Staged hot functional test method

Abstract

The present invention discloses a staged hot functional test method, comprising the following steps: S1, before the water intake and the drain are connected to the open sea, a commissioning test is performed with the main steam isolation valve of the VVP system closed, the CRF system shut down, and the SEC system taking temporary temperature control measures to ensure safe operation; the temporary temperature control measures taken by the SEC system include: connecting the PX pump room forebay and the GH hot water return ditch to establish a SEC closed circulation loop; operating the SEC closed circulation loop to allow the water in the PX pump room forebay to circulate within the SEC closed circulation loop; S2, after the water intake and the drain are connected to the open sea, relevant tests for opening the main steam isolation valve of the VVP system and some BAS tests and conventional island tests that require the cooperation of the CRF system are performed. The staged hot functional test method of the present invention divides the hot functional test into two stages and performs them step by step to ensure the early start of the hot test and the integrity and effectiveness of the hot test items.

Description

Technical Field

[0001] The present invention relates to the technical field of nuclear power plant commissioning, and in particular to a staged hot function test method. Background Art

[0002] A pressurized water reactor (PWR) nuclear power plant primarily consists of three parts: the pressurized water reactor (PWR), the primary system, and the secondary system. The PWR and primary system primarily constitute the nuclear island, while the secondary system forms the conventional island. The PWR uses low-enriched uranium as fuel and light water as coolant and moderator. This reaction with neutrons produces nuclear fission, releasing heat. This heat is carried out of the reactor by high-pressure water flowing through the primary system, where it is transferred to the secondary water in the steam generator. The heated secondary water generates steam that drives the steam turbine, which in turn drives the generator to generate electricity.

[0003] To verify the reliability of nuclear power plant systems and equipment and ensure safe and stable operation after nuclear fuel loading (referred to as fuel loading), a hot functional test (referred to as hot test) is scheduled before fuel loading as a "dress rehearsal" before the reactor is loaded. The reactor and primary circuit system are tested for the first time without nuclear fuel, during the process of increasing temperature and pressure, then decreasing temperature and pressure. These tests aim to: verify the functional response of relevant systems and equipment across the entire pressure and temperature range, from pressure vessel cover closing to hot shutdown; verify unit safe startup; conduct pre-fuel loading trial runs and periodic tests; passivate the reactor coolant system; dynamically balance the reactor coolant pumps; perform relevant hot tests on the primary and secondary circuits; conduct various power outage and gas loss tests; and perform KIC / BUP / RSS switching during unit shutdown.

[0004] Hot testing is an extremely large, high-risk, and highly challenging commissioning project for pressurized water reactor nuclear power units. During the entire hot testing period, the nuclear island system equipment must be in operation throughout, and the corresponding nuclear island terminal cold source SEC system (critical plant water system) must also operate continuously. The RRI system (equipment cooling water system) is used to cool the nuclear island-related system equipment to ensure the safe and stable operation of the unit. In addition, the conventional island system equipment is mainly put into operation in the later stages of the hot testing, involving the opening of the main steam isolation valve of the VVP system (main steam system), some BAS tests (power switching tests), and tests of the conventional island itself. The corresponding CRF system (circulating water system) must also be operated during this period.

[0005] Under normal circumstances, seawater enters the PX (Combined Pump Station) pumphouse forebay through the CA (water intake), where both the SEC and CRF systems draw water. After heat exchange, it flows through the GS (critical plant water drainage corridor) and GD (circulating water inlet and outlet trench) corridors, respectively, to the CC (drain outlet) well. Finally, the CC well is discharged to the open sea. The sea serves as the ultimate heat sink, receiving heat generated by the nuclear island and conventional island system equipment.

[0006] The current standard and common practice for hot trials is to ensure that both the CA and CC are fully connected to the open sea and have normal water supply and discharge conditions before the hot trial begins. This allows the SEC and CRF systems to draw water from the CA via the PX pumphouse forebay. After heat exchange, the water is then discharged to the CC well and ultimately to the sea. This ensures cooling of the nuclear and conventional island systems and equipment throughout the hot trial, ensuring safe operation of the unit. The entire hot trial lasts approximately one month, including the normal uplink and downlink processes of the unit, during which various tests are completed.

[0007] The aforementioned approach requires that the CA and CC be fully connected to the open sea and have normal water intake and discharge conditions before hot testing of nuclear power units. However, with the country's increasing emphasis on the environment and increasingly stringent regulations, nuclear power project construction faces significant challenges and difficulties in sea area use approval. The process is complex, time-consuming, and requires repeated clarifications. The approval of sea area use rights is subject to high uncertainty, often preventing scheduled construction of the CA and CC areas connected to the open sea. Consequently, the CA and CC cannot be connected to the open sea before hot testing begins, preventing hot testing from proceeding in the normal manner. This can have a significant impact on the construction of nuclear power units. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a staged hot function test method.

