Boron concentration determination device, method, and program

Abstract

To suppress complication and cost increase of a device by easily detecting an abnormality due to the fluctuation of boron concentration in a boron concentration determination device and method, and a program.SOLUTION: A boron concentration determination device comprises: a pure water supply line which supplies pure water; a boric acid solution supply line which supplies a boric acid solution; a boric acid mixture supply line which supplies a boric acid mixture in which the pure water supplied from the pure water supply line is mixed with the boric acid solution supplied from the boric acid solution supply line to reactor cooling water; a first flow meter and a second flow meter which measure the flow rates of at least two lines of the pure water supply line, the boric acid solution supply line and the boric acid mixture supply line; and a determination unit which determines an abnormality due to reduction in the boron concentration in the reactor cooling water on the basis of the actual flow rate ratio of the first flow rate measured by the first flow meter to the second flow rate measured by the second flow meter.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a boron concentration determination device, a boron concentration determination method, and a program. [Background technology]

[0002] For example, a nuclear power plant having a pressurized water reactor (PWR) uses light water as a reactor coolant and neutron moderator, converting it into high-temperature, high-pressure water that does not boil throughout the reactor core, sending the high-temperature, high-pressure water to a steam generator to generate steam through heat exchange, and sending the steam to a turbine generator to generate electricity.

[0003] In pressurized water reactors, reactivity can be controlled by control rod operation or chemical volumetric control (adjusting the boron concentration). The power output of a pressurized water reactor is controlled by control rod operation after maintaining the boron concentration of the cooling water (light water) at a predetermined value by chemical volumetric control. Examples of such reactor control include those described in the following patent documents. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 60-146187 [Patent Document 2] Patent No. 2734483 Summary of the Invention [Problem to be solved by the invention]

[0005] Criticality adjustment control during startup and shutdown of a pressurized water reactor is performed by adjusting the boron concentration. In this case, if the boron concentration in the cooling water decreases due to equipment malfunction or failure, criticality adjustment becomes difficult. Therefore, it is necessary to detect fluctuations in the boron concentration in the cooling water due to equipment malfunction or failure. Reactor abnormalities due to a decrease in boron concentration can be detected, for example, by measuring an increase in neutron flux or the boron concentration. However, abnormality detection using an increase in neutron flux can have large errors depending on the fuel arrangement in the core, resulting in delayed detection. Furthermore, abnormality detection by measuring boron concentration requires the placement of a concentration meter in the light water piping, which increases costs.

[0006] The present disclosure is intended to solve the above-mentioned problems, and aims to provide a boron concentration determination device, method, and program that can easily detect abnormalities in a nuclear reactor due to fluctuations in boron concentration, thereby preventing the device from becoming more complex and expensive. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, the boron concentration determination device of the present disclosure includes a pure water supply line that supplies pure water, a boric acid water supply line that supplies boric acid water, a boric acid mixed water supply line that supplies boric acid mixed water, which is a mixture of the pure water supplied from the pure water supply line and the boric acid water supplied from the boric acid water supply line, to reactor cooling water, a first flow meter and a second flow meter that measure flow rates of at least two lines among the pure water supply line, the boric acid water supply line, and the boric acid mixed water supply line, and a determination unit that determines an abnormality due to a decrease in boron concentration in the reactor cooling water based on an actual flow rate ratio between a first flow rate measured by the first flow meter and a second flow rate measured by the second flow meter.

[0008] Furthermore, the boron concentration determination method of the present disclosure includes a step of measuring a first flow rate and a second flow rate of at least two lines selected from a pure water supply line that supplies pure water, a boric acid water supply line that supplies boric acid water, and a boric acid mixed water supply line that supplies boric acid mixed water, which is a mixture of the pure water and the boric acid water, to reactor cooling water, and a step of determining an abnormality due to a decrease in boron concentration in the reactor cooling water based on an actual flow rate ratio between the first flow rate and the second flow rate.

[0009] The program of the present disclosure also causes a computer to execute the steps of measuring first and second flow rates of at least two lines out of a pure water supply line that supplies pure water, a boric acid water supply line that supplies boric acid water, and a boric acid mixed water supply line that supplies boric acid mixed water, which is a mixture of the pure water and the boric acid water, to reactor cooling water, and determining an abnormality due to a decrease in boron concentration in the reactor cooling water based on an actual flow rate ratio between the first flow rate and the second flow rate. [Effects of the Invention]

[0010] According to the boron concentration determination device, method, and program disclosed herein, abnormalities due to fluctuations in boron concentration can be easily detected, thereby preventing the device from becoming more complex and expensive. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of a pressurized water reactor to which the boron concentration determination device of this embodiment is applied. [Figure 2] FIG. 2 is a schematic diagram showing a judgment map for judging an abnormality in a nuclear reactor due to a decrease in boron concentration. [Figure 3] FIG. 3 is an explanatory diagram showing the timing of determining an abnormality in a nuclear reactor. [Figure 4] FIG. 4 is a flowchart showing the boron concentration determination method of this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Preferred embodiments of the present disclosure will be described in detail below with reference to the drawings. Note that the present disclosure is not limited to these embodiments, and when there are multiple embodiments, the present disclosure also includes configurations that combine the embodiments. Furthermore, the components in the embodiments include those that can be easily imagined by a person skilled in the art, those that are substantially identical, and those that are within the so-called equivalent range.

