Evaluation method, evaluation device, and program

Abstract

This provides a method for evaluating environmental conditions after a LOCA (Local Occurrence of a Computational Accident) occurs. [Solution] The evaluation method is a method for evaluating the environmental conditions inside a reactor containment vessel, and includes the step of calculating the steam flow rate generated from the reactor core using a calculation formula that reflects the effect of cooling the core by injecting water into the high-temperature side piping connecting the reactor vessel and the steam generator after a LOCA occurs in a pressurized water reactor, wherein in the calculation step, the water injection flow rate into the high-temperature side piping is set to zero until a predetermined time has elapsed since the occurrence of the LOCA, and after the predetermined time has elapsed, an assumed value is set for the water injection flow rate into the high-temperature side piping.

Description

[Technical Field]

[0001] This disclosure relates to evaluation methods, evaluation apparatus, and programs. [Background technology]

[0002] Figure 1 shows a schematic diagram of the reactor containment vessel 1 of a PWR (Pressurized Water Reactor). The reactor containment vessel 1 comprises the reactor vessel 2, the primary cooling system loop 4, and a steam generator 9, etc. The reactor vessel 2 contains the core 3 loaded with numerous fuel assemblies. The reactor vessel 2 is filled with primary coolant. The primary coolant is supplied by the primary cooling system loop 4. The primary cooling system loop 4 circulates the primary coolant between the reactor vessel 2 and the steam generator 9. The primary cooling system loop 4 comprises a high-temperature side pipe 4a and a low-temperature side pipe 4b, and these pipes are connected to the reactor vessel 2. The two-phase flow of primary coolant and steam heated in the core 3 is supplied to the steam generator 9 via the high-temperature side pipe 4a. The steam generator 9 heats the secondary coolant and generates steam by exchanging heat between the primary coolant and secondary coolant circulating in a secondary system (not shown). The steam generated by the steam generator 9 is supplied to the secondary turbine. The primary coolant, which has exchanged heat with the secondary coolant, is deheated and returned to the reactor vessel 2 via the low-temperature piping 4b. At the bottom of the reactor containment vessel 1 is a pit called the containment vessel recirculation sump or IRWSP5 (In-containment Refueling Water Storage Pit). Water is stored in the containment vessel recirculation sump or IRWSP5 in the event of an accident requiring core cooling.

[0003] If a Loss of Coolant Accident (LOCA) occurs due to damage to piping in the primary cooling system loop 4, causing primary coolant to leak out, the emergency cooling system activates and water is injected into the reactor vessel 2. For example, if one of the multiple (e.g., three) cryogenic side pipes 4b is damaged, primary coolant will leak out of the system as a ruptured flow from the damaged area (arrow 6). The leaked ruptured flow is received by the containment vessel recirculation sump or IRWSP5. Also, if a LOCA occurs, water stored in the RWSP (Refueling Water Storage Pit, located outside the reactor containment vessel 1) or IRWSP5 (not shown) is drawn into the reactor vessel 2 by a safety injection pump (not shown). In the case of existing pressurized water reactors, the water source can be switched to the containment vessel recirculation sump or IRWSP5 before the RWSP water source is depleted. For example, Direct Vessel Injection (DVI) is performed to inject water into the reactor core 3. DVI is a method of cooling the reactor core 3 by directly injecting cooling water into the reactor vessel 2 (arrow 7). In addition, Hot Leg Switch over (HLSO) is performed after a predetermined time has elapsed since the occurrence of LOCA. HLSO is a method of injecting water from the hot leg piping 4a (arrow 8). Originally, HLSO is a measure performed to suppress the precipitation of boric acid in the reactor core 3, but by injecting water from the containment vessel recirculation sump or IRWSP5 directly from the top of the reactor core 3 through HLSO, it is expected to have the effect of cooling the inside of the reactor core 3.

[0004] Patent Document 1 discloses a method for evaluating environmental conditions after a LOCA (Lower-of-Corruption) event using an analysis code. Conventional analysis codes evaluate environmental conditions at the time of a LOCA event without considering the cooling effect of HLSO (High-Level Cooling Operation) on the core 3. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2005-24280 [Overview of the project] [Problems that the invention aims to solve]

[0006] A method is needed to evaluate the environmental conditions inside the reactor containment vessel after a LOCA (Lower-of-Corruption Accident) occurs, taking into account the effects of implementing HLSO (High-Level Nuclear Situation).

