JPH02118495A - Reactor flow rate measuring instrument - Google Patents

Abstract

PURPOSE:To measure a core flow rate with high accuracy by calibrating a core support plate differential pressure flowmeter by a core support plate differential pressure flow rate calibrating device throughout normal operation. CONSTITUTION:Cooling water is passed through an air-water separating device 3 from a core part 17 formed by partitioning the inside of a nuclear reactor pressure vessel 1, increased in pressure by a circulation pump 4 at the lower part of the vessel 1, and then sent in the core part 17 to circulate. Then a pump differential pressure gauge 8 measures the differential pressure between the entrance and exit of the pump 4, a velocimeter 7 measures the rotating speed of the pump 4, and they are processed 9, so that the flow rate of the cooling water is indicated on a pump part differential pressure flowmeter 11. Further, a core support plate meter 10 measures the differential pressure of the core support plate and a core support plate differential pressure-flow rate computing element 12 processes the differential pressure, so that the flow rate of the cooling water is displayed on a core support plate differential pressure flowmeter 13. At this time, a differential flow rate detector 22 detects the difference between cooling flow rates indicated on the flowmeters 11 and 13 and the cooling water flow rate difference is inputted to a core support plate differential pressure flow rate calibrating device 14 to calibrate an arithmetic expression incorporated in the computing element 12. Consequently, the accuracy of the flowmeter 13 is raised to the same level of the flowmeter 11.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a nuclear reactor that has a cooling water circulation pump built into the reactor pressure vessel, and is particularly applicable to the measurement of core flow rate when a number of circulation pumps are operated. The present invention relates to a suitable nuclear reactor core flow rate measuring device.

[Conventional technology]

As a cooling water circulation flow measuring device in a nuclear reactor having a plurality of circulation pumps directly attached to the reactor pressure vessel, Japanese Patent Application Laid-Open No. 58-10692 and Japanese Patent Application Laid-Open No. 58-9289 are known.
There are the following two methods as described in Publication No. 5.

First, as shown in FIG. It can also be applied to the core support plate 18 installed in the core support plate 18 installed in the core or the inlet of the fuel assembly installed in the core, but the openings of the impulse pipes of the plurality of core inlet differential pressure gauges 10 are installed in this part. 15 is installed, and the obtained value is input to the core support plate differential pressure flow converter 12 to determine the flow rate.

The second method is a method used for calibrating the above method, in which the opening 16 of the impulse pipe of the pump differential pressure gauge 8 is installed near the inlet and outlet of a plurality of circulation pumps 4, and this measured value and the driving This is a method of determining the circulating flow rate of the reactor core 17 using the measured value from the speed meter 7 attached to the motor 6. That is,
In the circulation pump 4, the correlation between the flow rate and the differential pressure at the pump section is collected in advance for each pump speed using a test device, and the flow rate is calculated by the pump section calculator 9 from the measurement of the pump section differential pressure and pump speed. The amount of cooling water is shown to the computing device 11 as the sum of the amounts. Here, for normal operation monitoring, the latter method of determining the core flow rate using the pump section differential pressure and pump speed is not recommended.In a partial operation state where some of the circulation pumps are stopped, backflow from the stopped circulation pumps occurs. Therefore, the accuracy of cooling water amount decreases. In addition, when measuring the amount of cooling water using the former core support plate differential pressure gauge 10, it is difficult to obtain the correlation between differential pressure and flow rate through factory tests, etc., so as shown in Fig. The total sum Qpr of the pump flow rates determined by the pressure flow rate it a+lJ meter is determined and calibrated with the core support plate differential pressure ΔPc. In addition, since calibration is performed at the time of trial operation, changes in core pressure drop that occur during plant operation cannot normally be reflected, so the following errors will be included.

■Pump deck differential pressure gauge error ■Pump rotation speed change error ■Error on pump hydraulic characteristic curve in factory test ■Error in core support plate differential pressure gauge (■Change in core pressure drop over time [Problem to be solved by the invention]) In the above conventional technology, , there is a possibility that the accuracy of the core flowmeter ΔllI during pump partial number operation and W1 operation regardless of the pump rotation speed may be reduced.

An object of the present invention is to provide a high-precision core flow rate measurement method.

[Means to solve the problem]

Boiling water reactors require constant monitoring of operating conditions, and this monitoring requires accurately determining that cooling water is flowing sufficiently within the reactor. especially,
The circulating flow rate of coolant within a nuclear reactor is used as a signal related to the safety protection system, and requires highly accurate measurement.

In addition, in a boiling water reactor in which a plurality of circulation pumps 4 are installed in the reactor pressure vessel 1, rated output operation can be performed even if one or more circulation pumps 4 out of the total number stop. Since the schedule is as follows, there may be an operation state in which a partial number of pumps is operated with -1 pumps stopped.

Therefore, even when backflow is occurring through the stopped @ring pump 4, it is necessary to accurately measure the circulation flow rate.

To achieve the above objective, the pump flow rate Qp is determined by the differential pressure of the pump part, and the core flow rate is calculated as the sum of the flow rates of each pump. We will use core support plate differential pressure flow measurement to determine the core flow rate. However, this core support plate differential pressure flow measurement system is calibrated at the time of trial operation using the pump section differential pressure flow measurement system, and cannot be calibrated afterwards. Accuracy is lower than that of the differential pressure flow measurement system.