[0009] The technical solution adopted by the present invention to solve the technical problem is to provide a staged hot function test method, including the following steps:

[0010] S1. Before the water intake and outlet are connected to the open sea, a commissioning test is performed with the main steam isolation valve of the VVP system closed, the CRF system shut down, and the SEC system taking temporary temperature control measures to ensure safe operation. The commissioning test includes commissioning tests of the nuclear island, instrumentation and control, and electrical systems.

[0011] Among them, the temporary temperature control measures taken by the SEC system include:

[0012] S1.1. Connect the PX pump room forebay and the GH hot water return ditch to establish a SEC closed circulation loop;

[0013] S1.2, operate the SEC closed circulation loop, so that the water in the PX pump room forebay circulates in the SEC closed circulation loop;

[0014] S2. After the water intake and discharge outlet are connected to the open sea, perform the relevant tests of opening the main steam isolation valve of the VVP system and some BAS tests and conventional island tests that require the operation of the CRF system.

[0015] Preferably, in step S1.1, a temporary culvert is set up to connect the PX pump room front pool and the GH hot water return ditch, so that the temporary culvert, PX pump room front pool, SEC system, GS overflow well, GS drainage corridor, CC siphon well, GD circulating water corridor and GH hot water return ditch are connected in sequence to form the SEC closed circulation loop.

[0016] Preferably, in step S1.2, when the SEC closed circulation loop is operated, the SEC pump of the SEC system draws water from the PX pump room forebay and transports the drawn water to the GS overflow well, the GS drainage gallery and the CC siphon well; after the water level in the CC siphon well rises, the water flows under the action of gravity along the GD circulating water gallery to the GH hot water return ditch, and finally returns to the PX pump room forebay through the temporary culvert.

[0017] Preferably, the temporary temperature control measures taken by the SEC system also include:

[0018] S1.3. Set up a pumping device to draw water from the open sea as a cold source and inject it into the SEC closed circulation loop.

[0019] Preferably, step S1.3 is started before the water temperature of the SEC closed circulation loop reaches the design reference temperature of the SEC system or when the water temperature reaches the design reference temperature of the SEC system.

[0020] Preferably, in step S1.3, the CC siphon well is connected to the pumping device as an injection point of the cold source.

[0021] Preferably, in step S1.3, based on the absolute elevation of the entire SEC closed circulation loop, the lower edge of the dual-unit connecting channel of the GS overflow well is taken as the highest water level. When the water level of the entire SEC closed circulation loop exceeds the highest water level, overflow is automatically performed to maintain the balance of the water loading of the entire SEC closed circulation loop.

[0022] Preferably, in step S1.3, the water overflowing from the SEC closed circulation loop is discharged to the rainwater pipe network through a temporary channel.

[0023] Preferably, in step S1.3, the water injection flow rate of the cold source is calculated according to the following formula (1):

[0024]

[0025] Where q is the water injection flow rate; W is the heat load generated during the hot test; ρ is the density of the cold source; c is the specific heat capacity of the cold source; t R is the water temperature at the inlet of the SEC closed loop; t SEA is the water injection temperature.

[0026] Preferably, the pumping device includes a plurality of water injection pumps.

[0027] Preferably, among the multiple water injection pumps, at least one is a main pump and at least one is a backup pump.

[0028] Preferably, the pumping device is provided with two independent power supplies, wherein one power supply is used to supply power to the main pump, and the other power supply is used to supply power to the backup pump.

[0029] The staged hot functional test method of the present invention divides the hot functional test into two stages and performs them step by step, thereby ensuring an early start of the hot test and guaranteeing the integrity and effectiveness of the hot test items. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0031] Figure 1 is a connection block diagram of a SEC closed-loop circuit in a staged hot functional test method according to some embodiments of the present invention;

[0032] Figure 2 is a schematic diagram of the connection of a water injection pump in a staged hot functional test method according to some embodiments of the present invention;

[0033] Figure 3 This is a circuit configuration diagram of a water injection pump in a staged hot functional test method according to some embodiments of the present invention. DETAILED DESCRIPTION

[0034] 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.

[0035] The staged hot functional test method of the present invention divides the hot functional test (hereinafter referred to as hot test) into two stages and performs them step by step. When the CA (water intake) and CC (discharge outlet) are not (or cannot) connected to the open sea, the relevant debugging test of the first stage is carried out first. When the CA and CC are connected to the open sea, the relevant tests of the second stage are carried out.