[0013] <Pressurized water reactor> FIG. 1 is a schematic diagram showing the configuration of a pressurized water reactor to which the boron concentration determination device of this embodiment is applied.

[0014] In this embodiment, a pressurized water reactor is used as the nuclear reactor. However, the nuclear reactor is not limited to a pressurized water reactor, and the present invention can be applied to other nuclear reactors and various facilities that handle nuclear fuel.

[0015] Pressurized water reactors use light water as the reactor coolant and neutron moderator, producing high-temperature, high-pressure water that does not boil throughout the reactor core. The high-temperature, high-pressure water is sent to a steam generator (described below) to generate steam through heat exchange, and the steam is then sent to a turbine generator to generate electricity.

[0016] As shown in Fig. 1, a pressurized water reactor 11 is connected to a steam generator 14 by a high-temperature side feed piping 12 and a low-temperature side feed piping 13. A primary system cooling water pump 15 is provided on the low-temperature side feed piping 13. The pressurized water reactor 11 and the steam generator 14 are housed inside a reactor containment vessel (not shown).

[0017] Although not shown, the pressurized water reactor 11 has a core inside, which is composed of a plurality of fuel assemblies (fuel rods). The pressurized water reactor 11 also has a plurality of control rods arranged between the fuel assemblies in the core. A control rod drive mechanism controls the reactor output by inserting and removing control rods into and from the core.

[0018] Although not shown, the steam generator 14 is provided with a heat transfer tube group consisting of multiple inverted U-shaped heat transfer tubes inside. The steam generator 14 is provided with an inlet chamber 14a and an outlet chamber 14b at its lower part. The steam generator 14 has an end of the high-temperature side supply pipe 12 connected to the inlet chamber 14a, and an end of the low-temperature side supply pipe 13 connected to the outlet chamber 14b.

[0019] Therefore, in the pressurized water reactor 11, light water is heated as primary system coolant by the fuel assemblies in the core, and the high-temperature primary system coolant is sent to the steam generator 14 through the high-temperature side feed piping 12 while maintained at high pressure. The steam generator 14 generates secondary system steam by exchanging heat between the high-temperature, high-pressure primary system coolant and the secondary system coolant, and the cooled primary system coolant is returned to the pressurized water reactor 11. At this time, the control rod drive mechanism adjusts nuclear fission in the core by inserting and removing control rods into and from the core, thereby adjusting the output of the pressurized water reactor 11.

[0020] The pressurized water reactor 11 is also provided with a chemical volumetric control system (CVCS) 21. A primary cooling water circulation line 22 is provided to the low-temperature side feed piping 13 via a primary cooling water pump 15. The primary cooling water circulation line 22 is provided with a volume control tank 23 and a filling pump 24. Although not shown, the primary cooling water circulation line 22 is also provided with a regenerative heat exchanger, a non-regenerative cooler, a demineralizer, etc. The chemical volumetric control system 21 is provided in the primary cooling water circulation line 22.

[0021] The chemical volume control system 21 has a primary cooling water supply line (pure water supply line) 31, a boric acid water supply line 32, and a boric acid mixed water supply line 33. One end of the boric acid mixed water supply line 33 is connected to the primary cooling water circulation line 22. The other end of the boric acid mixed water supply line 33 is connected to one end of the primary cooling water supply line 31 and one end of the boric acid water supply line 32 via a mixer 34.

[0022] The primary cooling water supply line 31 is provided with a flow control valve 41, a pure water flow meter 42, an isolation valve 43, and a make-up water pump 44, and is connected to a primary pure water tank 45 at its other end. The boric acid water supply line 32 is provided with a flow control valve 51, a boric acid water flow meter 52, and a boric acid water pump 53, and is connected to a boric acid water tank 54 at its other end. The boric acid mixed water supply line 33 is provided with a flow control valve 61 and a boric acid mixed water flow meter 62. Here, each of the flow meters 42, 52, and 62 is, for example, a differential pressure flow meter, but other types may also be used. Furthermore, for safety reasons, it is preferable that the flow meters 41, 52, and 62 are each provided in multiple locations.

[0023] The flow rate control valve 41 can adjust the amount of pure water supplied in the primary cooling water supply line 31 by adjusting its opening. The pure water flow meter 42 can measure the amount of pure water supplied flowing through the primary cooling water supply line 31. The isolation valve 43 can stop the supply of pure water by closing it, regardless of the opening of the flow rate control valve 41. The makeup water pump 44 can supply pure water by operating it. The primary pure water tank 45 stores pure water as makeup water for the primary cooling water.

[0024] The flow rate control valve 51 can adjust the amount of boric acid water supplied in the boric acid water supply line 32 by adjusting its opening. The boric acid water flow meter 52 can measure the amount of boric acid water supplied through the boric acid water supply line 32. The boric acid water pump 53 can supply boric acid water by operating. The boric acid water tank 54 stores boric acid water of a predetermined concentration.

[0025] The flow rate adjustment valve 61 can adjust the opening rate to adjust the supply rate of boric acid mixed water in the boric acid mixed water supply line 33. The boric acid mixed water flow meter 62 can measure the supply rate of boric acid mixed water flowing through the boric acid mixed water supply line 33.

[0026] The control device 71 is connected to the filling pump 24, the flow rate control valves 41, 51, and 61, the flow meters 42, 52, and 62, the isolation valve 43, and the pumps 44 and 53. By operating the filling pump 24, the control device 71 can circulate a portion of the primary system cooling water to the primary system cooling water circulation line 22. The control device 71 can adjust the opening degree of the flow rate control valves 41, 51, and 61. The control device 71 also receives the flow rates of the pure water, the boric acid water, and the boric acid-mixed water as measurement results of the flow meters 42, 52, and 62. The control device 71 can also open and close the isolation valve 43. The control device 71 can also operate and close the pumps 44 and 53.

[0027] The control device 71 is a controller, and is realized by, for example, a CPU (Central Processing Unit) or an MPU (Micro Processing Unit) executing various programs stored in a storage unit using a RAM as a working area.

[0028] The control device 71 is connected to an operation unit 72 and a storage unit 73. An operator can input various data to the control device 71 by operating the operation unit 72. The operation unit 72 is, for example, a keyboard or a touch-type display. The storage unit 73 stores an abnormality determination map, which will be described later, and the like.

[0029] Therefore, the control device 71 controls the chemical volume control system 21 to supply pure water or boric acid water to the primary system cooling water (reactor cooling water) that cools the pressurized water reactor 11, thereby adjusting the boron concentration in the primary system cooling water.

[0030] That is, when the filling pump 24 is operated, a portion of the primary cooling water flowing through the high-temperature side supply pipe 12 and the low-temperature side supply pipe 13 can be taken in and circulated into the primary cooling water circulation line 22. At this time, the volume control tank 23 purifies the primary cooling water and absorbs volume fluctuations due to boron concentration adjustment, etc.

[0031] Then, when the control device 71 opens the flow control valve 41 and operates the makeup water pump 44 while keeping the isolation valve 43 open, it can supply pure water stored in the primary system pure water tank 45 from the primary system cooling water makeup line 31 to the boric acid mixed water supply line 33 through the mixer 34. Furthermore, when the control device 71 opens the flow control valve 51 and operates the boric acid water pump 53, it can supply boric acid water stored in the boric acid water tank 54 from the boric acid water supply line 32 through the mixer 34 to the boric acid mixed water supply line 33. When the control device 71 opens the flow control valve 61, it can supply boric acid mixed water produced by mixing the pure water and boric acid water in the mixer 34 from the boric acid mixed water supply line 33 to the primary system cooling water circulation line 22.

[0032] Here, the control device 71 adjusts the aperture of the flow rate control valve 41 of the primary cooling water make-up line 31 and the aperture of the flow rate control valve 51 of the boric acid water supply line 32 to adjust the boron concentration in the boric acid mixed water supplied from the boric acid mixed water supply line 33 to the primary cooling water circulation line 22. The control device 71 also adjusts the aperture of the flow rate control valve 61 of the boric acid mixed water supply line 33 to adjust the flow rate of the boric acid mixed water supplied from the boric acid mixed water supply line 33 to the primary cooling water circulation line 22. As a result, the control device 71 can adjust the boron concentration in the primary cooling water flowing through the high-temperature side feed pipe 12 and the low-temperature side feed pipe 13 connected to the primary cooling water circulation line 22 by adjusting the boron concentration and flow rate of the boric acid mixed water supplied to the primary cooling water circulation line 22.

[0033] The control device 71 also feedback controls the opening of each of the flow rate adjustment valves 41, 51, and 61 based on the flow rates of the pure water, boric acid water, and boric acid-mixed water input from the flow meters 42, 52, and 62.

[0034] <Boron concentration determination device> As shown in FIG. 1, the boron concentration determination device 70 includes a primary cooling water supply line 31, a boric acid water supply line 32, a boric acid mixed water supply line 33, a first flow meter, a second flow meter, and a determination unit.

[0035] In this embodiment, the first flow meter is a pure water flow meter 42 provided in the primary system cooling water supply line 31, and the second flow meter is a boric acid mixed water flow meter 62 provided in the boric acid mixed water supply line 33. In addition, the control device 71 functions as the determination unit.

[0036] That is, the pure water flow meter 42 as a first flow meter measures the flow rate of pure water as a first flow meter in the primary-system cooling water make-up line 31. Furthermore, the boric acid mixed water flow meter 62 as a second flow meter measures the flow rate of boric acid mixed water as a second flow meter in the boric acid mixed water supply line 33. Then, the control device 71 as a determination unit determines an abnormality due to a decrease in the boron concentration in the primary-system cooling water based on the actual flow rate ratio between the flow rate of pure water measured by the pure water flow meter 42 and the flow rate of boric acid mixed water measured by the boric acid mixed water flow meter 62.

