of the unit to be overhauled through the pipeline of the nuclear island waste liquid discharge system.

[0024] The present invention has at least the following beneficial effects: by introducing an additional water storage unit as a water storage container for the internal refueling water tank, the present invention realizes parallel drainage and parallel maintenance of the reactor cavity pool and its connected primary loop pipeline, and the internal refueling water tank, thereby effectively shortening the construction period during the reactor overhaul. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solution of the present invention, the present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0026] Figure 1 It is a flowchart of a method for repairing a reactor cavity pool and its connected primary loop piping and internal refueling water tank during a reactor overhaul according to the present invention;

[0027] Figure 2 This is a schematic diagram of the connection methods and water volume of some facilities in the nuclear power plant before the reactor is completely unloaded;

[0028] Figure 3 This is a schematic diagram of the connection methods and water volume of some facilities in the nuclear power plant after the reactor is completely unloaded and the primary water circuit is drained;

[0029] Figure 4 This is a schematic diagram of the connection pipeline between the safety injection system and the internal displacement water tank;

[0030] Figure 5 It is a schematic diagram of the connecting pipelines of some facilities and systems in the same unit of a nuclear power plant;

[0031] Figure 6 It is a schematic diagram of the connecting pipelines of some facilities and systems in the same unit of a nuclear power plant;

[0032] Figure 7 It is a schematic diagram of the connecting pipelines of some facilities and systems in the same unit of a nuclear power plant;

[0033] Figure 8 It is a schematic diagram of the connecting pipelines of some facilities and systems in the same unit of a nuclear power plant;

[0034] Figure 9 It is a schematic diagram of the connecting pipelines of some facilities and systems in the same unit of a nuclear power plant;

[0035] Figure 10 Schematic diagram of connecting pipelines of some facilities and systems in the unit to be repaired in some embodiments of the present invention;

[0036] Figure 11 yes Figure 10 The diagram shows the connecting pipelines of some facilities and systems in the adjacent units of the unit to be repaired. DETAILED DESCRIPTION

[0037] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described in detail with reference to the accompanying drawings.

[0038] The unit is the smallest power generation unit in a nuclear power plant, and each unit contains a complete set of nuclear power generation systems. Each unit can operate independently without affecting each other. Each unit is equipped with an independent reactor water pool and fuel water pool cooling and treatment system (referred to as PTR), a coolant storage and treatment system (referred to as TEP), a chemical and volume control system (referred to as RCV), a safety injection system (RIS), etc. Among them, RIS includes an internal refueling water tank 1 (referred to as IRWST), a power pump and related pipelines, etc. The water stored in the internal refueling water tank 1 serves as the water source of RIS, continuously cooling the core under accident conditions to prevent the pressure vessel from melting through. TEP includes a coolant storage tank 41 and related power pumps, pipelines, etc. PTR is mainly used to ensure the long-term cooling of the spent fuel element storage pool, as well as the injection, drainage and purification of the reactor water pool. The reactor water pool includes a reactor cavity pool 21 (or refueling cavity) and an in-core component storage pool 22. There is a sluice gate between the reactor cavity pool 21 and the in-core component storage pool 22, which can control the connection and isolation between the two. Before the reactor is completely unloaded, the reactor cavity pool 21 needs to use the two purification pumps 5 of the PTR to draw water from the internal refueling water tank 1 and fill it to the normal liquid level of 17m in order to carry out the core refueling operation. After the core refueling operation is completed, the reactor enters the complete unloading mode. In the complete unloading mode of the reactor, the reactor cavity pool 21 and the first-loop pipe 3 connected thereto need to be emptied in order to overhaul the two, wherein the internal refueling water tank 1 serves as a temporary storage container for the water discharged from the reactor cavity pool 21 and the first-loop pipe 3 connected thereto. When the overhaul of the reactor cavity pool 21 and the first-loop pipe 3 connected thereto is completed, the water in the internal refueling water tank 1 is returned to the reactor cavity pool 21 and the first-loop pipe 3 connected thereto so that the internal refueling water tank 1 can be overhauled. Therefore, in the existing maintenance process, the reactor cavity pool 21 and its connected primary circuit piping 3, as well as the internal refueling water tank 1, serve as each other's water storage containers. Therefore, they can only be repaired in series, which results in a long construction period during the overhaul and is not conducive to achieving the goal of a 60-day construction period for a ten-year overhaul. The present invention aims to optimize the maintenance process of the reactor cavity pool 21 and the internal refueling water tank 1 during reactor overhauls, with the goal of shortening the construction period.

[0039] See also Figure 1 The present invention shows a flowchart of a method for overhauling a reactor cavity pool and its connected primary circuit piping and internal refueling water tank during a reactor overhaul (hereinafter referred to as the overhaul method for ease of understanding). The overhaul method includes the following steps:

[0040] S1. Place the unit to be overhauled in the reactor complete unloading mode.

[0041] S2. In the reactor complete unloading mode, at least a portion of the water in the reactor cavity pool 21 and the connected primary-loop pipeline 3 of the unit to be repaired is discharged into the internal refueling water tank 1. Simultaneously, the water in the internal refueling water tank 1 is discharged into a water storage unit, which includes the coolant storage tank 41, the reactor pit water injection tank 42, and the loading well 43 of the unit to be repaired. For example, when Unit 3 of a nuclear power plant needs to be repaired, Unit 3 first enters the reactor complete unloading mode. Then, the water in the reactor cavity pool 21 and the connected primary-loop pipeline 3 of Unit 3 is discharged into the internal refueling water tank 1. Simultaneously, the water in the internal refueling water tank 1 is discharged into the coolant storage tank 41, the reactor pit water injection tank 42, and the loading well 43 of Unit 3. In other words, the two processes of discharging the water in the reactor cavity pool 21 and the connected primary-loop pipeline 3 into the internal refueling water tank 1 and discharging the water in the internal refueling water tank 1 into the water storage unit can be performed simultaneously. In other words, by introducing an additional water storage unit as a water storage container for the internal refueling water tank 1 , the reactor cavity pool 21 and the primary loop pipe 3 connected thereto, and the internal refueling water tank 1 can be drained in parallel.

[0042] S3: After the reactor cavity pool 21 and its connected primary circuit piping 3 and internal refueling water tank 1 are emptied in parallel, the reactor cavity pool 21 and its connected primary circuit piping 3 and internal refueling water tank 1 are inspected and repaired in parallel. Specifically, after step S2 is completed, the reactor cavity pool 21 and its connected primary circuit piping 3 and internal refueling water tank 1 have all been emptied. At this time, the reactor cavity pool 21 and its connected primary circuit piping 3 and internal refueling water tank 1 can be inspected and repaired simultaneously, thereby shortening the construction period.

[0043] In summary, the present invention realizes the parallel drainage and parallel maintenance of the reactor cavity pool 21 and its connected one-loop pipeline 3, and the internal refueling water tank 1 by introducing an additional water storage unit as a water storage container for the internal refueling water tank 1, thereby being able to effectively shorten the construction period during the reactor overhaul. According to experiments, the maintenance method of the present invention can reduce the overhaul critical path construction period by 9 days. Based on the calculation that a unit generates 10 million yuan of full-power electricity per day, the economic benefits can be increased by nearly 90 million yuan, which is also conducive to achieving the goal of an excellent construction period of 60 days for a ten-year overhaul. In addition, the above-mentioned coolant storage tank 41, the reactor pit water injection tank 42 and the loading well 43 are existing facilities of the unit to be overhauled, which will not introduce additional modification costs to the nuclear power plant, and are easier to implement and have wider applicability. Through the following detailed analysis and research process, the feasibility of using the coolant storage tank 41, the reactor pit water injection tank 42 and the loading well 43 as water storage containers for the internal refueling water tank 1 was determined:

[0044] Under normal operating conditions of the reactor, the water in the internal refueling water tank 1 is usually maintained at 1890~1999m 3 Assuming the reactor enters overhaul, at the beginning of shutdown, the water volume in the internal refueling water tank 1 is 1940m 3 .

[0045] like Figure 2 As shown, before the reactor is completely unloaded, the reactor cavity pool 21 needs to use two purification pumps 5 of the PTR to draw water from the internal refueling water tank 1 and fill it to the normal liquid level of 17m in order to carry out the core refueling operation. At this time, there are 1785m 3 The water flows from the internal refueling water tank 1 to the reactor cavity pool 21. Based on the new safety analysis and technical specifications, the water volume in the internal refueling water tank 1 should be greater than 800m3 when the four-pool unit is refueling. 3 Therefore, during the process of filling the reactor pool 21 with water from the internal refueling water tank 1, the water in the reactor pit water injection tank 42 needs to be discharged into the internal refueling water tank 1. Comprehensive analysis shows that during the period of full water unloading of the reactor pool, the water loading capacity of each user facility is shown in Table 1 below:

[0046] Facility Name <![CDATA[Volume of water contained (m 3 )]]> Built-in replacement water tank 862 Pit water injection tank 0 Coolant storage tank 1110 / 1120 / 1130BA- 0 Coolant storage tank 1140 / 1150 / 1160BA- 0 Cavity pool 732 Internals storage pool 933 PTR transfer well 330 Loading well of the PTR 0

[0047] Table 1

[0048] like Figure 3 As shown in the figure, after the reactor is completely unloaded, the reactor cavity pool 21 and the connected primary circuit pipe 3 need to be inspected and repaired. After the water gate is installed between the reactor cavity pool 21 and the reactor internal component storage pool 22, the water in the reactor cavity pool 21 and the connected primary circuit pipe 3 is drained to the internal refueling water tank 1 through the drainage line at the bottom, so that the water level of the reactor cavity pool 21 and the connected primary circuit is reduced to the flange surface water level (referring to the water level being reduced to the position of the large cover flange of the reactor pressure vessel 30). This process takes about 832m 3 The water enters the internal refueling water tank 1 (including the reactor cavity pool 21732m 3 And 100m of water above the flange surface of the primary circuit 3 After the core is completely unloaded, in order to inspect the primary circuit pipe 3 and related equipment, it is necessary to drain the water in the primary circuit pipe 3 into the replacement water tank 1. The water volume in the primary circuit pipe 3 is about 75m 3 At this time, the remaining water volume in the internal replacement water tank 1 is about 862+832+75=1769m 3 .

[0049] It should be noted that the coolant storage tank 41 is part of the TEP system; the reactor pit water injection tank 42 is part of the containment heat removal system (EHR); and the loading well 43 is part of the PTR system. The coolant storage tanks 41 have been gradually emptied during the unit's descent to the completion of core unloading. There are six coolant storage tanks 41, each with a total volume of 137m 3 , effective volume 125m 3 , allowing to fill to the highest level 130m 3 The water volume alarm value of the pit water injection tank 42 is 754~770m3 The loading well 43 is kept empty during the overhaul period. The total available water storage capacity of the above facilities is shown in Table 2 below:

[0050] Facility Name <![CDATA[Available water storage volume (m 3 )]]> Coolant storage tank 6*130＝780 Pit water injection tank 770 loading well 330 total 1880

[0051] Table 2

[0052] It can be seen that when the reactor cavity pool 21 and the primary circuit pipe 3 connected thereto are emptied, the available water storage capacity (1880m 3 ) is greater than the remaining water volume in the internal replacement water tank 1 (1769m 3 ), in theory, it is feasible to use the coolant storage tank 41, the pile pit water injection tank 42 and the loading well 43 as water storage containers for the internal replacement water tank 1.

[0053] The water storage unit is only used as a temporary water storage container. After the internal refueling water tank 1 is repaired, the water in the water storage unit needs to be returned to the internal refueling water tank 1. Specifically, in some embodiments, the repair method further includes step S4, after the internal refueling water tank 1 is repaired, the water in the water storage unit is returned to the internal refueling water tank 1.

[0054] As for the water discharge path within the reactor cavity pool 21 and the primary-loop pipeline 3 connected thereto, the prior art utilizes a low-pressure discharge line 61 between the reactor cavity pool 21 and the TEP to drain the reactor cavity pool 21 and the primary-loop pipeline 3 connected thereto until the primary-loop liquid level is lowered to the mid-plane water level. The drainage flow rate of the low-pressure discharge line 61 is relatively small, and this process takes approximately 9 hours of construction time.

[0055] In some embodiments, in step S2, discharging the water in the reactor cavity pool 21 of the unit to be repaired and the primary loop pipe 3 connected thereto into the internal refueling water tank 1 includes the following steps:

[0056] S201、 Figure 4 and Figure 5 As shown, the water in the primary loop pipe 3 connected to the reactor cavity pool 21 is discharged to the internal refueling water tank 1 through the hot pipe section 62 of the safety injection system (RIS); at the same time, the water in the reactor cavity pool 21 is discharged through the gravity drain line 63 (refer to Figure 5 The green pipeline in the figure is discharged to the internal refueling water tank 1 until the reactor cavity pool 21 and the primary circuit connected to it reach the low water level.

[0057] After the reactor cavity pool 21 and the primary circuit connected to it reach the low water level, the transition section of the primary circuit pipe 3 needs to be drained. The transition section of the primary circuit pipe 3 cannot be drained using the heat pipe section 62 of the RIS system, so the drainage path needs to be changed as follows:

[0058] After the reactor pool 21 and its connected primary circuit reach the low water level, water in the transition section of the primary circuit pipe 3 connected to the reactor pool 21 flows through the primary circuit transition section drain pipe to the nuclear island drain system, and is then pumped through the nuclear island drain system to the coolant storage and treatment system (TEP). The primary circuit transition section drain pipe is an existing pipe in the nuclear power unit.

[0059] That is, through step S201, all the water in the reactor cavity pool 21 and a portion of the water in the primary-loop pipeline 3 are discharged to the internal refueling water tank 1 via the gravity drain line 63 and the safety injection system hot pipe segment 62, respectively. Through step S202, the remaining water in the primary-loop pipeline 3 (i.e., the water in the transition section of the primary-loop pipeline 3) flows through the primary-loop transition section drain line to the nuclear island drain system and TEP for treatment. Because the safety injection system hot pipe segment 62 enables reverse gravity drainage of the primary-loop pipeline 3 to the internal refueling water tank 1, the construction period is reduced to approximately 2.5 hours, saving 6.5 hours compared to the 9 hours required for drainage via the previous low-pressure downpipe 61.

[0060] Since the hot pipe section 62 of the safety injection system (RIS) is used to realize the reverse gravity drainage of the primary circuit pipe 3 to the inward displacement tank 1, if the power pump of the RIS continues to run, it will cause damage to the power pump. Therefore, in some embodiments, before step 201, step S200 is further included to connect the medium-pressure injection pump 71 and the low-pressure injection pump 72 of the RIS (see Figure 4 ) is powered off and isolated, thereby avoiding damage to the medium and low pressure injection pump 72 when the hot pipe section 62 of the RIS is used to realize the reverse gravity drainage of the primary circuit pipeline 3 inwardly displacing the material water tank 1.

[0061] In some embodiments, regarding the drainage path from the internal refueling water tank 1 to the coolant storage tank 41, a non-modification solution can be adopted, that is, the original pipeline of the unit is used as the drainage path, without introducing new modification costs for the unit. Specifically, Figure 6 As shown, in step S2, discharging the water in the internal replacement water tank 1 to the coolant storage tank 41 may include: discharging the water in the internal replacement water tank 1 through the short circulation pipeline 64 and the low pressure drain pipeline 61 (reference Figure 6The red dotted line pipeline in the figure is discharged to the coolant storage tank 41. Among them, the two ends of the short circulation pipeline 64 are respectively connected to the official pipeline of the PTR and the low-pressure discharge pipeline 61, and the end of the low-pressure discharge pipeline 61 away from the short circulation pipeline 64 is connected to the coolant storage tank 41. The RCV pump is arranged on the short circulation pipeline 64 as a water transmission power source for the short circulation pipeline 64. The advantage of the above-mentioned non-modification scheme is that the existing pipelines of the unit are used without introducing additional modification costs. However, the above-mentioned non-modification scheme needs to occupy the short circulation pipeline 64 and the low-pressure discharge pipeline 61 of the RCV system, and the drainage flow of the RCV system is 30m 3 / h, the drainage rate is low, and the RCV system is also a key system during the reactor overhaul. Occupying the short circulation pipeline 64 and the low-pressure drain pipeline 61 of the RCV system will cause the maintenance schedule of the RCV system to be postponed.

[0062] In other embodiments, a modification solution may be adopted for the drainage path from the internal refueling water tank 1 to the coolant storage tank 41, that is, a new pipeline is added to the unit for draining water from the internal refueling water tank 1 to the coolant storage tank 41. Specifically, Figure 7 As shown, in step S2, discharging the water in the internal displacement water tank 1 to the coolant storage tank 41 may include the following steps:

[0063] S211, introduce new drainage pipeline 65 (reference Figure 7 The new drainage line 65 is connected to the reactor pool and fuel pool cooling and treatment system (PTR) pipeline (refer to Figure 6 and Figure 7 The other end of the newly added drainage line 65 is connected to the coolant storage tank 41; specifically, the newly added drainage line 65 includes a pipeline and a valve provided on the pipeline.

[0064] S212 , draining the water in the internal replacement water tank 1 to the coolant storage tank 41 through the newly added drainage pipeline 65 .