[0036] refer to Figure 1 The staged hot functional test method of some embodiments of the present invention may include the following steps:

[0037] S1. Before the water intake (CA) and discharge outlet (CC) are connected to the open sea, the commissioning test shall be carried out with the main steam isolation valve of the VVP system (main steam system) closed, the CRF system (circulating water system) shut down, and temporary temperature control measures taken for the SEC system (critical plant water system) to ensure safe operation.

[0038] Among them, the commissioning test includes the commissioning test of nuclear island, instrumentation and control, electrical and other professional tests. The specific operation can refer to the commissioning test in the hot test of the existing technology.

[0039] This step S1 is the first stage and is mainly performed when the CA and CC are not connected to the open sea to ensure the early start of the hot test. The situations where the CA and CC are not connected to the open sea include: delays in offshore construction, etc.

[0040] Among them, the temporary temperature control measures taken by the SEC system include:

[0041] S1.1. Connect the PX pump room forebay 10 and the GH hot water return ditch 20 to establish a SEC closed circulation loop.

[0042] Specifically, a temporary culvert 30 is set between the PX pump room forebay 10 and the GH hot water return ditch 20, and the PX pump room forebay 10 and the GH hot water return ditch 20 are connected through the temporary culvert 30, so that the temporary culvert 30, the PX pump room forebay 10, the SEC system 40, the GS overflow well 50, the GS drainage corridor 60, the CC siphon well 70, the GD circulating water corridor 80 and the GH hot water return ditch 20 are connected in sequence to form a SEC closed circulation loop.

[0043] S1.2. Run the SEC closed circulation loop to allow the water in the PX pump room forebay 10 to circulate in the SEC closed circulation loop.

[0044] During SEC closed-loop operation, the SEC pumps of the SEC system 40 draw water from the PX pumphouse forebay 10 and transport it sequentially through the GS overflow well 50 and the GS drainage gallery 60 to the CC siphon well 70. After the water level in the CC siphon well 70 rises, the water flows under gravity along the GD circulating water gallery 80 to the GH hot water return ditch 20, and finally returns to the PX pumphouse forebay 10 through the temporary culvert 30, completing the water circulation within the SEC closed-loop.

[0045] The above water circulates in the SEC closed circulation loop, and it should be ensured that the water temperature does not exceed the water temperature requirement of the SEC closed circulation loop or the SEC system inlet, such as 27.2℃.

[0046] When the water temperature of the SEC closed circulation loop reaches the design reference temperature of the SEC system, or preferably before the water temperature of the SEC closed circulation loop reaches the design reference temperature of the SEC system, for example 27.2°C, the following step S1.3 is started to draw water from the open sea as a cold source for cooling.

[0047] S1.3. Install a water pumping device to draw water from the open sea as a cold source and inject it into the SEC closed circulation loop.

[0048] Among them, water is taken from the open sea as a cold source and injected into the SEC closed circulation loop, so that the water temperature of the SEC closed circulation loop drops below the design reference temperature of the SEC system. It not only achieves the cooling effect, but also can adaptively adjust the water supply flow rate, which has greater flexibility.

[0049] In order to consider the convenience and economy of on-site arrangement, the injection point of the cold source is selected as the CC siphon well 70 which is closest to the sea. Therefore, the CC siphon well 70 is connected to the pumping device as the injection point of the cold source.

[0050] Combine Figure 1 、 2 The pumping device includes several water injection pumps 100; the number of water injection pumps 100 is determined by the required water injection flow rate and the pump performance parameters of the water injection pumps 100 themselves. In addition, the number of water injection pumps 100 activated can be adjusted based on the actual injection water temperature during actual operation and the water temperature of the SEC closed circulation loop, providing convenient and flexible operation.

[0051] In step S1.3, based on the absolute elevation of the entire SEC closed loop, the lower edge of the dual-unit connecting channel of the GS overflow well 50 is used as the highest water level. When the water level in the entire SEC closed loop exceeds this maximum water level, an automatic overflow is initiated, maintaining a balanced water volume throughout the SEC closed loop and achieving water exchange and temperature control. This automatically overflowed water is discharged through a temporary channel to the stormwater network 90 and ultimately to the open sea.

[0052] Furthermore, water is taken from the open sea as a cold source and injected into the SEC closed circulation loop. The injection flow rate of the cold source is calculated according to the following formula (1):

[0053]

[0054] Where q is the injection flow rate; W is the heat load generated during the hot test, and W is the maximum heat load generated during the hot test. The heat load generated during the hot test is a dynamic variable due to the varying types and quantities of equipment in operation at each stage. To be conservative, the calculation is based on the maximum heat load generated during the hot test. This includes pumps such as SEC, RRI, RRA, RCP, and RCV; heaters such as RCP001-006RS; RRM heat exchangers, DEG / DEL chillers, and DVH heat exchangers.