[0007] This disclosure provides an evaluation method, an evaluation apparatus, and a program that can solve the above-mentioned problems. [Means for solving the problem]

[0008] The evaluation method of this disclosure is a computer-based method for evaluating environmental conditions inside a reactor containment vessel, comprising the step of calculating the steam flow rate generated from the reactor core using a calculation formula that reflects the effect of cooling the core by injecting water into the high-temperature side piping connecting the reactor vessel and the steam generator after a LOCA occurs in a pressurized water reactor, wherein in the calculation step, the water injection flow rate into the high-temperature side piping is set to zero until a predetermined time has elapsed since the occurrence of the LOCA, and after the predetermined time has elapsed, an assumed value is set for the water injection flow rate into the high-temperature side piping.

[0009] The evaluation apparatus of this disclosure has means for calculating the steam flow rate generated from the reactor core using a calculation formula that reflects the effect of cooling the core by injecting water into the high-temperature side piping connecting the reactor vessel and the steam generator after a LOCA occurs in a pressurized water reactor, and the means for calculating the steam flow rate generated from the reactor core using a calculation formula that reflects the effect of cooling the core by injecting water into the high-temperature side piping connecting the reactor vessel and the steam generator after a LOCA occurs in a pressurized water reactor, wherein the means for calculating sets the water injection flow rate into the high-temperature side piping to zero until a predetermined time has elapsed from the time the LOCA occurs, and sets an assumed value for the water injection flow rate into the high-temperature side piping after the predetermined time has elapsed.

[0010] In addition, the program of the present disclosure is a process for evaluating environmental conditions inside a reactor containment vessel, and includes a step of calculating the steam flow rate generated from the reactor core by a calculation formula reflecting the effect of cooling the reactor core by injecting water into the high-temperature side piping connecting the reactor vessel and the steam generator after a LOCA occurs in a pressurized water reactor. In the step of calculating, the injection flow rate of water into the high-temperature side piping is set to zero until a predetermined time elapses from the occurrence of the LOCA, and after the predetermined time elapses, the computer is caused to execute a process of setting an assumed value for the injection flow rate of water into the high-temperature side piping.

Advantages of the Invention

[0011] According to the evaluation method, evaluation device, and program of the present disclosure, the effect of implementing HLSO can be incorporated to evaluate the environmental conditions during LOCA.

Brief Description of the Drawings

[0012] [Figure 1] It is a schematic diagram of a reactor containment vessel. [Figure 2] It is a block diagram showing an example of an evaluation device according to an embodiment. [Figure 3] It is a diagram showing a method of considering the effect of implementing HLSO according to an embodiment. [Figure 4] It is a flowchart showing an example of environmental condition evaluation processing according to an embodiment. [Figure 5] It is a diagram showing an example of the effect of environmental condition evaluation processing according to an embodiment. [Figure 6] It is a diagram showing an example of the hardware configuration of the evaluation device according to an embodiment.

Modes for Carrying Out the Invention

[0013] <Embodiment> Hereinafter, a method for evaluating environmental conditions during LOCA of the present disclosure will be described with reference to FIGS. 1 to 6. (Configuration) Figure 1 is a schematic diagram of the reactor containment vessel 1. As already explained, when a LOCA (Design Basis Accident) occurs in a pressurized water reactor, DVI (Direct Injection of Water) and HLSO (High-Temperature Injection of Water) are performed, with DVI being injected directly into the reactor vessel 2 and HLSO being injected from the high-temperature side piping 4a. DVI is performed immediately after the LOCA occurs, and HLSO is performed after a predetermined time has elapsed since the LOCA occurred. DVI is performed continuously along with HLSO. Note that DVI may be performed as injection into the low-temperature side piping depending on the type of pressurized water reactor.

[0014] Figure 2 is a block diagram showing an example of an evaluation apparatus according to the embodiment. The evaluation device 10 evaluates the environmental conditions during LOCA using an analysis code. The evaluation device 10 comprises an input receiving unit 11, an evaluation unit 12, and a storage unit 13.

