JPH0659080A - Reactor core flow measuring device - Google Patents

Abstract

PURPOSE:To precisely carry out reactor core flow measuring regardless of the condition of a recirculating pump, etc., by selecting a value approximate to a rough reactor core flow rate as a reactor core total flow rate out of adding and substracting values of the loop flow rate of the A system and the B system of a jet pump. CONSTITUTION:Difference of pressure at diffuser parts of A system and B system jet pumps (10 units each) 3, 4 and the bottom part of an atomic reactor pressure vessel 1 is detected. Each differential pressure is converted to an electrical signal by flow rate transmitters 7, 8, and after it is respectively linearly corrected by square root extraction computing parts 9, 10, the total amount of 10 units for each of recirculating pumps 5, 6 of the A system and the B system is added 11, 12, this added value is detected as a signal of each of loop flow rates 13, 14 and it is transmitted to a total flow rate computing part 30. To the computing part 30, a signal of a rough reactor core flow rate 25 due to differential pressure at a lower part grid plate 22 part of a reactor core 2 and the bottom part of the vessel 1 detected by a lower part grid plate differential pressure transmitter 23 is also input. The computing part 30 computes a value most approximate to the flow rate 25 out of values (13+14, 13-14, 14-13) reciprocally adding and substracting the flow rates 13, 14 and outputs it as a reactor core total flow rate 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to measurement of a circulating flow rate of a coolant in a boiling water reactor pressure vessel, and particularly to a core capable of accurately measuring a core flow rate even when a recirculation pump is stopped. The present invention relates to a flow rate measuring device.

[0002]

2. Description of the Related Art In a reactor pressure vessel, a coolant is circulated to the core by a plurality of jet pumps installed on the outer periphery of the reactor. The plurality of jet pumps are driven by two recirculation pumps installed outside the reactor pressure vessel, and the circulating flow rate of the coolant is detected by measuring the flow rate of the jet pumps.

As shown in the system configuration diagram of FIG. 3, the conventional core flow rate measuring device is configured such that the reactor core 2 is surrounded by the reactor pressure vessel 1, and the A type jet pump 3 and the B type jet pump are provided. There are a total of 20 units, 10 for each 4 units. Corresponding to the A-system and B-system jet pumps 3 and 4, one A-system recirculation pump 5 and one B-system recirculation pump 6 drive 10 jet pumps 3 and 4, respectively. .

The core flow rate of the coolant in the core 2 is measured by detecting the pressure difference between the diffuser portions of the jet pumps 3 and 4 and the bottom portion of the reactor pressure vessel 1, and measuring the pressure difference between the jet pumps. Flow rate transmitters 7 and 8 provided for 3 and 4 respectively
Is converted into an electrical differential pressure signal by means of linear correction by the square root calculation units 9 and 10, respectively, and thereafter, for each of the A-system and B-system recirculation pumps 5 and 6 which drive the jet pumps 3 and 4. Ten
The bases are added by the adders 11 and 12, and the added value is detected as a signal of the A system loop flow rate 13 and the B system loop flow rate 14.

Furthermore, the flow rate of these two A and B loops
The core flow rate obtained by adding 13 and 14 is detected as the total core flow rate 15. The signals of the A-system and B-system loop flow rates 13 and 14 are obtained by the A-system flow indicator 16 and the B-system flow indicator 17, respectively.
The signal of the total core flow rate 15 is displayed, monitored and recorded by the recording indicator 18.

If one of the two recirculation pumps 5 and 6 is stopped, for example, the A system recirculation pump 5
When the A-type jet pump 3 is stopped, the flow rate once becomes zero in the A-type jet pump 3, but after that, due to the phenomenon of pushing of the coolant from the operating side, that is, the B-type jet pump 4, the A-type jet pump 3 is in a reverse flow state. Become.

However, in the flow rate transmitters 7 and 8 based on the differential pressure detection, the signal of the A system loop flow rate 13 is a flow rate due to the differential pressure corresponding to the reverse flow rate as in the normal flow even in such a reverse flow state. Since it is detected, the total core flow rate 15 is calculated by adding (A + B) 19, subtracting (A−B) 20, (B) depending on the operating states of the A-system and B-system recirculation pumps 5 and 6.
-A) It was necessary to switch the addition / subtraction calculation of subtraction 21.

That is, the A-system and B-system recirculation pumps 5, 6
Calculation of total core flow rate 15 when
(A + B) Addition 19 is performed. When the A-system recirculation pump 5 is stopped, (BA) subtraction 21 is switched to, and when the B-system recirculation pump 6 is stopped, (A-
B) The total core flow rate 15 was calculated by switching to subtraction 20.

It should be noted that this addition / subtraction calculation can be switched between A system and B system.
This is performed by a signal from a relay that detects the operating / stopped state of the electric motor provided in the power supply circuit of the electric motor (not shown) that drives the system recirculation pumps 5 and 6.

[0010]

In the conventional core flow rate measuring device, the operation and stop states of the recirculation pumps 5 and 6 are detected by the power supply section of the electric motor that drives the recirculation pumps 5 and 6, and the detection result is detected. Due to this, the addition / subtraction calculation 19, 20, 21 was switched immediately.

However, the actual jet pump flow rate becomes zero after a certain period of time due to the inertia of the fluid even if the recirculation pumps 5 and 6 are stopped. If the subtraction operations 20 and 21 are immediately switched to, the flow rate value due to the inertia is subtracted, so that there is a problem that the flow rate value does not match the actual core flow rate and shows a low value.

In particular, immediately after the recirculation pumps 5 and 6 are stopped, the flow rate of the jet pump on the stop side has not sufficiently decreased. Therefore, by subtracting this from the flow rate of the jet pump on the operation side, the signal of the total core flow rate of 15 is obtained. Changes to near zero and then rises as the flow rate of the jet pump on the stop side decreases.

As a countermeasure for this, there is a case where a time limit is set for the switching of the addition / subtraction calculation in anticipation of the flow rate due to inertia after the recirculation pumps 5 and 6 are stopped. It is necessary to obtain the characteristic data for lowering the flow rates of the jet pumps 3 and 4 after the pumps 5 and 6 are stopped by actual measurement in the nuclear reactor, and this work has a problem that it requires a lot of time and labor.

In actual operation, when one of the recirculation pumps 5 and 6 is stopped, as a countermeasure against this abnormality, the other recirculation pumps 5 and 6 on the operation side are manually operated to reduce the speed to reduce the core. The work to reduce the flow rate is carried out.At this time, the flow rate of the operating side jet pump decreases due to the decrease in the speed of the operating side recirculation pump. When the speed of the side recirculation pump decreases, the flow of the stop side jet pump returns from the reverse flow to the forward flow.

Therefore, at this time, if the backflow correction calculation is continued, the flow rate value for the normal flow is subtracted, and there is a problem that it does not match the actual core flow rate. Here, in particular, since this phenomenon is brought about by the manual operation of reducing the speed of the recirculation pumps 5 and 6 during operation, the time when the reverse flow returns to the normal flow and the pattern of change are always predicted and uniform. There was a peculiarity that it was not decided by.

The object of the present invention is to compare the respective core flow rates by the addition and subtraction of the A system loop flow rate and the B system loop flow rate of the jet pump with the approximate core flow rate obtained at the lower lattice plate part of the reactor pressure vessel. , It is judged that the addition / subtraction calculation approximate to the approximate core flow rate is the same as the jet pump state, and the core flow rate by this addition / subtraction calculation is selected and output as the total core flow rate,
An object of the present invention is to provide a core flow rate measuring device capable of performing accurate core flow rate measurement regardless of the states of the recirculation pump and the jet pump.