[0055] ρ is the density of the cold source, that is, the density of the injected water (seawater), for example, it can be 1020 kg / m 3 ,; c is the specific heat capacity of the cold source, that is, the specific heat capacity of the injected water, for example, it can be 4.02kJ / (kg·℃) when it is seawater; t RThe water temperature at the inlet of the SEC closed loop can be determined based on the design reference temperature of the SEC system; t SEA is the injection temperature, that is, the temperature of the injected seawater. When the injected water is fresh water, t SEA Corresponds to the temperature of fresh water.

[0056] Taking the CPR1000 unit as an example, the design reference temperature for normal operation of the SEC system is 27.2°C. At this temperature, the cooling of the nuclear island related system equipment can be effectively guaranteed to meet the hot test requirements. Therefore, t in the above formula (1) is R The corresponding temperature is 27.2℃.

[0057] Specifically, for equation (1) above, the maximum heat load for each stage of the hot test can be estimated by conservatively adding up the rated loads of the relevant system equipment based on the operating requirements of the various system equipment during each stage of the hot test. This conservative calculation is based on the relevant equipment parameters of the nuclear power unit and the maximum number of equipment required to operate at each stage, without considering heat dissipation to the environment. See Table 1 below for details.

[0058] Table 1. Calculation of heat load data at each stage of hot test

[0059]

[0060]

[0061] For the convenience of calculation and to leave enough margin, it is assumed that the heat load during the hot test is a constant value, and the maximum heat load of 35.53MW is used as input.

[0062] Water temperature in SEC closed loop t R , is also a variable in the actual operation process. For the convenience of calculation and from the perspective of economy, it is assumed to be a constant value and input according to the SEC system design reference temperature of 27.2℃.

[0063] Injection water temperature t SEA Seasonal variations are the biggest variable. For example, the approximate timeframe for the hot test of a nuclear power unit in northern Taiwan and the seawater temperature variations in the surrounding waters over the three-year reference period are detailed in Table 2. A conservative 16°C injection temperature was chosen.

[0064] Table 2. Seawater temperature in the sea area where the Northern No. 1 nuclear power unit is located from April to June over the past three years

[0065]

[0066] Combining the above analysis and relevant data input, t R , t SEASubstituting the values ​​of W into formula (1), we get:

[0067]

[0068] The pumping device includes a plurality of water injection pumps 100. The number and type of the water injection pumps 100 are determined according to the water injection flow rate of the required cold source. For example, if the water injection flow rate of the required cold source is 2785m 3 / h, the pumping capacity of each water injection pump 100 can be 950m 3 / h.

[0069] Preferably, the pumping device includes six water injection pumps 100, three of which serve as main pumps and three as standby pumps.

[0070] At the same time, considering the possible changes and adjustments of the water injection flow, the water pipeline is designed as two and several steam traps are set at the low points of the water pipeline to drain the pipeline when the system is shut down to avoid freezing or rust inside the pipeline in cold weather. Figure 2 shown.

[0071] In addition to the 100% redundancy of the mechanical equipment, the pumping system is equipped with two independent power supplies for the water injection pumps 100. Each power supply supplies three water injection pumps 100, fully ensuring the reliability of the water supply. In other words, one power supply powers the three main pumps, and the other power supplies the three backup pumps.

[0072] like Figure 3 As shown, taking the above-mentioned Northern 1 nuclear power unit as an example, the first power supply is taken from the upstream 304# box transformer, and a 400A circuit breaker is taken to supply it locally; the second power supply is taken from the upstream 503# box transformer, and a 400A circuit breaker is taken to supply it locally. Three distribution boxes are set up on site, each containing two 250A circuit breakers. Distribution box 1 is taken from the first power supply, distribution box 2 is taken from the second power supply, and the two circuit breakers in distribution box 3 are connected to the first and second power supplies respectively. Each distribution box supplies power to the local control box of the pump (such as Figure 3 001PO to 006PO control box) shown in the figure. Figure 3 Among them, only two of the three circuit breakers 001JA, 002JA and 003JA can be closed at most, and only two of the three circuit breakers 004JA, 005JA and 006JA can be closed at most.

[0073] The above step S1 serves as the first stage of hot testing, in which the self-circulating operation achieved through the SEC closed loop is combined with offshore water injection cooling to ensure the safe and stable operation of the SEC system and timely remove the heat generated by the nuclear island system equipment during the hot testing.

