JP7720281B2 - Boron concentration determination device, method, and program - Google Patents

Description

This disclosure relates to a boron concentration determination device, a boron concentration determination method, and a program.

For example, a nuclear power plant with a pressurized water reactor (PWR) uses light water as a 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 to generate steam through heat exchange, and the steam is then sent to a turbine generator to generate electricity.

Pressurized water reactors can control reactivity through control rod operation and chemical volumetric control (adjusting the boron concentration). The power output of a pressurized water reactor is controlled by controlling the control rods after maintaining the boron concentration of the cooling water (light water) at a predetermined value through chemical volumetric control. Examples of such reactor control include those described in the following patent documents:

Japanese Unexamined Patent Publication No. 60-146187 Patent No. 2734483

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. For this reason, it is necessary to detect fluctuations in the boron concentration in the cooling water due to equipment malfunction or failure. Reactor abnormalities caused by decreases 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 be subject to large errors depending on the fuel arrangement in the core, resulting in delayed detection. Furthermore, detecting abnormalities by measuring boron concentration requires the placement of concentration meters in light water piping, etc., which increases costs.

The present disclosure aims to solve the above-mentioned problems by providing a boron concentration determination device, method, and program that can easily detect reactor abnormalities caused by fluctuations in boron concentration, thereby preventing the device from becoming more complex and expensive.

To achieve the above-mentioned objective, 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 the flow rates of at least two of 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 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.

The boron concentration determination method disclosed herein also includes the steps of measuring a first flow rate and a second flow rate in at least two lines, namely, 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 the reactor cooling water, and determining whether an abnormality has occurred due to a decrease in the boron concentration in the reactor cooling water based on the actual flow rate ratio between the first flow rate and the second flow rate.

The program disclosed herein also causes a computer to execute the following steps: measuring a first flow rate and a second flow rate in 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 determining whether an abnormality has occurred due to a decrease in the boron concentration in the reactor cooling water based on the actual flow rate ratio between the first flow rate and the second flow rate.

The boron concentration determination device, method, and program disclosed herein can easily detect abnormalities caused by fluctuations in boron concentration, thereby preventing the device from becoming too complicated and expensive.

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. FIG. 2 is a schematic diagram showing a judgment map for judging an abnormality in the nuclear reactor due to a decrease in boron concentration. FIG. 3 is an explanatory diagram showing the timing of determining an abnormality in a nuclear reactor. FIG. 4 is a flowchart showing the boron concentration determination method of this embodiment.

Preferred embodiments of the present disclosure are 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, they also include configurations that combine the various embodiments. Furthermore, the components in the embodiments include those that would 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.

<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.

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

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 entire 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.

As shown in FIG. 1, a pressurized water reactor 11 is connected to a steam generator 14 by a high-temperature side supply pipe 12 and a low-temperature side supply pipe 13. A primary system cooling water pump 15 is provided on the low-temperature side supply pipe 13. The pressurized water reactor 11 and the steam generator 14 are contained inside a reactor containment vessel (not shown).

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

The steam generator 14 has a heat transfer tube bank (not shown) made up of multiple inverted U-shaped heat transfer tubes inside. The steam generator 14 has an inlet chamber 14a and an outlet chamber 14b at its bottom. The end of the high-temperature side supply pipe 12 is connected to the inlet chamber 14a of the steam generator 14, and the end of the low-temperature side supply pipe 13 is connected to the outlet chamber 14b.

For this reason, in the pressurized water reactor 11, light water is heated by the fuel assemblies in the core as primary system coolant, 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 from the core, thereby adjusting the output of the pressurized water reactor 11.

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

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.

The primary cooling water supply line 31 is equipped with a flow control valve 41, a pure water flow meter 42, an isolation valve 43, and a supply 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 equipped 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 equipped 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. It is also preferable to install the flow meters 41, 52, and 62 in multiple locations for safety reasons.

The flow 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 through the primary cooling water supply line 31. The isolation valve 43 can be closed to stop the supply of pure water regardless of the opening of the flow control valve 41. The makeup water pump 44 can be operated to supply pure water. The primary pure water tank 45 stores pure water as makeup water for the primary cooling water.

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 flowing 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.

The flow rate control valve 61 can adjust the amount of boric acid mixed water supplied through the boric acid mixed water supply line 33 by adjusting its opening. The boric acid mixed water flow meter 62 can measure the amount of boric acid mixed water supplied through the boric acid mixed water supply line 33.