[0017]

Two recirculation pumps for forcibly circulating a coolant by driving a plurality of jet pumps installed on the outer periphery of a core in a reactor pressure vessel of a boiling water reactor. Flow rate transmitters and square root calculation units for measuring and transmitting the respective flow rates of the jet pumps, and half the plurality of jet pumps for each recirculation pump, and the square root calculation unit as the A system loop flow rate and the B system loop flow rate. In the core flow rate measuring device consisting of a flow rate adding section for adding signals from, a differential pressure transmitter and a converter for measuring the differential pressure between the lower core lattice plate section and the bottom of the reactor pressure vessel and converting it to a rough core flow rate, The core flow rate is calculated by adding and subtracting the A-system loop flow rate and the B-system loop flow rate added by the flow rate adding section to each other and the calculation result showing the minimum difference by comparing each with the rough core flow rate. Characterized by comprising a total flow rate calculation unit which selectively outputs as the core total flow.

[0018]

[Function] The signals of the respective flow rates of the A and B system jet pumps driven by the A and B system recirculation pumps are added by the A system and B system flow rate adding units, respectively, to obtain the A system loop flow rate and the B system loop flow rate. Signal. In addition to the flow rate A of the A system and the flow rate B of the B system, the approximate core flow rate C detected in the lower grid plate of the core is input to the total flow rate calculation unit, and (A + B), (AB), (BA) ) Is added and subtracted, and the following equations (1) to (3) for comparing each with the approximate core flow rate C are calculated, and which of these equations is the approximate approximation to the approximate core flow rate C. Detect if

[0019]

As a result, when the equation (1) becomes the minimum,
The flow rate obtained by the addition of (A + B) is the flow rate obtained by the subtraction of (AB) when the equation (2) is the minimum, and the flow rate obtained by the subtraction of the (BA) when the equation (3) is the minimum. Select the flow rate and output as the core flow rate.

As a result, one of the two recirculation pumps is stopped not only during the operation of the recirculation pumps, but also the A system loop flow rate and the B system loop flow rate change, the flow direction change and operation of the stop side jet pump. Even when the core flow rate changes, such as when the speed is reduced by manual operation of the side recirculation pump, the addition / subtraction calculation that matches the state of the A system and B system jet pumps is selected, and accurate core flow rate measurement is performed. it can.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. It should be noted that the same components as those of the above-described conventional technique are designated by the same reference numerals, and detailed description thereof will be omitted. As shown in the system configuration diagram of FIG. 1, a reactor pressure vessel 1 is surrounded by a core 2, and 10 A-type jet pumps 3 and 10 B-type jet pumps 4 are provided, for a total of 20 units. ing. Corresponding to the A-system and B-system jet pumps 3 and 4, each of the A-system recirculation pump 5 and the B-system recirculation pump 6 installed outside the reactor pressure vessel 1 has 10 units of the A-system. And the B system jet pumps 3 and 4 are driven.

The core flow rate is measured by detecting the pressure difference between the diffusers of the A and B system jet pumps 3 and 4 and the bottom of the reactor pressure vessel 1, and measuring the pressure difference with the flow rate transmitters 7 and 8. Is converted into an electrical differential pressure signal by means of each of the square root calculation units 9 and 10 and linearly corrected by the square root calculation units 9 and 10, respectively, and 10 units are added to each of the driven A system and B system recirculation pumps 5 and 6. , 12 are added, and the added value is detected as a signal of the A system loop flow rate 13 and the B system loop flow rate 14.

The signals of the A-system and B-system loop flow rates 13 and 14 are transmitted to the total flow rate calculation section 30 and calculated as the total flow rate calculation section 30 and output as the core total flow rate 15. The signal of the total core flow rate 15 is monitored and recorded by the indicator recorder 18. The signals of the A-system and B-system loop flow rates 13 and 14 are displayed by the A-system flow indicator 16 and the B-system flow indicator 17, respectively.

