JPH0746158B2 - Reactor core flow measurement device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a nuclear reactor having a circulating water circulation pump inside a reactor pressure vessel, and is particularly suitable for core flow rate measurement during operation of a partial number of circulation pumps. The present invention relates to an improved core flow rate measuring device in a nuclear reactor.

[Conventional technology]

As a cooling water circulation flow rate measuring device in a reactor having a plurality of circulation pumps directly attached to the reactor pressure vessel,
The following two methods as described in JP-A-58-10692 are known.

One method is, as shown in FIG. 3, cooling water circulating through a steam-water separator 3 from a core portion 17 separated by a partition plate 2 inside a reactor pressure vessel 1. At the core support plate 18 installed at the inlet of 17 (or it is also applicable to the inlet of the fuel assembly installed at the core), a plurality of core inlet differential pressure gauges 10 Opening 15A,
15B is installed and the obtained value is input to the differential pressure flow rate converter 12. Another method is to calibrate the above method and as a back-up, in the vicinity of the inlets and outlets of the plurality of circulation pumps 4, the opening 16A of the pressure guide tube of the pump differential pressure gauge 8,
16B is installed, and the circulating flow rate of the core 17 is obtained by using this measured value and the measured value from the speedometer 7 attached to the drive motor 6. That is, the circulation pump 4 previously collects the correlation between the flow rate and the pump section differential pressure for each pump speed by a test device, and the flow rate is measured by the pump section calculator 9 from the measurement of the pump section differential pressure and the pump speed. The amount of cooling water is calculated and the total amount of the cooling water is shown in the calculator 11. Here, in the latter method of calculating the core flow rate by using the differential pressure and pump speed of the pump part, the cooling water amount can be measured because the backflow from the stopped circulation pump occurs in the partial number operation mode in which part of the circulation pump is stopped. Since it becomes difficult, the signal of the arithmetic unit 11 using the differential pressure flow rate converter 12 and the differential pressure of the pump deck part due to the differential pressure of the core support plate is conventionally used as a calibration switch.
By connecting to the operation monitoring device 14 via 13, the signal of the differential pressure flow rate converter 12 is used during normal operation, and the signal of the calculator 11 is used for this calibration and backing.

However, in the measurement of the amount of cooling water by the core inlet differential pressure gauge 10, it is difficult to directly obtain the interrelationship between the differential pressure and the flow rate by a factory test or the like, so it is necessary to calibrate in the following procedure.

FIG. 4 is a cooling water circulation flow rate calculation procedure (conventional example) when the differential pressure between the upstream side and the downstream side of the core support plate 18 is used. As shown in this figure, in order to obtain the relationship between the core support plate differential pressure and the flow rate, the total pump flow rate Q _PT is calculated, and the curve 4
According to 1, the calibration with the core support plate differential pressure ΔP _C will be performed.

Sum Q _PT pump flow rate is determined as the sum of the individual pump flow rate Q _P, individual pump flow rate Q _P is calculated by Ponpudetsuki section differential pressure [Delta] P _D and the pump rotational speed. Therefore, when the calibration curve of the differential pressure ΔP _C of the core support plate and the core flow rate Q _C is finally created, the following error factors are included.

Error of pump differential pressure gauge Error of pump rotation speed Error on pump hydraulic characteristic curve in factory test Error of core support plate differential pressure gauge Error on core support plate differential pressure and flow curve In addition to the above errors, on the display instrument There is also an error of. Therefore, the conventional cooling water circulation flow rate measuring device using the differential pressure of the core support plate has a problem in accuracy in measuring the accurate core flow rate.

In addition, even when the number of circulating pump parts is in operation such that part of the pump is stopped, the accuracy of measurement deteriorates.
Therefore, a system with improved measurement accuracy is required to replace the flow rate measuring device.

[Problems to be solved by the invention]

In a boiling water reactor, it is necessary to constantly monitor the operating state, and for this monitoring, it is necessary to accurately measure that the cooling water is sufficiently flowing into the reactor. In particular, the coolant circulation flow rate in the nuclear reactor is used as a signal related to the safety protection system, and accurate measurement is required.

Further, in a boiling water reactor in which a plurality of circulation pumps 4 are installed in the reactor pressure vessel 1, it is possible to normally perform the rated output operation even when one circulation pump 4 of all the units is stopped. Since this is possible, a normal operation state in which one pump is stopped and a partial operation is performed may occur. Therefore, the circulating flow rate must be accurately measured even in the state where the backflow is generated through the stopped circulation pump 4.

For this reason, it is difficult to directly determine the correlation between the differential pressure and the flow rate in factory tests, etc., so once determine the correlation between the pump differential pressure difference and the flow rate, and then use this correlation to determine the core support plate, etc. The method of obtaining the correlation between the differential pressure and the flow rate is not appropriate because it contains many error factors.