The control device 71 is connected to the filling pump 24, the flow 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 control valves 41, 51, and 61. The control device 71 also receives the flow rates of pure water, boric acid water, and boric acid-mixed water as measurement results from 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.

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

The control device 71 is connected to an operation unit 72 and a memory unit 73. The operation unit 72 can be operated by an operator to input various data into the control device 71. The operation unit 72 is, for example, a keyboard or a touch-sensitive display. The memory unit 73 stores the abnormality determination map, which will be described later.

Therefore, by controlling the chemical volume control system 21, the control device 71 can 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.

In other words, 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 in the primary cooling water circulation line 22. At this time, the volume control tank 23 purifies the primary cooling water and absorbs volume fluctuations caused by boron concentration adjustments, etc.

The control device 71 can then open the flow control valve 41 and operate the makeup water pump 44 while keeping the isolation valve 43 open, thereby supplying 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. The control device 71 can also open the flow control valve 51 and operate the boric acid water pump 53, thereby supplying 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. The control device 71 can then open the flow control valve 61, thereby supplying the 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.

Here, the control device 71 adjusts the aperture of the flow control valve 41 on the primary cooling water supply line 31 and the aperture of the flow control valve 51 on 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 control valve 61 on 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, by adjusting the boron concentration and flow rate of the boric acid mixed water supplied to the primary cooling water circulation line 22, the control device 71 can adjust the boron concentration in the primary cooling water flowing through the high-temperature side supply pipe 12 and the low-temperature side supply pipe 13 connected to the primary cooling water circulation line 22.

In addition, the control device 71 feedback-controls the opening degree of each flow control valve 41, 51, 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, 62.

<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.

In this embodiment, the first flow meter is a pure water flow meter 42 provided in the primary 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. The determination unit is also functioned by the control device 71.

That is, the pure water flow meter 42, acting as a first flow meter, measures the flow rate of pure water in the primary cooling water supply line 31. The boric acid mixed water flow meter 62, acting as a second flow meter, measures the flow rate of boric acid mixed water in the boric acid mixed water supply line 33. The control device 71, acting as an evaluation unit, determines whether an abnormality has occurred 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 mixed water measured by the boric acid mixed water flow meter 62.

A standard boron concentration in the primary cooling water for the pressurized water reactor 11 is set to maintain the pressurized water reactor 11 properly. Here, the standard boron concentration is the lower limit of the boron concentration in the primary cooling water for safe operation of 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.

The pressurized water reactor 11 has a set standard 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) for maintaining the primary system cooling water at a standard boron concentration or higher. Here, the standard 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 safe operation of the pressurized water reactor 11. The control device 71 compares the standard flow rate ratio with the actual flow rate ratio to determine whether an abnormality has occurred due to a decrease in boron concentration.

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, flow control valves 41, 51, and 61, flow meters 42, 52, and pumps 44 and 53 may malfunction or fail. Malfunctions or failures in various devices cause the boron in the primary cooling water to be diluted. Therefore, the control device 71 detects the dilution of boron in the primary cooling water 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 boron concentration.

When the control device 71 determines that an abnormality in the pressurized water reactor 11 has occurred due to a decrease in boron concentration, it operates the isolation valve 43 to close it. This stops the supply of pure water through the primary system coolant supply line 31, with the isolation valve 43 now closed, and suppresses the dilution of boron in the primary system coolant.

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

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 acting as the 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 pure water flow rate measured by the pure water flow meter 42 and the boric acid water flow rate measured by the boric acid water flow meter 52.

Alternatively, 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 serving as the 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.

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 between the pure water flow rate measured by the pure water flow meter 42, the boric acid water flow rate measured by the boric acid water flow meter 52, and the boric acid mixed water flow rate measured by the boric acid mixed water flow meter 62.

<Abnormality determination 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.

As shown in FIG. 2 , the control device 71 compares a preset reference flow rate ratio with the actual flow rate ratio calculated from the measurement results of the flow meters 42 and 62 to determine whether an abnormality has occurred 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. A first threshold value L1 is then 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. 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 that adds 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 also be set for the first threshold value L1 without taking the margin M into account.

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. Note that 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 critical conditions of the pressurized water reactor 11.