[0065] The advantage of the above-mentioned transformation scheme is that, by utilizing the power of the purification pump 5 of the PTR system, the water flow rate of the newly added drainage pipeline 65 can reach a maximum of 90m 3 / h, greatly increasing the water transfer rate.

[0066] Specifically, if Figure 6 and Figure 7As shown, the PTR system has two purge pumps 5 (respectively, a first purge pump 5 and a second purge pump 5), a purification unit 87, and related pipeline valve components. The pipeline valve component includes a first pipeline 81, a second pipeline 82, a third pipeline 83, a fourth pipeline 84, a first valve 85, and a second valve 86. The purification unit 87 includes a filter. The first pipeline 81 is connected between the internal replacement water tank 1 and one of the purge pumps 5 (e.g., the first purge pump 5). The second pipeline 82 is connected between one of the purge pumps 5 (e.g., the first purge pump 5) and the purification unit 87. One end of the third pipeline 83 is connected to the purification unit 87, and the other end corresponds to the internal replacement water tank 1. The other end can be connected to the internal replacement water tank 1 or placed above the opening of the internal replacement water tank 1. The fourth pipeline 84 is connected between the second pipeline 82 and the third pipeline 83. The first valve 85 is arranged on the fourth pipeline 84. The second valve 86 is arranged on the third pipeline 83, and the second valve 86 is located between the purification unit 87 and the interface where the fourth pipeline 84 connects to the third pipeline 83. One end of the newly added drainage line 65 is connected to the third pipe 83 and is located between the first valve 85 and the second valve 86 . The other end of the newly added drainage line 65 is connected to the coolant storage tank 41 .

[0067] Furthermore, after the internal refueling water tank 1 is overhauled, the water in the coolant storage tank 41 is returned to the internal refueling water tank 1 by using the desalted water pipe at the outlet of the coolant storage tank 41, the desalted water pump 73 of the reactor boron and water supply system (REA), and the pipeline of the PTR. Figure 6 and Figure 7 The green pipeline in the

[0068] It should be noted that the "water" mentioned in this article generally refers to boric acid-containing water. The boron recovery system in a nuclear power plant is a key system for safe operation and environmental management. Its core function is to process boron-containing coolant, recover boric acid resources, and reduce the discharge of radioactive waste.

[0069] In some embodiments, in step S2, while the water in the internal replacement water tank 1 is discharged to the coolant storage tank 41, the water in the coolant storage tank 41 flows to the boron recovery system, and the boron recovery system simultaneously performs boron-water separation. The rate of boron-water separation is 8.3m 3 / h, and can separate 108m3 within 13 hours of receiving time 3 The boron water is used as the water storage margin of the coolant storage tank 41, thereby increasing the water storage capacity of the coolant storage tank 41, thereby being able to receive more boron water from the internal displacement water tank 1.

[0070] like Figure 8As shown, in some embodiments, in step S2, discharging the water in the internal refueling water tank 1 to the reactor pit water injection tank 42 includes: discharging the water in the internal refueling water tank 1 through the pipeline of the reactor water pool and the fuel water pool cooling and treatment system (PTR) (refer to Figure 8 The water is discharged to the reactor pit water injection tank 42 (the red solid line pipeline in the middle). The structure of the reactor pit water injection tank 42 is concrete lined with stainless steel lining. It is arranged in the reactor building, with a bottom elevation of +7.06m, a fan-shaped bottom, a bottom area of 92.68m2, and an effective volume of approximately 730m 3 During the reactor pool filling period, about 730m3 of water in the reactor pit injection tank 42 3 All the boron water is fed into the internal refueling water tank 1, leaving the reactor pit injection tank 42 empty. Therefore, the PTR's purification pump 5 and pipelines can be used to drain the water from the internal refueling water tank 1 to the reactor pit injection tank 42. After the internal refueling water tank 1 is overhauled, the reactor pit injection tank 42 can directly return water to the internal refueling water tank 1 via the bottom pipeline by gravity.

[0071] like Figure 9 As shown, in some embodiments, in step S2, discharging the water in the internal refueling water tank 1 to the loading well 43 includes: discharging the water in the internal refueling water tank 1 through the pipeline of the reactor water pool and the fuel water pool cooling and treatment system (PTR) (reference Figure 9 The green solid line pipeline in the middle) is discharged to the loading well 43. Specifically, under normal circumstances, the purification pump 5 of the PTR has a protection mechanism, which means that when the liquid level of the internal replacement water tank 1 is lower than 0.5m, the purification pump 5 of the PTR will stop operating. During the overhaul of the unit, the loading well 43 is in an empty standby state, which can provide about 330m 3 Without any physical equipment modifications, the protection logic of the PTR's purge pump 5 can be modified to ensure continuous operation during the internal refueling water tank 1 emptying mode. This allows the PTR's purge pump 5 to be used as a power source to drain the water in the internal refueling water tank 1 through the PTR's pipeline to the loading well 43. Similarly, after the internal refueling water tank 1 is overhauled, the purge pump 5 can be used to provide reverse power to return the water in the loading well 43 to the internal refueling water tank 1.