[0037] A standard boron concentration in the primary cooling water is set for the pressurized water reactor 11 in order to properly maintain the pressurized water reactor 11. Here, the standard boron concentration is the lower limit of the boron concentration in the primary cooling water for safely operating the pressurized water reactor 11. The control device 71 controls the chemical volume control system 21 as necessary to supply pure water, boric acid water, or boric acid mixed water to the primary cooling water, thereby adjusting the boron concentration in the primary cooling water to be maintained at or above the standard boron concentration.

[0038] A reference flow rate ratio between the flow rate of pure water (first flow rate) and the flow rate of boric acid mixed water (second flow rate) is set for the pressurized water reactor 11 in order to maintain the primary system cooling water at a reference boron concentration or higher. Here, the reference flow rate ratio is the ratio of the flow rate of pure water to the flow rate of boric acid mixed water, and is the upper limit of the flow rate ratio for safely operating the pressurized water reactor 11. The control device 71 compares the reference flow rate ratio with the actual flow rate ratio to determine whether there is an abnormality due to a decrease in the boron concentration.

[0039] The control device 71 controls the opening of the flow control valves 41, 51, and 61 and the operation of the pumps 44 and 53, but there is a possibility that the control device 71, the flow control valves 41, 51, and 61, the flow meters 42, 52, and 62, and the pumps 44 and 53, etc. may malfunction or fail. If various devices malfunction or fail, the boron in the primary system coolant is diluted. Therefore, the control device 71 detects the dilution of boron in the primary system coolant by comparing the reference flow rate ratio with the actual flow rate ratio, and determines whether an abnormality in the pressurized water reactor 11 has occurred due to a decrease in the boron concentration.

[0040] When the control device 71 determines that an abnormality has occurred in the pressurized water reactor 11 due to a decrease in the boron concentration, it closes the isolation valve 43. This stops the supply of pure water through the primary system coolant supply line 31, for which the isolation valve 43 has been closed, and suppresses the dilution of boron in the primary system coolant.

[0041] In the above-described embodiment, the first flow meter is the pure water flow meter 42 and the second flow meter is the boric acid mixed water flow meter 62, but the present invention is not limited to this configuration.

[0042] For example, the first flow meter may be a pure water flow meter 42 provided in the primary cooling water supply line 31, and the second flow meter may be a boric acid water flow meter 52 provided in the boric acid water supply line 32. In this case, the control device 71 as a determination unit determines an abnormality due to a decrease in the boron concentration in the primary cooling water based on the actual flow rate ratio between the flow rate of pure water measured by the pure water flow meter 42 and the flow rate of boric acid water measured by the boric acid water flow meter 52.

[0043] Furthermore, the first flow meter may be a boric acid water flow meter 52 provided in the boric acid water supply line 32, and the second flow meter may be a boric acid mixed water flow meter 62 provided in the boric acid mixed water supply line 33. In this case, the control device 71 as a determination unit determines an abnormality due to a decrease in the boron concentration in the primary system cooling water based on the actual flow rate ratio between the flow rate of the boric acid water measured by the boric acid water flow meter 52 and the flow rate of the boric acid mixed water measured by the boric acid mixed water flow meter 62.

[0044] Furthermore, the control device 71 as a judgment unit may judge an abnormality due to a decrease in the boron concentration in the primary system cooling water based on the actual flow rate ratio of the flow rate of pure water measured by the pure water flow meter 42, the flow rate of boric acid water measured by the boric acid water flow meter 52, and the flow rate of boric acid mixed water measured by the boric acid mixed water flow meter 62.

[0045] <Abnormality detection map> FIG. 2 is a schematic diagram showing a judgment map for judging an abnormality in a nuclear reactor due to a decrease in boron concentration.

[0046] As shown in FIG. 2, the control device 71 compares a preset reference flow rate ratio with an actual flow rate ratio calculated from the measurement results of the flow meters 42 and 62 to determine an abnormality due to a decrease in boron concentration. Here, the reference flow rate ratio and the actual flow rate ratio are the ratio of the flow rate of pure water to the flow rate of boric acid-mixed water. The reference flow rate ratio is set based on the reference boron concentration. Then, a first threshold value L1 is set based on the reference flow rate ratio. A second threshold value L2 is set by adding a margin M to the first threshold value L1. Here, a normal region A1 is set for the second threshold value L2, and an abnormal region A2 is set for the first threshold value L1. The region between the normal region A1 and the abnormal region A2 is a non-interference region. Note that the non-interference region taking into account the margin M is set taking into account measurement errors of the flow meters 42 and 62 and the operating margin of the pressurized water reactor 11. Note that the normal region A1 and the abnormal region A2 may be set for the first threshold value L1 without considering the margin M.