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

As shown in Figure 3, the pressurized water reactor 11 begins startup and increases power output at time t1, begins operation at time t2 while maintaining a constant power output (Pa), reduces power output at time t3, and shuts down at time t4.

The control device 71 executes a process to determine abnormalities due to a decrease in boron concentration in the primary cooling water before and after startup of the pressurized water reactor 11.

During startup (t1-t2), the pressurized water reactor 11 undergoes core refueling, so 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 and supplies only pure water to the primary coolant circulation line 22, lowering 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 an abnormality determination by the control device 71 based on the actual flow rate ratio between the pure water flow rate and the boric acid-mixed water flow rate would be an erroneous determination. Therefore, the control device 71 does not execute the process of determining an abnormality due to a decrease in boron concentration during startup of the pressurized water reactor 11.

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, increasing 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 boron concentration in the primary cooling water at this time is normal, and while the control device 71 could perform an abnormality determination process based on the actual flow rate ratio between the pure water flow rate and the boric acid-mixed water flow rate, replenishing the primary cooling water would result in an erroneous determination. Therefore, the control device 71 does not perform a process to determine an abnormality due to a drop in boron concentration while the pressurized water reactor 11 is shut down.

Furthermore, while the pressurized water reactor 11 is in operation (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 an abnormality determination by the control device 71 based on the actual flow rate ratio between the pure water flow rate and the boric acid mixed water flow rate would be an erroneous determination. Therefore, even when the pressurized water reactor 11 is in operation, the control device 71 does not execute the process of determining an abnormality due to a decrease in boron concentration when diluting the primary cooling water for criticality control.

In other words, the control device 71 does not determine whether an abnormality due to a decrease in boron concentration in the primary system coolant exists between the start-up (t1) and shutdown (t4) of the pressurized water reactor 11.

Then, when the flow rate of pure water or boric acid mixed water fluctuates due to adjustment of the opening of each flow control valve 41, 61 before the start-up (t0-t1) and after the shutdown (t4-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 pure water to boric acid mixed water.

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

The boron concentration determination method includes the steps of measuring the first flow rate and the second flow rate of at least two of the following lines: 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, 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.

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

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 opening degrees of the flow control valves 41, 51, and 61 have been changed. If the control device 71 determines that the opening degrees of the flow control valves 41, 51, and 61 have been changed (Yes), then in step S13, the control device 71 determines whether the standby time has elapsed since the opening degrees of the flow control valves 41, 51, and 61 were changed. If the control device 71 determines that the standby time has not elapsed since the opening degrees of the flow 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 opening degrees of the flow control valves 41, 51, and 61 were changed (Yes), then the control device 71 proceeds to step S14. Furthermore, if the control device 71 determines in step S12 that the opening degrees of the flow control valves 41, 51, and 61 have not been changed (No), then the control device 71 proceeds to step S14.

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 the detection results of the flow control valves 41, 61. In step S15, the control device 71 calculates the 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 the normal range. In this case, the control device 71 determines whether the actual flow rate ratio is within the normal range using the abnormality determination map (see Figure 2) stored in the memory unit 73.

Here, 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 so the control device 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 so 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.

When the isolation valve 43 is closed, the supply of pure water to the primary system cooling water circulation line 22 through the primary system 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 system cooling water is suppressed. The pressurized water reactor 11 then shuts down.

[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.

The boron concentration determination device according to the first aspect determines abnormalities due to a decrease in boron concentration in 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, abnormalities due to fluctuations in boron concentration can be easily detected using existing equipment, minimizing the complexity and cost of the device.

The boron concentration determination device of the second aspect is the boron concentration determination device of 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 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 allows for appropriate detection of an abnormality due to fluctuations in boron concentration.

The boron concentration determination device of the third aspect is the boron concentration determination device of 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 water flow meter 52 provided in the boric acid water supply line 32; and the control device 71 determines an abnormality due to a decrease in 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 fluctuations in boron concentration.

In the boron concentration determination device of 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. The control device 71 determines an abnormality due to a decrease in boron concentration in the primary system cooling water based on the ratio of the flow rate of boric acid water measured by the boric acid water flow meter 52 to the actual flow rate of boric acid mixed water measured by the boric acid mixed water flow meter 62. This allows for appropriate detection of an abnormality due to fluctuations in boron concentration.