[0015] The input receiving unit 11 receives information and instructions entered using input devices such as keyboards, mice, touch panels, and buttons. For example, the input receiving unit 11 receives input of information necessary for evaluating the environmental conditions inside the reactor containment vessel 1. The input receiving unit 11 records the received information in the storage unit 13 or outputs it to the evaluation unit 12.

[0016] The evaluation unit 12 uses the analysis code 131 stored in the memory unit 13 to evaluate the environmental conditions inside the reactor containment vessel 1. For example, the analysis code 131 simulates the behavior of the liquid phase, droplet phase, and vapor phase inside the reactor containment vessel 1 and performs a long-term release mass and energy evaluation after a LOCA occurs. For example, the analysis code 131 analyzes the behavior of primary cooling water leaking from the primary cooling system loop 4, being injected into the core 3 via IRWSP 5 by DVI or HLSO, the injected water being heated in the core 3 to become steam, the heat being removed by the steam generator 9, and returning to the reactor vessel 2, as well as the associated temporal changes in temperature, pressure, etc., inside the reactor containment vessel 1. In doing so, the analysis code 131 analyzes the temporal changes in temperature, etc., inside the reactor containment vessel 1, taking into account the cooling effect of HLSO on the core 3. The evaluation unit 12 outputs the analysis results to a display device or electronic file.

[0017] The storage unit 13 stores various setting information, processing data during calculations, etc. The storage unit 13 stores an analysis code 131. The analysis code 131 is, for example, a thermal-hydraulic analysis code (computer program) that calculates the thermal-hydraulic behavior in the reactor containment vessel 1.

[0018] FIG. 3 shows a method of reflecting the implementation effect of HLSO in the evaluation of environmental conditions. The environmental conditions are the ambient temperature, pressure, etc. inside the reactor containment vessel 1. Hereinafter, the ambient temperature inside the reactor containment vessel 1 will be described. For the evaluation of the ambient temperature inside the reactor containment vessel 1, the analysis code 131 calculates the steam flow rate generated from the core 3. Table 1 shows the calculation method of the steam flow rate generated from the core 3. Item No. 1 in Table 1 shows the conventional method for evaluating the steam flow rate. Specifically, the steam flow rate after the occurrence of LOCA is evaluated by Equation (1) in FIG. 3. The left side (m · stream ) of Equation (1) is the steam flow rate per unit time generated from the core 3. Q on the right side of Equation (1) · Decay represents the decay heat of the core per unit time, and Q · The heat quantity per unit time released from the heat quantities held in the primary system and the secondary system is shown. H in the denominator on the right side of Equation (1) · Decay represents the decay heat of the core per unit time, and Q · Release is the heat quantity per unit time released from the heat quantities held in the primary system and the secondary system. H on the right side of Equation (1) StreamSat represents the saturated steam enthalpy inside the reactor containment vessel 1, and H Liq represents the largest of the saturated enthalpy at the vapor partial pressure inside the reactor containment vessel 1, the enthalpy of the liquid phase of the containment vessel recirculation sample or IRWSP5, and the enthalpy of the liquid phase of the reactor vessel 2. Each enthalpy is a value corresponding to the internal pressure of the reactor containment vessel 1 at each moment (the same applies to H LiqIRWSP , H LiqRVSat ). Equation (1) is an equation showing how much steam is generated per unit time from water by the given heat quantity. In the conventional analysis code, the steam flow rate generated from the core 3 after the occurrence of LOCA is calculated by Equation (1), and the ambient temperature inside the reactor containment vessel 1 is calculated based on this steam flow rate.

[0019] In contrast, in this embodiment, the long-term environmental conditions inside the reactor containment vessel 1 after a LOCA occur are mitigated by considering the effect of HLSO. Specifically, as shown in item 2 of Table 1, analysis code 131 evaluates the steam flow rate using equation (1) as in the conventional method before HLSO is performed (until 24 hours have elapsed since the LOCA occurred), and evaluates the steam flow rate using equation (2) in Figure 3 after HLSO is performed (after a predetermined time has elapsed since the LOCA occurred). The denominator of equation (2) is the same as that of equation (1), and a term for sensible heat cooling by HLSO is added to the numerator. · HLInjection H indicates the injection flow rate of water injected from the high-temperature side pipe 4a. LiqRVSat H is the saturated enthalpy of the liquid phase in reactor vessel 2, LiqIRWSP This is the enthalpy of the water injected from IRWSP5 into the high-temperature side piping 4a by HLSO. The sensible heat cooling term means that the water injected by HLSO cools the core 3 until it boils, and is a term intended to reflect the effect of HLSO in suppressing the amount of steam generated in the core.