Next, a lower lattice plate differential pressure transmitter 23 for detecting the pressure in the lower core lattice plate 22 installed in the reactor pressure vessel 1 and inputting it together with the pressure in the bottom portion of the reactor pressure vessel 1 A core flow rate converter 24 is provided and its output is transmitted to the total flow rate calculation unit 30.

The lower grid plate differential pressure transmitter 23 detects the pressure difference between the core lower grid plate 22 and the bottom of the reactor pressure vessel 1 and converts this differential pressure into an electrical differential pressure signal. This differential pressure signal is further applied to the approximate core flow rate in the core flow rate converter 24.
It is configured to be converted into 25 and output the signal of the approximate core flow rate 25 to the total flow rate calculation unit 30.

Next, the operation of the above configuration will be described. The core flow rate is measured by detecting the difference in pressure between the diffuser parts of the A system and B system jet pumps 3 and 4 and the bottom part of the reactor pressure vessel 1, and measuring this difference pressure by the flow rate transmitters 7 and 8. Converted into pressure signals, each square root calculation unit 9,
After linear correction in 10, the addition units 11 and 12 add 10 units for each of the A system and B system recirculation pumps 5 and 6 that drive the jet pumps 3 and 4, and the added value is the A system. And the loop flow rate of system B 13 and 14 are detected, and the total flow rate calculation unit
Propagate to 30.

The A system and B system loop flow rates 13 and 14 are monitored by an A system flow indicator 16 and a B system flow indicator 17, respectively.
A signal of the approximate core flow rate 25 due to the differential pressure between the core lower grid plate 22 detected by the lower grid plate differential pressure transmitter 23 and the bottom of the reactor pressure vessel 1 is also separately input to the total flow rate calculation unit 30. .

The operation logic block diagram of FIG. 2 shows the operation contents of the total flow rate operation unit 30. The total flow rate operation unit 30 has an addition logic 19, subtraction logics 20, 21, 31 to 33, and an absolute signal logic.
34 to 36, a low value selection circuit 37, and changeover switches 38 to 40. The A system and B system loop flow rates 13 and 14 are added and subtracted from each other, and a separately detected rough core flow rate 25. , Calculate the following equations (1) to (3).

[0030]

The operations of the above equations (1) to (3) are performed by the addition logic 19
And subtraction logic 20, 21, 31 to 33, and absolute signal logic 34 to 36
Based on this calculation result, the minimum value approximates to the approximate core flow rate 25, and therefore, it is judged that the current operation state of the A-system and B-system jet pumps 3 and 4 is met, and the low value According to the output signal from the selection circuit 37, the corresponding switches 38, 39, 40 are closed and the switches other than the closed switches are opened.

As a result, the addition logic 19 (A system loop flow rate 13
+ B loop flow 14) and subtraction logic 20 (A loop flow)
13-B system loop flow rate 14) and one of the flow rates calculated by the subtraction logic 21 (B system loop flow rate 14-A system loop flow rate 13) is output as the core total flow rate 15 as the correct core flow rate.

That is, when the equation (1) is first discriminated from the above equations (1) to (3), both the A-system loop flow rate 13 and the B-system loop flow rate 14 are in the positive flow, and the switching is performed. Switch 38
Is turned on, and the addition logic 19 outputs a flow rate obtained by adding the A system loop flow rate 13 and the B system loop flow rate 14 as the core total flow rate 15. At this time, the changeover switches 39 and 40 are turned off.

Next, in the case of the formula (2), the A system loop flow rate 13 is a positive flow and the B system loop flow rate 14 is a reverse flow, the changeover switch 39 is turned ON, and the subtraction logic 20 causes the A system to flow. The flow rate obtained by subtracting the B system loop flow rate 14 from the loop flow rate 13 is the total core flow rate 15
Is output as. The changeover switches 38 and 40 are OFF
Has been done.