For this reason, a measurement system that directly uses the relationship between the differential pressure and the flow rate is necessary in a factory test or the like even when the number of circulating pumps 4 is in partial operation.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a device capable of measuring a circulating flow rate with high accuracy during operation of all cooling water circulation pumps and during operation of a single copy cooling pump. .

[Means for solving problems]

In the reactor core flow rate measuring device having a plurality of cooling water supply pumps for supplying cooling water to the reactor core in the reactor vessel, cooling water is supplied to each of the cooling water supply pumps. A pump section differential pressure gauge that detects the differential pressure between the outlet and the inlet, a speedometer that detects the rotational speed of each cooling water supply pump, and the cooling water that is determined to be operating based on the measured values of the speedometer First calculation means for calculating a forward first cooling water flow rate of the cooling water supply pump based on a detection value of the pump differential pressure gauge corresponding to the supply pump and a measurement value of the speedometer; In the cooling water supply pump from the correlation between the detected value of the pump section differential pressure gauge corresponding to the cooling water supply pump determined to be out of operation from the measured value and the previously obtained differential pressure and the reverse flow rate Second cooling in the opposite direction The provision and second calculating means for calculating an amount, and a third calculation means for calculating the core flow rate from the first coolant flow rate by subtracting the second amount of cooling water is achieved.

[Action]

Since it is determined whether the cooling water pump is “operating” or “in operation stopped” based on the rotation speed of the cooling water supply pump measured by the speedometer, this determination can be reliably performed. Moreover, since the reverse flow rate in the cooling water supply pump that is not in operation is obtained from the previously obtained correlation between the differential pressure and the reverse flow rate, this reverse flow rate is subtracted from the forward cooling water flow rate to obtain the core flow rate. , It becomes possible to obtain the core flow rate with high accuracy during the partial operation of the cooling water supply pump.

〔Example〕

First, the basic principle of the embodiment of the present invention will be described.

When one of the multiple pumps is operated and a backflow occurs in the rest of the pumps that are stopped, a differential pressure is generated in the pump deck, and the differential pressure ΔP _B is the reverse flow rate −Q _P Increase accordingly. That is, even in the reverse flow state, the relationship between the differential pressure and the reverse flow rate as shown in FIG. 5 can be obtained. Moreover, the relationship between the two can be directly obtained by a factory test or the like.

In this case, the coolant flow rate Q _C in the reactor is evaluated by the following equation.

Q _C = Q _P1 + Q _P2 ＋ …… ＋ Q _P n _1- Q _P n (However, the subscript n is the pump number, and the above formula stops the n-th circulation pump.) Therefore, when all pumps are operating, the differential pressure ΔPn caused by the forward flow of the pump deck part. Calculate the pump flow rate Q _P from
When operating the number of pump parts using the calculation of Q _C from the total of each flow rate, for the stopped pump, calculate the reverse flow rate from the differential pressure ΔP _B caused by the reverse flow of the pump deck part, and add the respective pump flow rates. The subtraction enables the coolant flow rate Q _C in the reactor pressure vessel to be accurately measured based on the direct correlation between the differential pressure and the flow rate obtained in a factory test or the like.

An embodiment of the present invention based on the above principle will be described.

An embodiment of the present invention will be described below with reference to FIG. As shown in FIG. 1, a boiling water reactor having a structure in which a cooling water circulation pump is incorporated into the reactor has a circulation pump 4 and a partition plate 2 as shown in FIG.
Is installed near the lower end of the reactor, and the drive motor 6 of the circulation pump 4 is installed at the outer bottom of the reactor pressure vessel 1 via the shaft 5. The cooling water circulates through the steam-water separator 3 from the core part 17 separated by the partition plate 2 inside the reactor pressure vessel 1, and a plurality of circulation pumps incorporated in the lower part of the reactor pressure vessel 1. The structure is such that the pressure is increased by 4 and is sent to the core part 17.

In order to measure the circulating flow rate of the cooling water, an opening 16 of the pressure guiding tube for measuring the differential pressure of the pump deck portion 21 is provided near the inlet and outlet of the plurality of circulation pumps 4. Further, the rotation speed of the circulation pump 4 is measured by a speedometer 7 attached to the pump drive motor 6.

When all circulation pumps are in operation, the core flow rate is determined by the following method and equipment. For the circulation pump 4, the correlation between the flow rate and the pump section differential pressure is evaluated in advance by a test device for each pump speed. A pump monitoring unit (I) 9 calculates the flow rate based on the measurement of the pump differential pressure and the pump speed, and the calculator 11 calculates the total amount of the cooling water. The operation monitoring device monitors the operating state of the reactor. Displayed on 14. Although two circulation pumps are shown in FIG. 4, the same applies to three or more pumps, and the number of pressure guiding tubes for measuring the pump differential pressure is not limited.