[0020] Regarding item 2 in Table 1, to put it another way, in this embodiment, the steam flow rate generated from the reactor core 3 is calculated using equation (2). In this case, until a predetermined time has elapsed since the occurrence of LOCA, the injection flow rate of water injected from the high-temperature side piping 4a is set to zero. After the predetermined time has elapsed, an assumed value is set for the injection flow rate of water into the high-temperature side piping 4a, and the steam flow rate is calculated. According to equation (2), the steam flow rate is evaluated more conservatively compared to equation (1), and consequently, the temperature inside the reactor containment vessel 1 after the occurrence of LOCA is also evaluated to be lower. Therefore, the long-term environmental conditions inside the reactor containment vessel 1 during LOCA can be mitigated.

[0021] Furthermore, the validity of equation (2) has been confirmed through theoretical calculations and experiments that (a) after a predetermined time has elapsed since the occurrence of LOCA, the water injected by HLSO flows into the reactor vessel 2 without being entrained by the two-phase counterflow, and (b) the injected water that flows into the core 3 is mixed. In addition, the timing of HLSO is currently, for example, 24 hours after the occurrence of LOCA, but it is not limited to this. When evaluating the steam flow rate generated from the core 3 while considering the effect of HLSO, it is possible to switch from equation (1) to equation (2) to match the timing of when HLSO is actually implemented.

[0022] (operation) Next, the operation of the evaluation device 10 will be explained using Figure 4. Figure 4 is a flowchart showing an example of the environmental condition evaluation process according to the embodiment. First, the user sets the information necessary for evaluating environmental conditions in the evaluation device 10, such as the structure of the reactor containment vessel 1, the configuration and thermal output of the reactor core 3, the water temperature and volume of the IRWSP5, the location of piping damage, and the evaluation period (e.g., several months after the occurrence of LOCA), and instructs the device to perform the environmental condition evaluation. The input reception unit 11 receives the input information and the instruction to perform the environmental condition evaluation. Then, the evaluation unit 12 starts evaluating the environmental conditions inside the reactor containment vessel 1 after the occurrence of LOCA using the analysis code 131 (step S1). The analysis code 131 simulates the behavior of various fluids inside the reactor containment vessel 1 and analyzes the temporal changes in temperature, pressure, etc., at various locations. At this time, the analysis code 131 calculates the steam flow rate generated from the reactor core 3. Until a predetermined time (e.g., 24 hours) has elapsed since the occurrence of LOCA (step S2; No), the analysis code 131 calculates the steam flow rate using equation (1) in Figure 3 (step S3). Q in equation (1) · Decay Q · Release H StreamSat H Liq The moment-by-moment values ​​analyzed by analysis code 131 are substituted into this. Once a predetermined time has elapsed since LOCA occurred (step S2; Yes), analysis code 131 calculates the steam flow rate using equation (2) in Figure 3 (step S4). Q in equation (2)· Decay Q · Release H StreamSat H LiqRVSat H LiqIRWSP H Liq The moment-by-moment values ​​analyzed by analysis code 131 are substituted into this. The m in equation (2) · HLInjection A predetermined assumed value is substituted into this value. The analysis code 131 also calculates the ambient temperature inside the reactor containment vessel 1 based on the calculated steam flow rate and a predetermined calculation formula. The evaluation unit 12 records the moment-by-moment steam flow rate and ambient temperature calculated by the analysis code 131 in the storage unit 13. Next, the evaluation unit 12 determines whether the analysis for the evaluation period has been completed. If it has not been completed (step S5; No), it repeats the process from step S2. If the analysis for the evaluation period has been completed (step S5; Yes), the evaluation unit 12 completes the evaluation of the environmental conditions inside the reactor containment vessel 1 after the LOCA occurrence using the analysis code 131. Next, the evaluation unit 12 outputs the evaluation results (step S6) and completes the environmental condition evaluation process shown in Figure 4.