This is done by calibrating the correlation between the core support plate differential pressure and flow rate not only during test runs but also during normal operation, and by calibrating the relationship between the core support plate differential pressure and flow rate, and determining the pump part differential pressure, such as pump partial number operation and pump rotation speed imbalance operation. When the accuracy of the flow rate measurement system decreases, it can be resolved by transferring the core flow rate measurement function to the core support plate differential pressure flow rate measurement system.

[Effect]

During normal operation, by always calibrating the core support plate differential pressure flow meter using the core support plate differential pressure flow calibration device,
It is possible to improve the accuracy of core flow rate measurement. As a result, the core support plate differential pressure flowmeter can be used to accurately measure the core flow rate in place of the pump differential pressure flowmeter during operations where the accuracy of the pump differential pressure flowmeter decreases, such as when operating multiple pumps. I can do it well.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. In a boiling water reactor that has a structure in which a circulation pump for cooling water is built into the reactor, as shown in FIG. 6
is installed at the outer bottom of the reactor pressure vessel 1 via a shaft 5. Cooling water flows from the reactor core 17, which is separated from the inside of the reactor pressure vessel 1 by the partition plate 2, into steam and water molecules a.
The pressure is increased by a plurality of circulation pumps 4 installed in the lower part of the reactor pressure vessel 1, and the pressure is increased through the reactor pressure vessel 1.
Sent to 7.

In order to measure the circulating flow rate of cooling water, an opening 16 of a pressure conduit is provided near the inlets and outlets of a plurality of circulation pumps 4 to measure the differential pressure at the pump inlets and outlets. Also.

The rotation speed of the circulation pump is measured from a speed meter 7 attached to the pump drive motor 6.

During normal operation of the circulation pump, the flow rate is calculated by the pump calculator 9 using the correlation between the pump rotation speed and the differential pressure at the pump section, and the cooling water amount is calculated as the sum of the pump section differential pressure flow rate. A total of 11 are shown.

On the other hand, the differential pressure of the core support plate is
The amount of cooling water is measured by the core support plate differential pressure gauge 10, calculated by the core support plate differential pressure-flow rate calculator 12, and displayed on the core support plate differential pressure flow meter 13.

At this time, the cooling water flow rate difference △Q indicated by the pump differential pressure flowmeter 11 and the core support plate differential pressure flowmeter is detected by the differential flow rate detector 22, and this △Q is used as the core support plate differential pressure flow rate calibration. The calculation formula is input to the device 14 and is incorporated in the core support plate differential pressure-flow rate calculator 12 to calibrate it.

As a result, the accuracy of the core support plate differential pressure flow meter 13 can be made to the same level as the pump section differential pressure flow meter 11.

Next, when several pumps are operated, backflow occurs from the stopped pumps, so the measurement accuracy of the pump differential pressure flow meter 13 deteriorates. The operating state monitoring device 23 monitors such operating states.
, and the switching device 19 switches the cooling water flow conditions to be sent to the plant operation control device 20 to the signal from the core support plate differential pressure flowmeter 13. This allows the pump section differential pressure flowmeter 11 to
Even if the accuracy of the core support plate differential pressure flowmeter 12 decreases,
This makes it possible to measure the core flow rate with high accuracy.

〔Effect of the invention〕

According to the present invention, it is possible to improve the accuracy of the core support plate differential pressure flowmeter, and to improve the accuracy of the core support plate differential pressure flowmeter during operation where the accuracy of the pump section differential pressure flowmeter decreases, such as when operating a plurality of pumps. Since it can be switched to a flowmeter, the accuracy of core flow rate measurement will be improved.

[Brief explanation of drawings]

Fig. 1 is a system diagram of a reactor coolant flow measuring device according to an embodiment of the present invention, Fig. 2 is a system diagram of a conventional reactor coolant flow ffi measuring device, and Fig. 3 is a system diagram of a pump section differential pressure flow rate. FIG. 2 is an explanatory diagram of a control device and a core support plate differential pressure flow measuring device. 1...Reactor pressure vessel, 2...Partition plate, 3...Steam drain, 4...Circulation pump 55...Shirt h, 6...
・Drive motor, 7...speed meter, 8...pump differential pressure gauge. ) Me-1, / Chikuchirodome

Claims (1)

[Claims] 1. There is a difference between the reactor pressure vessel, the partition plate surrounding the reactor core in the reactor pressure vessel, the circulation pump installed at the bottom of the reactor pressure vessel, and the impulse pipe installed at the entrance and exit of the coolant. a pump section differential pressure gauge for detecting pressure, a speed meter for detecting the rotation speed of the circulation pump, a pump section differential pressure flowmeter for calculating the flow rate of the circulation pump from the pump section differential pressure gauge and the speed meter, and the core support In a core flow measuring device consisting of a core support plate differential pressure meter that detects the differential pressure between the plates and a core support plate differential pressure flowmeter that calculates the core flow rate based on the core support plate differential pressure, the signal from the pump differential pressure flowmeter is used. , a core flow rate measuring device characterized by being provided with a calibrating device for a core support plate differential pressure flowmeter. 2. In claim 1, switching from the pump differential pressure flowmeter to the core support plate differential pressure flowmeter is provided in a pump operating state in which the accuracy of core flow rate measurement by the pump differential pressure flow calculation device is reduced. A reactor core flow measurement device featuring: