JP2022088947A - Flow measuring device for fast reactor and piping breakage detecting device - Google Patents

Abstract

To measure the flow rate of a primary cooling material in a tank type nuclear reactor.SOLUTION: A flow rate measuring device 100 has: a storage part 120 which stores characteristic information representing the relation between flow rates of the primary cooling material corresponding to a plurality of conduit resistance values of in-reactor piping provided in the reactor and primary currents as currents of a pump electric motor of a primary system pump when the reactor core of a fast reactor as a tank type nuclear reactor is placed in operation with a plurality of heat outputs, respectively; a current measurement part 131 which measures a current value of a current flowing to the pump electric motor; a heat output measurement part 132 which measures a heat output of the reactor core; a flow rate measurement part 133 which specifies a flow rate related to the current measured by the current measurement part 131 in the characteristic information corresponding to the heat output measured by the heat output measurement part 132 to measure a flow rate; and an output part 135 which outputs information representing the flow rate that the flow rate measurement part 133 specifies.SELECTED DRAWING: Figure 4

Description

The present invention relates to a flow rate measuring device for a fast reactor and a pipe breakage detecting device.

A tank-type nuclear reactor that houses primary equipment such as an intermediate heat exchanger, a pump, and a primary coolant (liquid sodium) in a main container is known (see, for example, Patent Document 1). In a tank-type nuclear reactor, the primary coolant is supplied to the core by driving a primary system pump to raise the temperature, and the heat between the primary coolant and the secondary coolant heated by the intermediate heat exchanger is increased. By exchanging, heat energy is transferred to the secondary coolant. The heat transferred to the secondary coolant is converted to power in the steam generator.

Japanese Unexamined Patent Publication No. 2018-194350

In a fast reactor, an electromagnetic flow meter is generally used as a flow detector for the primary coolant. By installing the electromagnetic flow meter directly in the in-core piping that connects the primary system pump and the core, the flow rate of the primary coolant flowing through the primary system pump can be measured. However, in the tank type reactor, since the piping inside the furnace is immersed in the primary coolant, it is difficult to replace the electromagnetic flowmeter, and there is a problem that the electromagnetic flowmeter cannot be installed. Therefore, it is required to measure the flow rate of the primary coolant by another method.

Therefore, the present invention has been made in view of these points, and an object of the present invention is to measure the flow rate of the primary coolant in a tank-type nuclear reactor.

The flow measuring device for a high-speed furnace according to the first aspect of the present invention is provided in a high-speed furnace which is a tank type nuclear reactor, and the primary system pump for circulating a primary cooling material flowing in the furnace of the high-speed furnace is used. It is a flow rate specifying device that specifies the flow rate of the cooling material, and when the core of the high-speed furnace is operated at each of a plurality of heat outputs, the resistance of a plurality of pipelines of the pipes in the furnace provided in the furnace. A storage unit that stores characteristic information indicating the relationship between the flow rate of the primary cooling material corresponding to each and the primary current which is the current of the pump electric motor of the primary system pump, and the current value of the current flowing into the pump electric motor. It is associated with the current measuring unit to be measured, the heat output measuring unit for measuring the heat output of the core, and the current measured by the current measuring unit in the characteristic information corresponding to the heat output measured by the heat output measuring unit. It has a flow rate measuring unit that measures the flow rate by specifying the flow rate, and an output unit that outputs information indicating the flow rate measured by the flow rate measuring unit.

The pipe breakage detecting device according to the second aspect of the present invention has the flow rate measuring device of the high-speed furnace, and in the storage unit, when the core of the high-speed furnace is operated at each of a plurality of heat outputs, The flow rate in a healthy state of the in-furnace piping and the primary current are stored in association with each other, and the flow rate in a healthy state associated with the heat output measured by the heat output measuring unit and the flow rate measurement. The unit may further have a damage detecting unit for detecting damage to the in-furnace piping based on the flow rate measured by the unit, and the output unit may output a detection result by the damage detecting unit.

When the amount of change of the current value measured by the current measuring unit per unit time is equal to or more than a predetermined amount, the flow measuring unit measures the flow rate measured immediately before over a predetermined time to obtain the measured value at the predetermined time. It may be a measured value of the flow rate.

According to the present invention, there is an effect that the flow rate of the primary coolant can be measured in the tank type nuclear reactor.

It is a figure which shows the schematic structure of the tank type nuclear reactor. It is a figure which shows the relationship between a pump flow rate and a pump head. It is a figure which shows the relationship between the primary current of a pump motor, and a pump flow rate for each reactor heat output. It is a figure which shows the structure of the flow rate measuring apparatus. It is a flowchart which shows the flow of processing in a flow rate measuring apparatus.

[Overview of the structure of the tank reactor 1]
The fast reactor flow rate measuring device 100 according to the present embodiment is a device provided in the fast reactor, which is a tank type nuclear reactor 1, and measures the flow rate of sodium as a primary coolant flowing in the fast reactor. In explaining the flow rate measuring device 100 of the fast reactor, first, the structure of the tank type nuclear reactor 1 will be described with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a tank-type reactor 1. In FIG. 1, the flow of sodium as a coolant is indicated by an arrow. Further, in the following description, the flow rate measuring device 100 of the fast reactor is simply referred to as a flow rate measuring device 100.

The tank type nuclear reactor 1 is, for example, a fast reactor. As shown in FIG. 1, a core 3, an intermediate heat exchanger 4, a primary pump 5, and an in-core pipe 6 are provided inside the main container 2 of the tank-type nuclear reactor 1. Further, the inside of the main container 2 contains sodium, which is a liquid metal as a primary coolant. Further, a pump motor 7 is connected to the primary pump 5, and an inverter 8 is connected to the pump motor 7.

The main container 2 is a container having a diameter of about 15 m to 20 m. The core 3 is horizontally supported inside the main container 2. The core 3 is provided with a core fuel containing fissile material and a control rod for controlling the core reactivity. The control rods are driven by the control rod drive mechanism. The control rod drive mechanism controls the amount of control rods inserted between the core fuels. As a result, the fission of the core fuel is controlled, and the heat output in the core 3 is controlled. The core 3 raises the temperature of sodium as a primary coolant. In the following description, sodium before the temperature rise is referred to as low temperature sodium, and sodium which has been heated to a high temperature state is also referred to as high temperature sodium.

The intermediate heat exchanger 4 has an inflow window for inflowing high-temperature sodium and an outflow window for flowing out low-temperature sodium after heat exchange. The intermediate heat exchanger 4 exchanges heat between the high-temperature sodium flowing in from the inflow window and the sodium functioning as a secondary coolant. Specifically, due to the action of the primary pump 5, high-temperature sodium whose temperature has risen to about 550 ° C. in the core 3 flows into the inlet of the intermediate heat exchanger 4. The inflowing high-temperature sodium becomes low-temperature sodium whose temperature has dropped to about 400 ° C. by heat exchange with the secondary system sodium which functions as a secondary coolant. The cold sodium flows out from the outflow window to the lower part of the main container 2. The secondary sodium flows into the steam generator 9 to heat the water and generate steam to drive the turbine.

There are a plurality of primary system pumps 5, and although not shown, they are provided on the circumference where a plurality of intermediate heat exchangers 4 are installed. The primary system pump 5 is driven by a pump motor 7 controlled by a current supplied from the inverter 8. The primary system pump 5 pumps the low-temperature sodium flowing out of the intermediate heat exchanger 4 to the in-core pipe 6. The in-core pipe 6 guides the low-temperature sodium pumped by the primary pump 5 to the core 3.

By the way, the pump flow rate, which is the flow rate of sodium discharged by the primary system pump 5, and the pump head have a relationship shown in the following equation (1). However, H is the pump head (kPa), and Q is the pump flow rate (kg / s).
H∝Q ² ... (1)

FIG. 2 is a diagram showing the relationship between the pump flow rate and the pump head. If the in-core pipe 6 is not damaged or blocked, as shown in FIG. 2, the pump head changes on the healthy pipeline resistance curve proportional to the square of the pump flow rate. Further, a characteristic curve showing the relationship between the pump flow rate and the pump head exists for each pump rotation speed of the primary system pump 5. FIG. 2 shows the rated rotation speed characteristic, 75% rotation speed characteristic, and 50%, which are characteristic curves corresponding to the rated rotation speed, the rated rotation speed of 75%, and the rated rotation speed of 50%, respectively. The rotation speed characteristics are shown. From these, the pump head and the pump rotation speed are measured, and the pump flow rate is obtained based on the relationship between the pump head and the pump flow rate in the characteristic curve corresponding to the measured pump rotation speed. Further, when the in-core pipe 6 is not damaged or blocked and the in-core pipe 6 is sound, the operating point of the primary system pump 5 corresponds to the sound pipeline resistance curve and the pump rotation speed. It is determined at the point where the characteristic curve intersects.