[0047] When the actual flow rate ratio is in the normal region A1, the control device 71 determines that the pressurized water reactor 11 is normal due to a decrease in the boron concentration in the primary cooling water. On the other hand, when the actual flow rate ratio is not in the normal region A1 but in the abnormal region A2, the control device 71 determines that the pressurized water reactor 11 is abnormal due to a decrease in the boron concentration in the primary cooling water. The first threshold value L1 (abnormal region A2), the second threshold value L2 (normal region A1), and the margin M can be changed depending on the criticality conditions of the pressurized water reactor 11.

[0048] <Abnormality determination time> FIG. 3 is an explanatory diagram showing the timing of determining an abnormality in a nuclear reactor.

[0049] As shown in FIG. 3, the pressurized water reactor 11 starts to start up and increase the power output at time t1, starts operation with the power output maintained constant (Pa) at time t2, reduces the power output at time t3, and shuts down at time t4.

[0050] The control device 71 executes a process for determining an abnormality due to a decrease in the boron concentration in the primary system coolant before and after the start-up and shutdown of the pressurized water reactor 11.

[0051] During startup (t1 to t2), the pressurized water reactor 11 undergoes core refueling, and therefore the boron concentration in the primary coolant is higher than the reference boron concentration. Therefore, the control device 71 opens only the flow control valve 41, supplies only pure water to the primary coolant circulation line 22, and reduces the boron concentration in the primary coolant to the reference boron concentration. The dilution of the boron concentration in the primary coolant at this time is normal, and the determination of an abnormality by the control device 71 based on the actual flow rate ratio between the flow rate of pure water and the flow rate of boric acid-mixed water would be an erroneous determination. Therefore, the control device 71 does not execute a process for determining an abnormality due to a decrease in boron concentration during startup of the pressurized water reactor 11.

[0052] Furthermore, while the pressurized water reactor 11 is shut down (t3 to t4), the temperature of the primary cooling water is high. Therefore, the control device 71 increases the opening of the flow control valves 41 and 51 to increase the criticality of the pressurized water reactor 11, while supplying make-up water with a high boron concentration to compensate for the contraction of the primary cooling water due to the drop in temperature. The enrichment of the boron concentration in the primary cooling water at this time is normal, and the control device 71 may execute an abnormality determination process based on the actual flow rate ratio between the flow rate of pure water and the flow rate of boric acid-mixed water, but the make-up of the primary cooling water would result in an erroneous determination. Therefore, the control device 71 does not execute a process to determine an abnormality due to a drop in boron concentration while the pressurized water reactor 11 is shut down.

[0053] Furthermore, during operation of the pressurized water reactor 11 (t2 to t3), the control device 71 opens the flow control valve 41 and supplies pure water to the primary cooling water, thereby diluting the boron concentration in the primary cooling water. The dilution of the boron concentration in the primary cooling water at this time is normal, and the determination of an abnormality by the control device 71 based on the actual flow rate ratio between the flow rate of pure water and the flow rate of boric acid-mixed water would be an erroneous determination. Therefore, even during operation of the pressurized water reactor 11, the control device 71 does not execute a process for determining an abnormality due to a decrease in boron concentration when diluting the primary cooling water for criticality control.

[0054] That is, the control device 71 does not determine an abnormality due to a decrease in the boron concentration in the primary cooling water during the period from the start-up (t1) to the shutdown (t4) of the pressurized water reactor 11.

[0055] Then, when the flow rate of the pure water or the flow rate of the boric acid mixed water fluctuates due to adjustment of the opening of each flow control valve 41, 61 before the start-up (t0 to t1) and after the shutdown (t4 to t5) of the pressurized water reactor 11, the control device 71 determines, after a predetermined waiting time has elapsed, whether there is an abnormality due to a decrease in the boron concentration in the primary system cooling water based on the actual flow rate ratio of the pure water and the boric acid mixed water.

[0056] <Boron concentration determination method> FIG. 4 is a flowchart showing the boron concentration determination method of this embodiment.

[0057] The boron concentration determination method includes the steps of measuring first and second flow rates of at least two lines selected from a primary system cooling water supply line (pure water supply line) 31 that supplies pure water, a boric acid water supply line 32 that supplies boric acid water, and a boric acid mixed water supply line 33 that supplies boric acid mixed water, which is a mixture of pure water and boric acid water, to the primary system cooling water (reactor cooling water), and determining whether there is an abnormality due to a decrease in the boron concentration in the primary system cooling water based on the actual flow rate ratio between the first flow rate and the second flow rate.

[0058] The boron concentration determination method will be specifically described below. As shown in Figures 1 and 4, in step S11, the control device 71 determines whether or not a boron concentration determination condition is met. The boron concentration determination condition is that the pressurized water reactor 11 is maintained in a state before startup or a state after shutdown. Here, if the control device 71 determines that the boron concentration determination condition is not met (No), it exits this routine.