In the case of the formula (3), the B system loop flow rate is 14
Is the normal flow, the A system loop flow rate 13 is in the reverse flow state, the changeover switch 40 is turned ON, and the subtraction logic 21 causes the B system loop flow rate 14
The flow rate obtained by subtracting the A system loop flow rate 13 from is output as the total core flow rate 15. At this time, the changeover switches 38 and 39 are turned off. The total core flow rate of 15 determined as above is recorded by the indicator.
It is transmitted to 18 and recorded and instructed.

During the reactor operation, the addition logic 19 and the subtraction logics 20 and 21 (A system loop flow rate 13 + B system loop flow rate 14), (A system loop flow rate 13-B system loop flow rate 14), respectively,
(B system loop flow rate 14-A system loop flow rate 13) is performed, and when the A system or B system recirculation pumps 5, 6 are stopped, the A system and B system jet pumps 3, 4 From the system loop flow rates 13 and 14, the flow rates in the A and B system jet pumps 3 and 4 and the forward and reverse directions are discriminated, and A
The core flow rate corresponding to the states of the system and B system jet pumps 3 and 4 is selected and output as the total core flow rate 15.

For example, assuming that the A-system recirculation pump 5 is stopped, immediately after the A-system recirculation pump 5 is stopped, the flow rate of the A-side jet pump 3 on the stop side is not sufficiently reduced due to inertia. Addition logic 19 (A system loop flow rate 13+
Since the difference between the flow rate value due to the B system loop flow rate 14) and the approximate core flow rate 25 is small, the low value selection circuit 37 is the same as when the two A system and B system recirculation pumps 5 and 6 were operating. To
The changeover switch 38 is turned on, and the core flow rate (A system loop flow rate 13 + B system loop flow rate 14) from the addition logic 19 is selected.
Therefore, the phenomenon that the signal of the total core flow rate 15 at the time of switching is largely changed does not occur.

At this time, the flow rate value by the subtraction logic 20 is (A
System loop flow rate 13-B system loop flow rate 14) and subtraction logic
The flow rate value according to 21 is (B system loop flow rate 14-A system loop flow rate
13), both of which are significantly small, and therefore the difference from the approximate core flow rate 25, which is still close to the rated flow rate, is large.

Next, as the flow rate of the A side jet pump 3 on the stop side decreases, a backflow flows from the B type jet pump 4. The core flow rate at this time decreases because the flow rate of the A system jet pump 3 is subtracted from the flow rate of the B system jet pump 4, and the approximate core flow rate 25 also decreases. At this point,
Since the addition flow 19 adds the backflow of the A system jet pump 3 to the flow rate of the B system jet pump 4, the difference between this flow rate value and the approximate core flow rate 25 becomes large.

On the other hand, the subtraction logic 20 (A system loop flow rate 13
In the −B system loop flow rate 14), the flow rate of the operating side B system jet pump 4 is subtracted from the backflow amount of the A system jet pump 3, so that the flow rate value becomes large. However, the subtraction logic 21 (B system loop flow rate 14-A system loop flow rate 13)
Then, since the calculation that matches the current situation, that is, the reverse flow amount of the A system jet pump 3 is subtracted from the flow rate of the operating side B system jet pump 4, the difference between the flow rate value and the approximate core flow rate 25 is small.

Therefore, the low value selection circuit 37 turns on the changeover switch 40 and turns off the changeover switches 38 and 39 to select the core flow rate from the subtraction logic 21 close to the approximate core flow rate 25,
The correct core flow rate in consideration of the backflow state in the A side jet pump 3 on the stop side is output as the total core flow rate 15.

Furthermore, when the flow rate of the operating side B-system jet pump 4 is reduced and the stopping side A-type jet pump 3 is not pushed, the flow direction of the A-side jet pump 3 is changed from the reverse flow to the forward flow. The core flow rate is different from that in the reverse flow, and the flow rate of the A system jet pump 3 is added to the flow rate of the operating side B system jet pump 4. Therefore, in the state of the subtraction logic 21 (B system loop flow rate 14-A system loop flow rate 13), a large difference occurs in comparison with the approximate core flow rate 25.