The pump head can be measured by providing a pressure gauge in the discharge part and the suction part of the primary system pump. However, since the pressure-sensitive part of the pressure gauge is immersed in sodium including the surroundings, it is difficult to replace the pressure gauge, and it is difficult to install the pressure gauge. Therefore, the flow rate measuring device 100 measures the flow rate by utilizing the motor current among the characteristics of the pump motor 7. Here, the primary torque component current of the pump motor 7, the torque of the pump motor 7, and the pump head have the relationship shown in the following equation (2). However, IT is the primary torque component current (A), _T is the torque (Nm) of the pump motor 7, and H is the pump head (kPa).
IT ∝ _T ∝ H ... (2)

The primary current of the pump motor 7, which is the current supplied from the inverter 8 to the pump motor 7, has the relationship shown in the following equation (3), which is the vector sum of the primary torque component current and the exciting current. However, I ₁ is the primary current (A) of the pump motor 7, and _IM is the exciting current (A) of the pump motor 7.
I ₁ ² = _IT ² + _IM ² ... (3)

From the relationship shown in the equations (2) and (3), the pump flow rate can be measured by measuring the primary current of the pump motor 7 instead of the pump head. On the other hand, the pump rotation speed of the primary system pump 5 for specifying the characteristic curve showing the relationship between the pump flow rate and the pump head can be obtained by direct measurement. However, in a high-speed furnace, in order to eliminate common factors or dependent factors at the time of loss of function, it is necessary to improve the reliability of the multiplexing system by making the measurement system with various pump rotation speeds and pump flow rates independent. It is not possible to measure the pump flow rate using the pump speed. The frequency of the power supply of the pump motor 7, which is information different from the pump rotation speed, is an approximate value of the pump rotation speed as well as being unused in the fast reactor. The frequency of the power supply of the pump motor 7 is proportional to the pump rotation speed, including the deviation due to slippage, and has the relationship shown in the following equation (4).
N∝F × (1-s) ・ ・ ・ (4)

In the formula (4), N is the pump rotation speed (min ^-1 ), F is the frequency (Hz) of the power supply of the pump motor 7, and s is the slip (no dimension) of the pump motor 7. However, when the influence of the displacement due to slippage is large, it becomes difficult to measure the pump flow rate based on the frequency of the power supply of the pump motor 7.

In a fast reactor, the flow rate of sodium as a primary coolant is set to be proportional to the reactor heat output from the partial load to the rated output operation. Therefore, the pump flow rate and the pump motor for each reactor heat output can be substituted for the characteristic curve showing the relationship between the pump flow rate and the pump lift specified for each pump rotation speed of the primary system pump 5 shown in FIG. There is a characteristic curve showing the relationship with the primary current of 7. From this, by specifying this characteristic curve in advance and measuring the reactor heat output and the primary current of the pump motor 7, the pump flow rate is determined based on the measured reactor heat output and the primary current of the pump motor 7. Can be identified.

The characteristic curve showing the relationship between the pump flow rate and the primary current of the pump motor 7 for each reactor heat output can be obtained as shown below before the reactor output operation. First, the primary system pump 5 is operated, the pump rotation speed of 0 to 100% is measured, and the relationship between the pump flow rate and the primary current of the pump motor 7 is specified. For example, when the pump rotation speed is 100%, 90%, 80%, or the like, a characteristic point showing the relationship between the pump flow rate and the primary current of the pump motor 7 is calculated. Next, the characteristic points calculated using the unique relationship of the pump rotation speed with respect to the reactor heat output when operating the pump flow rate in proportion to the reactor heat output are the pump flow rate at the reactor heat output. , Converted to a characteristic point showing the relationship with the primary current of the pump motor 7.

When calculating the characteristic curve when the reactor heat output is 100%, the primary current and pump flow rate of the pump motor 7 when the in-core piping 6 is not damaged or blocked (when sound), and when it is sound The primary current and pump flow rate of the pump motor 7 corresponding to one pipeline resistance different from the pipeline resistance of the in-core pipe 6 are measured or calculated. Then, the characteristic curve is calculated based on the relationship between the primary current and the pump flow rate at the time of sound and the relationship between the primary current and the pump flow rate different from those at the time of sound.

FIG. 3 is a diagram showing the relationship between the primary current of the pump motor 7 and the pump flow rate for each reactor heat output. In FIG. 3, the characteristic curve when the reactor heat output is 100% is shown by a thick solid line, the characteristic curve when the reactor heat output is 90% is shown by a thin solid line, and the reactor heat output is 80%. The characteristic curve at a certain time is shown by a broken line. From these characteristic curves, the pump flow rate can be obtained by measuring the reactor heat output, specifying the characteristic curve corresponding to the measured reactor heat output, and measuring the primary current of the pump electric motor 7. .. The flow rate measuring device 100 specifies the pump flow rate based on the characteristic curve for each reactor heat output shown in FIG.

Further, in FIG. 3, a curve showing the relationship between the primary current of the pump motor 7 and the pump flow rate when the in-core pipe 6 is sound is shown by a thick broken line. For example, a curve (thick broken line) showing the relationship between the primary current of the pump motor 7 when the in-furnace piping 6 is sound and the pump flow rate, and a characteristic curve (thick solid line) when the reactor heat output is 100%. The intersection with) indicates the primary current and the pump flow rate of the pump motor 7 when the in-core pipe 6 is sound and the heat output of the reactor is 100%.

As shown in FIG. 3, when the reactor heat output is 100% and the primary current of the pump motor 7 is 200 A, the pump flow rate is fixed at about 3100 kg / s and is located in the thick broken line. It can be confirmed that the pipe 6 is sound. On the other hand, if the relationship between the measured primary current of the pump motor 7 and the pump flow rate is not located on the thick broken line, there is a possibility that an abnormality such as breakage has occurred in the in-core pipe 6.

For example, when the reactor heat output is 100% and the primary current of the pump motor 7 is 150 A, the pump flow rate is specified to be about 3750 kg / s based on the characteristic curve. In this case, since the position showing the relationship between the primary current of the pump motor 7 and the pump flow rate is not on the thick broken line, it can be identified that an abnormality such as breakage has occurred in the in-core pipe 6. The flow rate measuring device 100 functions as a pipe damage detecting device and detects damage to the in-core pipe 6.

[Configuration of flow rate measuring device 100]
Subsequently, the configuration of the flow rate measuring device 100 will be described. FIG. 4 is a diagram showing the configuration of the flow rate measuring device 100 according to the present embodiment. The flow rate measuring device 100 is, for example, a computer, and has a communication unit 110, a storage unit 120, and a control unit 130. The control unit 130 includes a current measurement unit 131, a heat output measurement unit 132, a flow rate measurement unit 133, a damage detection unit 134, and an output unit 135.

The communication unit 110 is, for example, a communication interface for the flow rate measuring device 100 to communicate with other devices such as the neutron detector 10 and the ammeter 11. Here, the ammeter 11 is provided between the inverter 8 and the pump motor 7, and measures the primary current of the pump motor 7.

The storage unit 120 is, for example, a ROM (Read Only Memory), a RAM (Random Access Memory), or the like. The storage unit 120 stores various programs for operating the flow rate measuring device 100. For example, the storage unit 120 stores a program that causes the control unit 130 of the flow rate measuring device 100 to function as a current measuring unit 131, a heat output measuring unit 132, a flow rate measuring unit 133, a damage detecting unit 134, and an output unit 135.

Further, the storage unit 120 includes the flow rate of sodium (pump flow rate) corresponding to each of the plurality of pipeline resistances of the in-core pipe 6 when the core of the high-speed reactor is operated at each of the plurality of heat outputs, and the pump motor. Stores characteristic information indicating the relationship with the primary current of 7. The characteristic information is information showing characteristic curves corresponding to each of the plurality of reactor heat outputs shown in FIG. It is assumed that the storage unit 120 stores not only the characteristic information corresponding to each of the three reactor heat outputs shown in FIG. 3 but also the characteristic information corresponding to the other reactor heat outputs.