[0059] On the other hand, if the control device 71 determines that the boron concentration determination condition is met (Yes), then in step S12, the control device 71 determines whether the apertures of the flow rate control valves 41, 51, and 61 have been changed. If the control device 71 determines that the apertures of the flow rate control valves 41, 51, and 61 have been changed (Yes), then in step S13, the control device 71 determines whether a standby time has elapsed since the apertures of the flow rate control valves 41, 51, and 61 were changed. If the control device 71 determines that the standby time has not elapsed since the apertures of the flow rate control valves 41, 51, and 61 were changed (No), then the control device 71 maintains this state. If the control device 71 determines that the standby time has elapsed since the apertures of the flow rate control valves 41, 51, and 61 were changed (Yes), then the control device 71 proceeds to step S14. If the control device 71 determines that the apertures of the flow rate control valves 41, 51, and 61 have not been changed (No) in step S12, then the control device 71 proceeds to step S14.

[0060] In step S14, the control device 71 acquires the flow rate of pure water in the primary cooling water supply line 31 and the flow rate of boric acid mixed water in the boric acid mixed water supply line 33 as detection results of the flow rate adjustment valves 41, 61. In step S15, the control device 71 calculates an actual flow rate ratio (flow rate of pure water / flow rate of boric acid mixed water), which is the ratio of the flow rate of pure water to the flow rate of boric acid mixed water. Then, in step S16, the control device 71 determines whether the actual flow rate ratio is within a normal range. In this case, the control device 71 determines whether the actual flow rate ratio is within a normal range using an abnormality determination map (see FIG. 2) stored in the memory unit 73.

[0061] If the control device 71 determines that the actual flow rate ratio is in the normal range (Yes), the boron concentration of the primary cooling water is not diluted, and therefore the control device 71 exits this routine. On the other hand, if the control device 71 determines that the actual flow rate ratio is not in the normal range but in the abnormal range (No), the boron concentration of the primary cooling water is diluted, and therefore the control device 71 closes the isolation valve 43 in step S17. In other words, if the control device 71 determines that the actual flow rate ratio is in the abnormal range, for example, it is highly likely that the flow control valve 41 has been opened due to a malfunction or failure, and pure water is being supplied to the primary cooling water circulation line 22 through the primary cooling water supply line 31 and the boric acid water supply line 32. Therefore, the isolation valve 43 is closed.

[0062] When the isolation valve 43 is closed, the supply of pure water to the primary cooling water circulation line 22 through the primary cooling water supply line 31 and the boric acid water supply line 32 is stopped, and the dilution of the boron concentration in the primary cooling water is suppressed. After that, the pressurized water reactor 11 is shut down.

[0063] [Effects of this embodiment] The boron concentration determination device according to the first aspect includes a primary system cooling water supply line (pure water supply line) 31 that supplies pure water, a boric acid water supply line 32 that supplies boric acid water, a boric acid mixed water supply line 33 that supplies boric acid mixed water, which is a mixture of pure water supplied from the primary system cooling water supply line 31 and boric acid water supplied from the boric acid water supply line 32, to the primary system cooling water (reactor cooling water), a first flow meter and a second flow meter that measure the flow rates of at least two of the primary system cooling water supply line 31, the boric acid water supply line 32, and the boric acid mixed water supply line 33, and a control device (determination unit) 71 that determines an abnormality due to a decrease in the boron concentration in the primary system cooling water based on the actual flow rate ratio between the first flow rate measured by the first flow meter and the second flow rate measured by the second flow meter.

[0064] The boron concentration determination device according to the first aspect determines an abnormality due to a decrease in the boron concentration in the primary cooling water based on the actual flow rate ratio of at least two of the flow rates of pure water, boric acid water, and boric acid-mixed water. Therefore, an abnormality due to a change in the boron concentration can be easily detected using existing equipment, and the complexity and cost of the device can be reduced.

[0065] The boron concentration determining device according to the second aspect is the boron concentration determining device according to the first aspect, further comprising: the first flow meter is a pure water flow meter 42 provided in the primary cooling water supply line 31; the second flow meter is a boric acid mixed water flow meter 62 provided in the boric acid mixed water supply line 33; and the control device 71 determines an abnormality due to a decrease in the boron concentration in the primary cooling water based on the ratio of the actual flow rates of the pure water measured by the pure water flow meter 42 and the boric acid mixed water measured by the boric acid mixed water flow meter. This makes it possible to appropriately detect an abnormality due to a fluctuation in the boron concentration.

[0066] The boron concentration determination device according to the third aspect is the boron concentration determination device according to the first aspect, further comprising: the first flow meter being a pure water flow meter 42 provided in the primary cooling water supply line 31; the second flow meter being a boric acid water flow meter 52 provided in the boric acid water supply line 32; and the control device 71 determining an abnormality due to a decrease in the boron concentration in the primary cooling water based on the ratio of the actual flow rates of the pure water measured by the pure water flow meter 42 and the boric acid water measured by the boric acid water flow meter 52. This allows for appropriate detection of an abnormality due to a fluctuation in the boron concentration.