[0072] Specifically, if Figure 8 and Figure 9 As shown, the pipeline valve assembly of the PTR system also includes a fifth pipeline 88, a sixth pipeline 89 and a seventh pipeline 90. One end of the fifth pipeline 88 is connected to the third pipeline 83, and the other end is connected to the reactor pit water injection tank 42 or placed above the opening of the reactor pit water injection tank 42. The water in the internal refueling water tank 1 is discharged to the reactor pit water injection tank 42 through the first pipeline 81, the second pipeline 82, the third pipeline 83 and the fifth pipeline 88 in sequence. Figure 1 and Figure 2As shown, the pit injection tank 42 and the internal refueling water tank 1 are connected via an eighth pipe 91. After the internal refueling water tank 1 is overhauled, the water in the pit injection tank 42 can be directly returned to the internal refueling water tank 1 via this eighth pipe 91. A sixth pipe 89 has one end connected to the third pipe 83 and the other end connected to the loading well 43 or positioned above the opening of the loading well 43. Furthermore, the interface where the sixth pipe 89 connects to the third pipe 83 is located between the purification unit 87 and the second valve 86. A seventh pipe 90 has one end connected to the bottom of the loading well 43 and the other end connected to the first pipe 81. Water in the internal refueling water tank 1 is discharged to the loading well 43 sequentially through the first pipe 81, the second pipe 82, the third pipe 83, and the sixth pipe 89. After the internal refueling water tank 1 is overhauled, the water in the loading well 43 flows back to the first pipe 81 via the seventh pipe 90, and then returns to the internal refueling water tank 1 through the first pipe 81, the second pipe 82, and the third pipe 83.

[0073] In a nuclear power plant, the nuclear island waste liquid discharge system (TER) is responsible for collecting radioactive waste liquid from various sources within the nuclear island and for safely managing and environmentally friendly discharging the collected radioactive waste liquid. Furthermore, adjacent units share a nuclear island waste liquid discharge system (TER), meaning that the same nuclear island waste liquid discharge system (TER) is connected to at least two different units. Furthermore, when the reactor is in an operating cycle (no refueling required), the loading well 43 can be in low-water-level standby mode. Thus, for a unit undergoing maintenance, the loading well 43 of an adjacent unit in daily operation can serve as a water storage container.

[0074] In some embodiments, the water storage unit further includes a loading well 43 of an adjacent unit of the unit to be overhauled. The adjacent unit is a unit in daily operation (no refueling required). Correspondingly, discharging the water in the internal refueling water tank 1 to the loading well 43 of the adjacent unit of the unit to be overhauled includes: discharging the water in the internal refueling water tank 1 to the loading well 43 of the adjacent unit of the unit to be overhauled through the nuclear island waste liquid discharge system (TER) shared by the adjacent units. For example, Unit 3 of a nuclear power plant is the unit to be overhauled, and the water in the internal refueling water tank 1 of Unit 3 can be discharged to the loading well 43 of Unit 4 through the TER. That is, the loading well 43 of the adjacent unit of the unit to be overhauled can be used as a backup container. When the volume of the coolant storage tank 41, the reactor pit water injection tank 42 and the loading well 43 of the unit to be overhauled is not sufficient to accommodate the water required to be discharged from the internal refueling water tank 1, the loading well 43 of the adjacent unit of the unit to be overhauled can be used to supplement the water storage to improve the flexibility of the water storage unit. Similarly, after the internal refueling water tank 1 is overhauled, the water in the loading well 43 of the adjacent unit can be transferred back to the internal refueling water tank 1 .