Further, the storage unit 120 stores the normal flow rate of sodium when the core of the fast reactor is operated at each of the plurality of heat outputs in association with the primary current of the pump motor 7. Specifically, the storage unit 120 stores information showing a curve showing the relationship between the primary current of the pump motor 7 and the pump flow rate when the in-core pipe 6 is sound, as shown in FIG.

The control unit 130 is, for example, a CPU (Central Processing Unit). The control unit 130 functions as a current measurement unit 131, a heat output measurement unit 132, a flow rate measurement unit 133, a damage detection unit 134, and an output unit 135 by executing an output control program stored in the storage unit 120. ..

The current measuring unit 131 measures the current value of the current flowing into the pump motor 7. For example, the current measuring unit 131 obtains current value information indicating the current value of the current flowing into the pump electric motor 7 measured by the current meter 11 provided between the pump electric motor 7 and the inverter 8. The current value of the primary current flowing through the electric motor 7 is measured.

The heat output measuring unit 132 measures the reactor heat output, which is the heat output of the core of the tank type reactor 1. For example, the heat output measuring unit 132 measures the reactor heat output by acquiring neutron flux information indicating the intensity of the neutron detected by the neutron detector 10 and converting the neutron flux information into the corresponding heat output. ..

The flow rate measuring unit 133 measures the pump flow rate by specifying the pump flow rate associated with the current measured by the current measuring unit 131 in the characteristic information corresponding to the reactor heat output measured by the heat output measuring unit 132. do. Specifically, the flow rate measuring unit 133 has characteristics corresponding to the reactor heat output measured by the heat output measuring unit 132 from the characteristic information corresponding to each of the plurality of reactor heat outputs stored in the storage unit 120. Identify the information. The flow rate measuring unit 133 measures the pump flow rate by specifying the pump flow rate associated with the current measured by the current measuring unit 131 in the selected characteristic information.

In the tank type reactor 1, the inverter 8 is provided with a spare machine, and the inverter 8 is switched to the spare machine when the regular machine fails. While the switching operation from the regular machine to the spare machine is being performed, the primary current of the pump motor 7 becomes 0. On the other hand, when the change amount of the current value measured by the current measuring unit 131 per unit time is equal to or more than the predetermined amount, the flow rate measuring unit 133 sets the measured value of the pump flow rate measured immediately before over the predetermined time to the predetermined amount. It is the measured value of the pump flow rate in time. The predetermined time is, for example, sub-seconds. By doing so, it is possible to prevent the erroneous pump flow rate from being measured when the switching operation of the inverter 8 occurs.

The damage detection unit 134 is based on the pump flow rate at the time of sound of the in-core pipe 6 associated with the reactor heat output measured by the heat output measurement unit 132 and the pump flow rate measured by the flow rate measurement unit 133. Detects damage to the inner pipe 6. Specifically, the damage detecting unit 134 has a predetermined difference between the pump flow rate at a healthy state associated with the reactor heat output measured by the heat output measuring unit 132 and the pump flow rate measured by the flow rate measuring unit 133. When the threshold value is exceeded, it is detected that the in-furnace pipe 6 is damaged.

The output unit 135 outputs information indicating the pump flow rate measured by the flow rate measuring unit 133. For example, the output unit 135 outputs information indicating the pump flow rate measured by the flow rate measuring unit 133 to a terminal (not shown) communicably connected to the flow rate measuring device 100 via the communication unit 110. Further, the output unit 135 outputs the detection result by the damage detection unit 134.

[Processing flow in the flow measuring device]
Subsequently, the flow of processing in the flow rate measuring device 100 will be described. FIG. 5 is a flowchart showing a processing flow in the flow rate measuring device 100. The flowchart shown in FIG. 5 is repeatedly executed.
First, the heat output measuring unit 132 measures the reactor heat output (S1).
Subsequently, the current measuring unit 131 measures the current value of the primary current flowing through the pump motor 7 (S2).

Subsequently, the flow rate measuring unit 133 obtains the characteristic information corresponding to the reactor heat output measured by the heat output measuring unit 132 from the characteristic information corresponding to each of the plurality of reactor heat outputs stored in the storage unit 120. Specify (S3).
Subsequently, the flow rate measuring unit 133 measures the pump flow rate by specifying the pump flow rate associated with the primary current measured by the current measuring unit 131 in the selected characteristic information (S4).