Next, during partial operation with some pumps stopped, the core flow rate is measured by the following method. The signals of the pump speedometer 7 attached to the pump driving motor 6 are displayed on the pump speed display board 19 installed on the monitoring board of the main control room. Circulation pump 4 stopped by this display board 19
After checking, switch the signal from the pump differential pressure gauge 8 and set point
22 to be transmitted to the pump unit arithmetic unit (II) 20. In the pump unit calculator (II) 20, the correlation between the pump deck differential pressure and the reverse flow rate is evaluated by a test device in advance. The backflow rate obtained by the pump computing unit (II) 20 is transmitted to the computing unit 11, and the computing unit 11 calculates the coolant flow rate by adding / subtracting the forward flow rate and the backward flow rate, and transmits it to the operation monitoring device 14. Display the flow rate.

According to the present embodiment, the correlation between the differential pressure and the flow rate directly obtained by the test device can be used in both cases of the total pump operation and the partial number operation, so that the accuracy with a small error can be obtained. It is possible to improve the coolant circulation flow rate measurement in the reactor.

Next, another embodiment of the present invention is shown in FIG. In FIG. 2, the speed signal from the pump speedometer 7 is displayed on the pump speed display panel 19 and is also input to the pump operating condition monitor 23 for judging whether the pump is operating or stopped, so that the pump is kept below the set speed. In this case, it is determined that the pump is stopped (trip), and the switching set point 22 automatically switches the pump unit computing unit 9 to the computing unit (II) 20. With this configuration, it is possible to always measure the coolant circulation flow rate accurately. However, the function to bypass the trip signal at the time of normal pump start and stop shall be provided. The above-described embodiments of FIGS. 1 and 2 only include the following error factors, excluding instrument errors.

a. When all pumps are in operation, errors in the pump differential pressure gauge, errors in pump speed, and errors on the pump hydraulic characteristic curve in factory tests.

b. During operation of the number of pump parts, the error of the pump differential pressure gauge, the error of the differential pressure in the factory test and the error on the reverse flow rate curve.

[Effects of the Invention] According to the present invention, the reverse flow rate in the cooling water supply pump determined to be in operation stop is determined from the previously obtained correlation between the differential pressure and the reverse flow rate, and the forward cooling water is obtained. Since it is subtracted from the flow rate, the core flow rate can be accurately obtained even in the partial operation of the cooling water supply pump.

[Brief description of drawings]

FIG. 1 is a control system diagram showing one embodiment of the present invention, and FIG. 2 is a control system diagram of an embodiment different from the above. FIG. 3 is a system diagram of a conventional coolant flow rate measuring device in the reactor, FIG. 4 is an explanatory diagram of the coolant flow rate measuring device in the reactor when the pressure difference of the core support plate is used, and FIG. 5 is a circulation pump. 6 is a chart showing the relationship between the flow rate and the differential pressure of the pump deck when a reverse flow is generated in the flow chart. 1 ... Reactor pressure vessel, 2 ... Partition plate, 3 ... Steam separator, 4 ... Circulation pump, 5 ... Shaft, 6 ... Drive motor, 7 ... Speedometer, 8 ... Pump deck Differential pressure gauge, 9
...... Pump calculator I, 10 ...... Reactor support plate differential pressure gauge, 11 ……
Calculator, 12 …… Differential pressure flow converter, 13 …… Calibration switch, 14
...... Operation monitoring device, 15 ...... Pressure tube for measuring differential pressure of core support plate, 16 ...... Pressure tube for measuring differential pressure of pump deck, 17 …… Speedometer, 18 …… Core support plate, 19 …… Pump speed display panel , 20 ...
… Pump calculator II, 21 …… Pump detector, 22 …… Switch setting.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP 58-129293 (JP, A) JP 58-144787 (JP, A) JP 60-213886 (JP, A) JP 60- 57291 (JP, A)

Claims (1)

[Claims] 1. A reactor core flow rate measuring apparatus having a plurality of cooling water supply pumps for supplying cooling water to a core in a reactor vessel, wherein the cooling water supply pumps cool each of the cooling water supply pumps. A pump section differential pressure gauge that detects the differential pressure at the water outlet and inlet, a speedometer that detects the rotation speed of each cooling water supply pump, and the cooling that is determined to be operating based on the measured values of the speedometer First calculating means for calculating a forward first cooling water flow rate of the cooling water supply pump based on a detection value of the pump section differential pressure gauge corresponding to the water supply pump and a measurement value of the speedometer; The cooling water supply pump from the detected value of the pump section differential pressure gauge corresponding to the cooling water supply pump determined to be in the operation stop from the measured value of and the correlation between the previously obtained differential pressure and the reverse flow rate. Second cooling water in the opposite direction A reactor core flow rate measuring device comprising: a second calculation means for calculating the amount; and a third calculation means for calculating the core flow rate by subtracting the second cooling water quantity from the first cooling water flow rate. .