[0075] See also Figure 8 and Figure 9The PTR pipeline valve assembly also includes a ninth pipeline 92, one end of which is connected to the third pipeline 83 and the other end is connected to the TER system; and the interface connecting the ninth pipeline 92 and the third pipeline 83 is located between the purification unit 87 and the second valve 86. Figure 10 and Figure 11 ,in Figure 10 It is a schematic diagram of the local piping system of the unit to be overhauled (e.g., Unit 3 mentioned above); Figure 11 Schematic diagram of a local pipeline system of an adjacent unit to be overhauled (e.g., Unit 4 described above). Specifically, in some embodiments, discharging the water in the internal refueling water tank 1 to the loading well 43 of the adjacent unit to be overhauled through the nuclear island waste liquid discharge system shared by the adjacent units includes the following steps:

[0076] S221, please refer to Figure 10 , discharge the water in the internal refueling water tank 1 of the unit to be repaired into the pipeline of the nuclear island waste liquid discharge system (TER), flush the pipeline of the nuclear island waste liquid discharge system, and discharge the flushed water into the water storage tank of the nuclear island waste liquid discharge system; thereby ensuring that there are no impurities along the pipeline. Specifically, this process can use the purification pump 5 of the PTR to provide a power source. Figure 10 The middle blue pipeline is the pipeline from which the water in the internal refueling water tank 1 of the unit to be repaired reaches the PTR system through the RCV system, and then reaches the TER system through the PTR system pipeline. Figure 10 The blue pipeline in Figures 6 to 9 The first pipe 81, the second pipe 82, the third pipe 83 and the ninth pipe 92 in the RCV system are connected. That is, the water in the internal refueling water tank 1 of the unit to be repaired reaches the first pipe 81, the second pipe 82, the third pipe 83 and the ninth pipe 92 of the PTR system through the RCV system, and reaches the TER system through the ninth pipe 92.

[0077] S222, confirm whether the water quality of the internal replacement water tank 1 of the unit to be repaired is qualified, if so, execute step S223; if not, do not execute step S223.

[0078] S223, please refer to Figure 11 After confirming that the water quality of the internal refueling water tank 1 of the unit to be repaired is qualified, the water in the internal refueling water tank 1 of the unit to be repaired is transferred to the loading well 43 of the adjacent unit to be repaired through the pipeline of the nuclear island waste liquid discharge system. Specifically, the nuclear island waste liquid discharge system is connected to the pipeline of the PTR system of each unit, and the pipeline of the PTR system is connected to the loading well 43 of the adjacent unit. Therefore, after the water in the internal refueling water tank 1 of the unit to be repaired is transferred to the nuclear island waste liquid discharge system, Figure 11The medium blue pipeline is then transmitted to the loading well 43 of the adjacent unit through the pipeline of the PTR system of the adjacent unit to be repaired, thereby realizing the cross-unit transmission of boron water. Figure 11 The blue pipeline in Figures 6 to 9 The sixth pipe 89 in.

[0079] It can be understood that the above embodiments only express the preferred implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the patent scope of the present invention. It should be pointed out that for ordinary technicians in this field, without departing from the concept of the present invention, the above technical features can be freely combined, and several deformations and improvements can be made, all of which fall within the scope of protection of the present invention. Therefore, all equivalent changes and modifications made to the scope of the claims of the present invention should fall within the scope of coverage of the claims of the present invention.

Claims

1. A method for inspecting and repairing a reactor cavity pool and its connected primary circuit piping and internal refueling water tank during a reactor overhaul, characterized in that: The following steps are involved: S1. Place the unit to be overhauled in the reactor complete unloading mode; S2. In the reactor complete unloading mode, at least part of the water in the reactor cavity pool (21) and the primary loop pipe (3) connected thereto of the unit to be overhauled is discharged into the internal refueling water tank (1) of the unit to be overhauled, and at the same time, the water in the internal refueling water tank (1) is discharged into a water storage unit, the water storage unit comprising a coolant storage tank (41), a reactor pit water injection tank (42), and a loading well (43) of the unit to be overhauled; S3. After the reactor cavity pool (21), the connected primary loop pipe (3), and the internal refueling water tank (1) are emptied in parallel, the reactor cavity pool (21), the connected primary loop pipe (3), and the internal refueling water tank (1) are inspected and repaired in parallel.