[0067] In the boron concentration determination device according to the fourth aspect, the first flow meter is a boric acid water flow meter 52 provided in the boric acid water supply line 32, and the second flow meter is a boric acid mixed water flow meter 62 provided in the boric acid mixed water supply line 33, and the control device 71 determines an abnormality due to a decrease in the boron concentration in the primary system cooling water based on the ratio of the flow rate of the boric acid water measured by the boric acid water flow meter 52 to the actual flow rate of the boric acid mixed water measured by the boric acid mixed water flow meter 62. This makes it possible to appropriately detect an abnormality due to a fluctuation in the boron concentration.

[0068] A boron concentration determination device according to a fifth aspect is the boron concentration determination device according to any one of the first to fourth aspects, and further, when the first flow rate or the second flow rate fluctuates, the control device 71 determines an abnormality due to a decrease in the boron concentration in the primary-system coolant based on the actual flow rate ratio after a preset, predetermined standby time has elapsed. As a result, for example, when the openings of the flow control valves 41, 51, and 61 are changed to cause the first flow rate or the second flow rate to fluctuate, it takes a predetermined time for the effect to appear in the flow meters 42, 52, and 62, and by determining an abnormality using the actual flow rate ratio after the standby time has elapsed, highly accurate determination can be made.

[0069] A boron concentration determination device according to a sixth aspect is the boron concentration determination device according to any one of the first to fifth aspects, further comprising: a reference boron concentration in the primary cooling water for properly maintaining the pressurized water reactor 11; a reference flow rate ratio between a first flow rate and a second flow rate for maintaining the primary cooling water at the reference boron concentration; and a control device 71 compares the reference flow rate ratio with an actual flow rate ratio to determine an abnormality due to a decrease in the boron concentration. This allows the flow rates measured by the flow meters 42, 52, and 62 to be directly used in determining an abnormality, thereby simplifying the determination processing logic.

[0070] The boron concentration determination device according to the seventh aspect is the boron concentration determination device according to the sixth aspect, and further includes a normal region in which the reference boron concentration is maintained by adding a margin to the reference flow rate ratio, and the control device 71 determines that an abnormality has occurred when the actual flow rate ratio is not within the normal region. This allows for the malfunction of various devices to be considered as a margin when determining an abnormality, thereby suppressing hunting in the abnormality determination.

[0071] The boron concentration determination device according to the eighth aspect is the boron concentration determination device according to the seventh aspect, and further, the normal region is changeable according to the criticality condition of the pressurized water reactor 11. This allows for highly accurate abnormality determination according to the configuration of the pressurized water reactor 11, etc.

[0072] The boron concentration determination device according to a ninth aspect is the boron concentration determination device according to any one of the first to eighth aspects, further comprising an isolation valve 43 provided in the primary system coolant supply line 31, and the control device 71 actuating the isolation valve 43 to close it when determining an abnormality. This suppresses a decrease in the boron concentration in the primary system coolant, thereby ensuring the safety of the pressurized water reactor 11.

[0073] The boron concentration determination device according to a tenth aspect is the boron concentration determination device according to any one of the first to ninth aspects, and further, the control device 71 determines an abnormality due to a decrease in boron concentration in the primary system coolant before and after startup and shutdown of the pressurized water reactor 11. This allows appropriate determination of an abnormality due to a fluctuation in boron concentration.

[0074] A boron concentration determination method according to an eleventh aspect includes the steps of measuring first and second flow rates in at least two lines selected from a primary system cooling water supply line (pure water supply line) 31 that supplies pure water, a boric acid water supply line 32 that supplies boric acid water, and a boric acid mixed water supply line 33 that supplies boric acid mixed water, which is a mixture of pure water and boric acid water, to primary system cooling water (reactor cooling water), and determining an abnormality due to a decrease in boron concentration in the primary system cooling water based on the actual flow rate ratio between the first flow rate and the second flow rate. This allows for easy detection of an abnormality due to a change in boron concentration using existing equipment, and prevents the device from becoming complicated and expensive.

[0075] A program according to a twelfth aspect causes a computer to execute the steps of measuring first and second flow rates of at least two lines selected from a primary system cooling water supply line (pure water supply line) 31 that supplies pure water, a boric acid water supply line 32 that supplies boric acid water, and a boric acid mixed water supply line 33 that supplies boric acid mixed water, which is a mixture of pure water and boric acid water, to the primary system cooling water (reactor cooling water), and determining an abnormality due to a decrease in boron concentration in the primary system cooling water based on the actual flow rate ratio between the first flow rate and the second flow rate. This makes it possible to easily detect an abnormality due to a fluctuation in boron concentration using existing equipment, and prevents the device from becoming complicated and expensive.