[0023] Figure 5 shows an example of the analysis results. Figure 5 is a diagram showing an example of the effect of the environmental condition evaluation process according to the embodiment. The vertical axis of Figure 5 shows the ambient temperature inside the reactor containment vessel 1 (CV), and the horizontal axis shows the elapsed time after the occurrence of LOCA, expressed logarithmically. Graph 51 shows the change in ambient temperature inside the reactor containment vessel 1 calculated by analysis code 131. Graph 51 branches into graphs 51a and 51b after 24 hours have elapsed since the occurrence of LOCA. Graph 51a shows the ambient temperature calculated by the flowchart process in Figure 4. Graph 51b shows the ambient temperature when the steam flow rate is calculated using equation (1) in Figure 3 even after 24 hours have elapsed since the occurrence of LOCA. As shown, graph 51a yields a lower result than graph 51b.

[0024] (effect) As described above, according to this embodiment, the environmental conditions after a LOCA (Lower-of-Corruption Accident) can be evaluated while taking into account the effects of implementing HLSO (effect of suppressing core-generated steam).

[0025] Figure 6 shows an example of the hardware configuration of the evaluation device. The computer 900 includes a CPU 901, main memory 902, auxiliary memory 903, input / output interface 904, and communication interface 905. The evaluation device 10 described above is implemented in the computer 900. The functions described above are stored in auxiliary storage device 903 in the form of a program. The CPU 901 reads the program from auxiliary storage device 903, loads it into main memory 902, and executes the above processing according to the program. The CPU 901 also allocates storage space in main memory 902 according to the program. The CPU 901 also allocates storage space in auxiliary storage device 903 to store the data being processed according to the program.

[0026] Furthermore, a program to implement all or part of the functions of the evaluation device 10 may be recorded on a computer-readable recording medium, and the program recorded on this recording medium may be loaded into a computer system and executed to perform processing by each functional unit. Here, "computer system" includes hardware such as the OS and peripheral devices. Also, if a WWW system is used, "computer system" also includes the homepage provisioning environment (or display environment). Furthermore, "computer-readable recording medium" refers to portable media such as CDs, DVDs, USBs, and storage devices such as hard disks built into the computer system. In addition, if this program is distributed to computer 900 via a communication line, computer 900 that receives the program may load it into main memory 902 and execute the above processing. Furthermore, the above program may be for implementing part of the functions described above, and may also be for implementing the above functions in combination with programs already recorded in the computer system.

[0027] As described above, several embodiments relating to this disclosure have been explained, but all of these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be carried out in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents.

[0028] <Note> The evaluation method, evaluation apparatus, and program described in the embodiment can be understood, for example, as follows.

[0029] (1) The evaluation method according to the first embodiment is a method for evaluating environmental conditions inside a reactor containment vessel, performed by a computer, and comprises the step of calculating the steam flow rate generated from the reactor core by a calculation formula that reflects the effect of cooling the core by injecting water into the high-temperature side piping connecting the reactor vessel and the steam generator after a LOCA occurs in a pressurized water reactor, wherein in the calculation step, the water injection flow rate into the high-temperature side piping is set to zero until a predetermined time has elapsed since the occurrence of the LOCA, and after the predetermined time has elapsed, an assumed value is set for the water injection flow rate into the high-temperature side piping. This allows us to incorporate the effects of HLSO implementation and evaluate the environmental conditions during LOCA.

[0030] (2) The evaluation method relating to the second aspect is the evaluation method of (1), wherein the calculation formula is H Liq When the enthalpy of saturated water at the partial pressure of vapor in the reactor containment vessel 1, the enthalpy of water injected into the high-temperature side piping, and the enthalpy of the liquid phase of the reactor vessel are taken as the largest of these, the following formula holds: Steam flow rate from the core = {(Core decay heat + Heat released from the heat amount held by the pressurized water reactor) - Flow rate of water injected into the high-temperature side piping × (Enthalpy of the liquid phase of the reactor vessel - Enthalpy of water injected into the high-temperature side piping)} ÷ (Enthalpy of saturated vapor in the reactor containment vessel - H Liq ). This allows for the calculation of steam flow rates generated from the reactor core, taking into account the effects of HLSO.

[0031] (3) The evaluation method relating to the third aspect is the evaluation method of (1) to (2), wherein the predetermined time is 24 hours.