In addition, the subtraction logic 20 also shows that (A system loop flow rate 13
The difference from the approximate core flow rate 25 is large because the B system loop flow rate 14) is subtracted. However, the flow rate value by the addition logic 19 is (A system loop flow rate 13-B system loop flow rate 14)
Then, the flow rate of the B system jet pump 4 and the positive flow of the A system jet pump 3 are added to obtain the A system and B system jet pumps 3,
The flow rate value and the approximate core flow rate are calculated in accordance with the state of 4
Since the difference from 25 is small, the low value selection circuit 37 turns on the changeover switch 38, turns off the changeover switches 39 and 40, and outputs the core flow rate by the addition logic 19 as the total core flow rate 15.

As described above, the A and B system recirculation pumps 5, 6
Of the A system and B system recirculation pumps 5 and 6 suddenly stopped, as well as the normal operation of the two system Flow condition, and the total flow rate calculation always responding to the status change in the A system and B system jet pumps 3 and 4 even when the speed is reduced by manually operating the normal side recirculation pump in response to this abnormality. The unit 30 can measure an accurate core flow rate by selecting an appropriate addition / subtraction logic and core flow rate.

[0045]

As described above, according to the present invention, no matter how the operating states of the two recirculation pumps in the boiling water nuclear power plant change, the reactor pressure by the plurality of jet pumps driven by the pumps can be changed. Since the core flow rate in the vessel can be accurately monitored and grasped, there is an effect that reliability and safety of operation of the nuclear power plant are improved.

[Brief description of drawings]

FIG. 1 is a system configuration diagram of a core flow rate measuring device according to an embodiment of the present invention.

FIG. 2 is a calculation logic block diagram of a total flow rate calculation unit according to an embodiment of the present invention.

FIG. 3 is a system configuration diagram of a conventional core flow rate measuring device.

[Explanation of symbols]

1 ... Reactor pressure vessel, 2 ... Reactor core, 3 ... A system jet pump, 4 ... B system jet pump, 5 ... A system recirculation pump,
6 ... B system recirculation pump, 7, 8 ... Flow rate transmitter, 9, 10 ...
Square root calculation unit, 11, 12 ... Addition unit, 13 ... A system loop flow rate, 14
... B system loop flow rate, 15 ... Core flow rate, 16 ... A system flow rate indicator, 17 ... B system flow rate indicator, 18 ... Recording indicator, 19 ... Addition logic, 20, 21, 31-33 ... Subtraction logic, 22 ... Lower core lattice plate,
23 ... Lower grid plate differential pressure transmitter, 24 ... Core flow converter, 25 ...
Approximate core flow rate, 30 ... Total flow rate calculation section, 34-36 ... Absolute signal logic, 37 ... Low value selection circuit, 38-40 ... Changeover switch.

Claims (1)

[Claims] 1. A pair of recirculation pumps for forcibly circulating a coolant by driving a plurality of jet pumps installed on the outer periphery of a core in a reactor pressure vessel of a boiling water reactor, and the plurality of jet pumps. Half of the plurality of jet pumps for each recirculation pump and a flow rate transmitter and square root calculation unit for measuring and transmitting each flow rate are divided into A system loop flow rate and B
In the core flow rate measuring device consisting of a flow rate addition section that adds the signal from the square root calculation section as a system loop flow rate, the difference that measures the differential pressure between the lower grid plate section of the core and the bottom of the reactor pressure vessel and converts it into a rough core flow rate The core transmitters are calculated by adding and subtracting the pressure transmitter and the converter and the A-system loop flow and the B-system loop flow added by the flow adder to each other and compare each with the rough core flow. A core flow rate measuring device comprising a total flow rate calculation unit for selectively outputting a calculation result having a minimum difference as a core total flow rate.