[0074] This first phase can cover more than 90% of the test items of the hot test.

[0075] It is understandable that the above-mentioned main pumps and backup pumps are not limited to three respectively, and can be increased or decreased according to actual needs so that the corresponding number of main pumps and backup pumps can meet the required water injection flow.

[0076] S2. After the water intake (CA) and the discharge outlet (CC) are connected to the open sea, the remaining operations in the hot functional test can be performed as the second stage of the hot functional test.

[0077] Specifically, this includes: performing tests related to the opening of the VVP system's main steam isolation valve, as well as some BAS tests and conventional island tests that require the operation of the CRF system. It also includes tests that were not performed during the first phase of the hot test or that require revalidation.

[0078] The specific operations performed in the above step S2 may refer to the thermal test procedure operations in the prior art.

[0079] Through the above-mentioned first and second phase hot tests, all test items involved in the hot tests can be completed, and their integrity and effectiveness can be fully guaranteed.

[0080] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention's description and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A staged hot functional test method, characterized in that: The following steps are involved: S1. Before the water intake and outlet are connected to the open sea, a commissioning test is performed with the main steam isolation valve of the VVP system closed, the CRF system shut down, and the SEC system taking temporary temperature control measures to ensure safe operation. The commissioning test includes commissioning tests of the nuclear island, instrumentation and control, and electrical systems. Step S1 is the first stage and is carried out when the water intake and outlet are not connected to the open sea to ensure the early start of the hot test. The temporary temperature control measures taken by the SEC system include: S1.

1. Connect the PX pump room forebay and the GH hot water return ditch to establish a SEC closed circulation loop; Wherein, a temporary culvert is set to connect the PX pump house forebay and the GH hot water return ditch, so that the temporary culvert, PX pump house forebay, SEC system, GS overflow well, GS drainage gallery, CC siphon well, GD circulating water gallery and GH hot water return ditch are connected in sequence to form the SEC closed circulation loop; S1.2, operate the SEC closed circulation loop, so that the water in the PX pump room forebay circulates in the SEC closed circulation loop; S2. After the water intake and discharge outlet are connected to the open sea, perform the relevant tests of opening the main steam isolation valve of the VVP system and some BAS tests and conventional island tests that require the operation of the CRF system.

2. The staged hot functional test method according to claim 1, characterized in that: In step S1.2, when the SEC closed circulation loop is running, the SEC pump of the SEC system draws water from the PX pump room forebay and transports the drawn water to the GS overflow well, the GS drainage corridor and the CC siphon well; after the water level in the CC siphon well rises, the water flows along the GD circulating water corridor to the GH hot water return ditch under the action of gravity, and finally returns to the PX pump room forebay through the temporary culvert.

3. The staged hot functional test method according to claim 1, characterized in that: The temporary temperature control measures taken by the SEC system also include: S1.

3. Set up a pumping device to draw water from the open sea as a cold source and inject it into the SEC closed circulation loop.

4. The staged hot functional test method according to claim 3, characterized in that: Before the water temperature of the SEC closed circulation loop reaches the design reference temperature of the SEC system or when it reaches the design reference temperature of the SEC system, step S1.3 is started.

5. The staged hot function test method according to claim 3, characterized in that: In step S1.3, the CC siphon well is connected to the pumping device as an injection point of the cold source.

6. The staged hot function test method according to claim 3, characterized in that: In step S1.3, based on the absolute elevation of the entire SEC closed circulation loop, the lower edge of the dual-unit connecting channel of the GS overflow well is used as the highest water level. When the water level of the entire SEC closed circulation loop exceeds this highest water level, it will automatically overflow to maintain the balance of the water loading of the entire SEC closed circulation loop.

7. The staged hot function test method according to claim 6, characterized in that: In step S1.3, the overflow water from the SEC closed circulation loop is discharged to the rainwater pipe network through a temporary channel.

8. The staged hot function test method according to claim 5, characterized in that: In step S1.3, the water injection flow rate of the cold source is calculated according to the following formula (1): (one) in, is the water injection flow rate; is the heat load generated during the hot test; is the density of the cold source; is the specific heat capacity of the cooling source; The water temperature at the inlet of the SEC closed loop; is the water injection temperature.

9. The staged hot function test method according to claim 3, characterized in that: The pumping device includes a plurality of water injection pumps.

10. The staged hot function test method according to claim 9, characterized in that: Among the multiple water injection pumps, at least one is a main pump and at least one is a backup pump.

11. The staged hot function test method according to claim 10, characterized in that: The pumping device is provided with two independent power supplies, one of which supplies power to the main pump and the other supplies power to the standby pump.

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