[0032] (4) The evaluation apparatus according to the fourth embodiment has means for calculating the steam flow rate generated from the reactor core using a calculation formula that reflects the effect of cooling the core by injecting water into the high-temperature side piping connecting the reactor vessel and the steam generator after a LOCA occurs in a pressurized water reactor, wherein the means for calculating sets the water injection flow rate into the high-temperature side piping to zero until a predetermined time has elapsed from the time the LOCA occurs, and sets an assumed value for the water injection flow rate into the high-temperature side piping after the predetermined time has elapsed.

[0033] (5) The program according to the fifth embodiment causes a computer to perform a process for evaluating the environmental conditions inside the reactor containment vessel, which includes a step of calculating the steam flow rate generated from the reactor core using a calculation formula that reflects the effect of cooling the core by injecting water into the high-temperature side piping connecting the reactor vessel and the steam generator after a LOCA occurs in a pressurized water reactor, wherein in the calculation step, the water injection flow rate into the high-temperature side piping is set to zero until a predetermined time has elapsed since the occurrence of the LOCA, and after the predetermined time has elapsed, an assumed value is set for the water injection flow rate into the high-temperature side piping. [Explanation of Symbols]

[0034] 1. Reactor containment vessel 2...Reactor vessel 3. Core 4. Primary cooling system loop 5···IRWSP 9. Steam generator 10. Evaluation device 11. Input Reception Section 12. Evaluation Department 13...Storage section 131... Analysis code 900... Computer 901···CPU 902...Main memory 903...Auxiliary storage device 904... Input / Output Interface 905...Communication Interface

Claims

1. A method for evaluating environmental conditions inside a reactor containment vessel, performed by a computer, A step in calculating the steam flow rate generated from a pressurized water reactor using a formula that reflects the effect of cooling the core by injecting water into the high-temperature side piping connecting the reactor vessel and the steam generator after a Loss of Coolant Accident (LOCA) occurs in the pressurized water reactor. It has, In the calculation step described above, Until a predetermined time has elapsed since the occurrence of the aforementioned LOCA, the water injection flow rate into the high-temperature side piping shall be set to zero. After the predetermined time has elapsed, set an assumed value for the water injection flow rate into the high-temperature side piping. Evaluation method.

2. The above calculation formula is H Ｌｉｑ When the enthalpy of saturated water at the partial pressure of vapor inside the reactor containment vessel 1, the enthalpy of water injected into the high-temperature side piping, and the enthalpy of the liquid phase of the reactor vessel are taken as the largest of these, the following equation holds: Steam flow rate from the reactor core = {(Core decay heat + Heat released from the heat contained in the pressurized water reactor) - Water injection flow rate into the high-temperature side piping × (Enthalpy of the liquid phase of the reactor vessel - Enthalpy of the water injected into the high-temperature side piping)} ÷ (Saturated steam enthalpy of the reactor containment vessel - H Ｌｉｑ ) The evaluation method according to claim 1.

3. The aforementioned predetermined time is 24 hours. The evaluation method according to claim 1 or claim 2.

4. Regarding the environmental conditions inside the reactor containment vessel after a Loss of Coolant Accident (LOCA) occurs in a pressurized water reactor, A means for calculating the steam flow rate generated from a pressurized water reactor after a LOCA (Low-Level Cooling Amount) occurs, using a calculation formula that reflects the effect of cooling the core by injecting water into the high-temperature side piping connecting the reactor vessel and the steam generator. It has, The means for performing the calculation is, Until a predetermined time has elapsed from the time the aforementioned LOCA occurs, the water injection flow rate into the high-temperature side piping shall be set to zero. After the predetermined time has elapsed, set an assumed value for the water injection flow rate into the high-temperature side piping. Evaluation device.

5. A process for evaluating the environmental conditions inside the reactor containment vessel, A step in calculating the steam flow rate generated from a pressurized water reactor using a formula that reflects the effect of cooling the core by injecting water into the high-temperature side piping connecting the reactor vessel and the steam generator after a Loss of Coolant Accident (LOCA) occurs in the pressurized water reactor. It has, In the calculation step described above, Until a predetermined time has elapsed since the occurrence of the aforementioned LOCA, the water injection flow rate into the high-temperature side piping shall be set to zero. After the predetermined time has elapsed, a process is performed to set an assumed value for the water injection flow rate into the high-temperature side piping. A program that causes a computer to execute something.

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