Subsequently, the flow rate measuring unit 133 determines whether or not the current value of the primary current measured in S2 has changed by a predetermined amount or more (S5). When the flow rate measuring unit 133 determines that the current value of the primary current has changed by a predetermined amount or more, the process is transferred to S7, and the flow rate measuring unit 133 determines that the current value of the primary current has not changed by a predetermined amount or more. The process is transferred to S6.

In S6, the output unit 135 outputs information indicating the pump flow rate measured by the flow rate measuring unit 133.
In S7, the output unit 135 outputs information indicating the pump flow rate measured immediately before by the flow rate measuring unit 133 for a predetermined time.

Subsequently, the damage detecting unit 134 determines whether or not the pump flow rate measured by the flow rate measuring unit 133 is different from the pump flow rate at the time of sound (S8). If the damage detection unit 134 determines that the flow rate is different from the pump flow rate in the healthy state, the process is transferred to S9, and if it is determined that the flow rate is the same as the pump flow rate in the healthy state, the process according to this flowchart is terminated.
In S9, the output unit 135 outputs the damage detection information indicating that the in-core pipe 6 is damaged.

[Effects in this embodiment]
As described above, the flow measuring device 100 according to the present embodiment has a plurality of pipelines of the in-core pipe 6 provided in the furnace when the core of the high-speed furnace is operated at each of the plurality of reactor heat outputs. Characteristic information indicating the relationship between the flow rate of sodium corresponding to each resistance and the primary current of the pump electric motor 7 is stored in the storage unit 120, and the characteristics corresponding to the reactor heat output measured by the heat output measuring unit 132. The pump flow rate is measured by specifying the pump flow rate associated with the primary current measured by the current measuring unit 131 in the information. By doing so, the flow rate of sodium in the tank reactor can be measured.

Although the present invention has been described above using the embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments, and various modifications and changes can be made within the scope of the gist thereof. All or part of the device can be functionally or physically distributed / integrated in any unit. Also included in the embodiments of the present invention are new embodiments resulting from any combination of the plurality of embodiments. The effect of the new embodiment produced by the combination has the effect of the original embodiment together.

1 Tank type reactor 2 Main container 3 Core 4 Intermediate heat exchanger 5 Primary system pump 6 In-core piping 7 Pump electric motor 8 Inverter 9 Steam generator 10 Neutral detector 11 Current meter 100 Flow measuring device 110 Communication unit 120 Storage unit 130 Control unit 131 Current measurement unit 132 Heat output measurement unit 133 Flow measurement unit 134 Damage detection unit 135 Output unit

Claims (3)

It is a flow rate specifying device for a fast reactor, which is installed in a fast reactor which is a tank type nuclear reactor and specifies the flow rate of the primary coolant by a primary pump for distributing the primary coolant flowing in the reactor of the fast reactor.
The flow rate of the primary coolant corresponding to each of the plurality of pipeline resistances of the in-core piping provided in the reactor when the core of the high-speed furnace is operated at each of the plurality of heat outputs, and the primary. A storage unit that stores characteristic information indicating the relationship with the primary current, which is the current of the pump motor of the system pump, and a storage unit that stores characteristic information.
A current measuring unit that measures the current value of the current flowing into the pump motor,
A heat output measuring unit that measures the heat output of the core,
A flow rate measuring unit that measures the flow rate by specifying a flow rate associated with the current measured by the current measuring unit in the characteristic information corresponding to the heat output measured by the heat output measuring unit.
An output unit that outputs information indicating the flow rate measured by the flow rate measuring unit, and an output unit.
A flow measuring device for a fast reactor. The fast reactor flow rate measuring device according to claim 1 is provided.
In the storage unit, when the core of the fast reactor is operated at each of a plurality of heat outputs, the flow rate at the time when the piping in the furnace is sound and the primary current are stored in association with each other.
Further, a damage detection unit that detects damage to the in-furnace piping based on the flow rate at the time of sound associated with the heat output measured by the heat output measuring unit and the flow rate measured by the flow rate measuring unit. Have and
The output unit outputs the detection result by the damage detection unit.
Piping breakage detector. When the amount of change of the current value measured by the current measuring unit per unit time is equal to or more than a predetermined amount, the flow measuring unit measures the flow rate measured immediately before over a predetermined time to obtain the measured value at the predetermined time. Measured flow rate,
The pipe damage detection device according to claim 2.

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