[0076] In the above-described embodiment, an abnormality due to a decrease in boron concentration is determined by comparing the actual flow rate ratio of at least two flow rates, namely, the flow rate of pure water, the flow rate of boric acid water, and the flow rate of boric acid-mixed water, with a reference flow rate ratio set based on a reference boron concentration, but this configuration is not limited to this. For example, the boron concentration in the primary system cooling water may be estimated based on the actual flow rate ratio of at least two flow rates, namely, the flow rate of pure water, the flow rate of boric acid water, and the flow rate of boric acid-mixed water, and the estimated boron concentration may be compared with the reference boron concentration to determine an abnormality due to a decrease in boron concentration. [Explanation of symbols]

[0077] 11 Pressurized water reactor 12 High temperature side feed piping 13 Low temperature side feed piping 14 Steam generator 15 Primary cooling water pump 21 Chemical volume control system 22 Primary cooling water circulation line 23 Volume control tank 24 Filling pump 31 Primary cooling water supply line (pure water supply line) 32 Boric acid water supply line 33 Boric acid mixed water supply line 34 Mixer 41 Flow control valve 42 Pure water flow meter 43 Isolation valve 44 Make-up water pump 45 Primary pure water tank 51 Flow control valve 52 Boric acid water flow meter 53 Boric Acid Water Pump 54 Boric Acid Water Tank 61 Flow control valve 62 Boric Acid Mixed Water Flow Meter 71 Control device (judgment unit) 72 Control section 73 Memory section

Claims

1. a pure water supply line for supplying pure water; a boric acid water supply line for supplying boric acid water; a boric acid mixed water supply line that supplies boric acid mixed water obtained by mixing the pure water supplied from the pure water supply line and the boric acid water supplied from the boric acid water supply line to the reactor cooling water; a first flow meter and a second flow meter for measuring flow rates of at least two lines among the pure water supply line, the boric acid water supply line, and the boric acid mixed water supply line; a determination unit that determines an abnormality due to a decrease in boron concentration in the reactor cooling water based on an actual flow rate ratio between a first flow rate measured by the first flow meter and a second flow rate measured by the second flow meter; A boron concentration determination device comprising:

2. the first flow meter is provided on the pure water supply line, and the second flow meter is provided on the boric acid mixed water supply line, and the determination unit determines an abnormality caused by a decrease in boron concentration in the reactor cooling water based on an actual flow rate ratio between a flow rate of the pure water as the first flow rate measured by the first flow meter and a flow rate of the boric acid mixed water as the second flow rate measured by the second flow meter. The boron concentration determining device according to claim 1 .

3. the first flow meter is provided on the pure water supply line, and the second flow meter is provided on the boric acid water supply line, and the determination unit determines an abnormality due to a decrease in boron concentration in the reactor cooling water based on an actual flow rate ratio between a flow rate of the pure water as the first flow rate measured by the first flow meter and a flow rate of the boric acid water as the second flow rate measured by the second flow meter. The boron concentration determining device according to claim 1 .

4. the first flow meter is provided in the boric acid water supply line, and the second flow meter is provided in the boric acid mixed water supply line, and the determination unit determines an abnormality due to a decrease in boron concentration in the reactor cooling water based on an actual flow rate ratio between a flow rate of the boric acid water as the first flow rate measured by the first flow meter and a flow rate of the boric acid mixed water as the second flow rate measured by the second flow meter. The boron concentration determining device according to claim 1 .

5. the determination unit determines an abnormality due to a decrease in boron concentration in the reactor cooling water based on the actual flow rate ratio after a predetermined waiting time has elapsed when the first flow rate or the second flow rate has fluctuated. The boron concentration determining device according to any one of claims 1 to 4.

6. a reference boron concentration in the reactor cooling water for maintaining the reactor properly is set, a reference flow rate ratio between the first flow rate and the second flow rate for maintaining the reactor cooling water at the reference boron concentration is set, and the determination unit compares the reference flow rate ratio with the actual flow rate ratio to determine an abnormality due to a decrease in the boron concentration; The boron concentration determining device according to claim 1 .

7. a normal region in which the reference boron concentration is maintained is set by adding a margin to the reference flow rate ratio, and the determination unit determines that an abnormality has occurred when the actual flow rate ratio is not within the normal region; The boron concentration determining device according to claim 6.

8. The normal region is changeable depending on the critical condition of the reactor. The boron concentration determining device according to claim 7.

9. an isolation valve is provided in the pure water supply line, and the determination unit operates the isolation valve to close the valve when determining that an abnormality has occurred; The boron concentration determining device according to claim 1 .

10. the determination unit determines an abnormality caused by a decrease in boron concentration in the reactor cooling water before and after the start-up and shutdown of the reactor. The boron concentration determining device according to claim 1 .

11. measuring a first flow rate and a second flow rate of at least two lines selected from a pure water supply line for supplying pure water, a boric acid water supply line for supplying boric acid water, and a boric acid mixed water supply line for supplying boric acid mixed water obtained by mixing the pure water and the boric acid water to reactor cooling water; determining an abnormality due to a decrease in boron concentration in the reactor cooling water based on an actual flow rate ratio between the first flow rate and the second flow rate; A method for determining boron concentration comprising the steps of:

12. measuring a first flow rate and a second flow rate of at least two lines selected from a pure water supply line for supplying pure water, a boric acid water supply line for supplying boric acid water, and a boric acid mixed water supply line for supplying boric acid mixed water obtained by mixing the pure water and the boric acid water to reactor cooling water; determining an abnormality due to a decrease in boron concentration in the reactor cooling water based on an actual flow rate ratio between the first flow rate and the second flow rate; A program that causes a computer to execute the following.

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