The boron concentration determination device according to the fifth aspect is a boron concentration determination device according to any one of the first to fourth aspects, and further includes a control device 71 that determines an abnormality due to a decrease in the boron concentration in the primary cooling water when the first flow rate or the second flow rate fluctuates, based on the actual flow rate ratio after a predetermined waiting time has elapsed. As a result, for example, when the opening of each flow control valve 41, 51, 61 is changed, causing the first flow rate or the second flow rate to fluctuate, it takes a predetermined time for this effect to appear in each flow meter 42, 52, 62. By determining an abnormality using the actual flow rate ratio after the waiting time has elapsed, highly accurate determinations can be made.

The boron concentration determination device according to the sixth aspect is the boron concentration determination device according to any one of the first to fifth aspects, and further includes a reference boron concentration in the primary cooling water for properly maintaining the pressurized water reactor 11, a reference flow rate ratio between the first flow rate and the 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 the actual flow rate ratio to determine an abnormality due to a decrease in boron concentration. This allows the flow rates measured by the flow meters 42, 52, and 62 to be directly used in determining an abnormality, simplifying the determination processing logic.

The boron concentration determination device according to the seventh aspect is the boron concentration determination device according to the sixth aspect, but further includes a normal range in which the reference boron concentration is maintained by adding a margin to the reference flow rate ratio, and the control device 71 determines an abnormality when the actual flow rate ratio is not within the normal range. This allows for factors such as equipment failures to be taken into account as a margin when determining an abnormality, thereby suppressing hunting in abnormality determinations.

The boron concentration determination device according to the eighth aspect is the boron concentration determination device according to the seventh aspect, and furthermore, the normal range can be changed depending on the critical conditions of the pressurized water reactor 11. This allows for highly accurate abnormality determination depending on the configuration of the pressurized water reactor 11, etc.

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

The boron concentration determination device according to the tenth aspect is the boron concentration determination device according to any one of the first to ninth aspects, and furthermore, 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 for appropriate determination of an abnormality due to fluctuations in boron concentration.

The boron concentration determination method according to the eleventh aspect includes the steps of measuring first and second flow rates in at least two of the primary system coolant supply line (pure water supply line) 31 that supplies pure water, the boric acid water supply line 32 that supplies boric acid water, and the boric acid mixed water supply line 33 that supplies boric acid mixed water, a mixture of pure water and boric acid water, to the primary system coolant (reactor coolant), and determining an abnormality due to a decrease in boron concentration in the primary system coolant based on the actual flow rate ratio between the first flow rate and the second flow rate. This makes it possible to easily detect abnormalities due to fluctuations in boron concentration using existing equipment, thereby preventing the device from becoming more complex and expensive.

The program according to the twelfth aspect causes a computer to execute the following steps: measuring first and second flow rates in at least two of the primary system coolant supply line (pure water supply line) 31 that supplies pure water, the boric acid water supply line 32 that supplies boric acid water, and the boric acid mixed water supply line 33 that supplies boric acid mixed water, a mixture of pure water and boric acid water, to the primary system coolant (reactor coolant); and determining whether an abnormality has occurred due to a decrease in the boron concentration in the primary system coolant based on the actual flow rate ratio between the first and second flow rates. This makes it possible to easily detect abnormalities due to fluctuations in boron concentration using existing equipment, thereby preventing the device from becoming more complex and expensive.

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 - 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. However, this configuration is not limited to this. For example, the boron concentration in the primary system coolant may be estimated based on the actual flow rate ratio of at least two flow rates - 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.

11 Pressurized water reactor 12 High temperature side supply piping 13 Low temperature side supply piping 14 Steam generator 15 Primary system cooling water pump 21 Chemical volume control system 22 Primary system cooling water circulation line 23 Volume control tank 24 Filling pump 31 Primary system cooling water replenishment line (pure water supply line)
32 Boric acid water supply line 33 Boric acid mixed water supply line 34 Mixer 41 Flow rate adjustment valve 42 Pure water flow meter 43 Isolation valve 44 Make-up water pump 45 Primary pure water tank 51 Flow rate adjustment valve 52 Boric acid water flow meter 53 Boric acid water pump 54 Boric acid water tank 61 Flow rate adjustment valve 62 Boric acid mixed water flow meter 71 Control device (determination unit)
72 Operation section 73 Storage section

Claims (12)

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