2. The method for inspecting and repairing the reactor cavity pool and its connected primary circuit piping and internal refueling water tank during reactor overhaul according to claim 1, characterized in that: In step S2, discharging at least part of the water in the reactor cavity pool (21) of the unit to be overhauled and the primary loop pipe (3) connected thereto into the internal refueling water tank (1) comprises the following steps: S201, the water in the primary circuit pipe (3) connected to the reactor cavity pool (21) is discharged to the internal refueling water tank (1) through the hot pipe section (62) of the safety injection system; at the same time, the water in the reactor cavity pool (21) is discharged to the internal refueling water tank (1) through the gravity drain line (63) until the reactor cavity pool (21) and the primary circuit connected thereto reach the low water level; S202, after the reactor cavity pool (21) and the first loop connected thereto reach the lowest water level, the water in the transition section of the first loop pipe (3) connected to the reactor cavity pool (21) flows to the nuclear island drainage system through the first loop transition section drainage pipe, and is then pumped to the coolant storage and treatment system through the nuclear island drainage system.

3. The method for inspecting and repairing the reactor cavity pool and its connected primary circuit piping and internal refueling water tank during reactor overhaul according to claim 1, characterized in that: In step S2, discharging the water in the internal displacement water tank (1) to the coolant storage tank (41) includes: discharging the water in the internal displacement water tank (1) to the coolant storage tank (41) through a short circulation pipeline (64) and a low-pressure drain pipeline (61) of a chemical and volume control system.

4. The method for inspecting and repairing the reactor cavity pool and its connected primary circuit piping and internal refueling water tank during reactor overhaul according to claim 1, characterized in that: In step S2, discharging the water in the internal replacement water tank (1) to the coolant storage tank (41) includes the following steps: S211, introducing a new drainage pipeline (65), one end of which is connected to the pipelines of the reactor water pool and the fuel water pool cooling and treatment system, and the other end of which is connected to the coolant storage tank (41); S212, draining the water in the internal replacement water tank (1) to the coolant storage tank (41) through the newly added drainage pipeline (65).

5. The method for inspecting and repairing the reactor cavity pool and its connected primary circuit piping and internal refueling water tank during reactor overhaul according to claim 1, characterized in that: In step S2, the water in the internal replacement water tank (1) is discharged to the coolant storage tank (41), and at the same time, the water in the coolant storage tank (41) flows to the boron recovery system, and the boron recovery system simultaneously performs boron-water separation.

6. The method for inspecting and repairing the reactor cavity pool and its connected primary circuit piping and internal refueling water tank during reactor overhaul according to claim 1, characterized in that: In step S2, discharging the water in the internal refueling water tank (1) to the reactor pit water injection tank (42) includes: discharging the water in the internal refueling water tank (1) to the reactor pit water injection tank (42) through pipelines of the reactor water pool and fuel water pool cooling and treatment system.

7. The method for inspecting and repairing the reactor cavity pool and its connected primary circuit piping and internal refueling water tank during reactor overhaul according to claim 1, characterized in that: In step S2, discharging the water in the internal refueling water tank (1) to the loading well (43) includes: discharging the water in the internal refueling water tank (1) to the loading well (43) through pipelines of the reactor water pool and fuel water pool cooling and treatment system.

8. The method for inspecting and repairing the reactor cavity pool and its connected primary circuit piping and internal refueling water tank during reactor overhaul according to claim 1, characterized in that: The water storage unit further comprises a loading well (43) of an adjacent unit of the unit to be repaired.

9. The method for inspecting and repairing the reactor cavity pool and its connected primary circuit piping and internal refueling water tank during reactor overhaul according to claim 8, characterized in that: Discharging the water in the internal refueling water tank (1) to the loading well (43) of the adjacent unit of the unit to be overhauled comprises: discharging the water in the internal refueling water tank (1) to the loading well (43) of the adjacent unit of the unit to be overhauled through the nuclear island waste liquid discharge system shared by the adjacent units.

10. The method for inspecting and repairing the reactor cavity pool and its connected primary circuit piping and internal refueling water tank during reactor overhaul according to claim 9, characterized in that: Discharging the water in the internal refueling water tank (1) to the loading well (43) of the adjacent unit of the unit to be overhauled through the nuclear island waste liquid discharge system shared by the adjacent units comprises the following steps: S221, discharging the water in the internal refueling water tank (1) of the unit to be overhauled into the pipeline of the nuclear island waste liquid discharge system, flushing the pipeline of the nuclear island waste liquid discharge system, and discharging the flushed water into the water storage tank of the nuclear island waste liquid discharge system; S222, confirm whether the water quality of the internal replacement water tank (1) of the unit to be repaired is qualified, if so, execute step S223; S223, the water in the internal refueling water tank (1) of the unit to be overhauled is transferred to the loading well (43) of the adjacent unit to be overhauled through the pipeline of the nuclear island waste liquid discharge system.

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