JPH0390896A - Nuclear reactor water feed controller - Google Patents

Abstract

PURPOSE:To stably control the water level in a nuclear reactor even when a main steam water feed flow rate deviation can not be used as a control signal by using pressure which varies with the heat output of the nuclear reactor as the control signal. CONSTITUTION:In the three-element control mode of a feed water flow rate, a main steam flow rate, and nuclear reactor pressure, variation in the output of the nuclear reactor 1 is detected 7 as variation in main steam flow rate to perform control for increasing or decreasing the flow rate of feed water. If a water feed flow rate detector 6 or main steam flow rate detector 7 is disabled to be used, a switch 4b is opened to perform the control, but when the heat output of the nuclear reactor 1 varies, the delay of the water level control increases. In this case, the deviation between the nuclear reactor pressure which varies with the heat output and the pressure which is inputted and held in a pressure holder 14 when a switch 4b associated with a switch 4a is opened and the compensation signal of a proportional computing element 15 based upon the deviation is added 3f to a flow rate command signal to perform control 11 over the flow rate of water fed to the nuclear reactor 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a reactor water supply control device for controlling the water level of a nuclear reactor in a boiling water nuclear power plant.

(Prior Art) A conventional nuclear reactor feed water control system for a boiling water reactor power plant is configured as shown in FIG. 3, for example.

That is, the water level of the nuclear reactor 1 is detected by the water level detector 2, and the deviation from the water level setting is calculated by the first adder/subtractor 3a. On the other hand, the feed water flow rate to the nuclear reactor 1 is detected by the feed water flow rate detector 6, and the steam flow rate from the nuclear reactor 1 is detected by the main steam flow rate detector 7. A deviation between the main steam flow rate and the feed water flow rate is taken by an adder/subtractor 3c, and a proportional calculation is performed by a proportional calculator 5 to obtain a main steam feed water deviation.

Normally, the switch 4 is turned on, and the main steam water supply deviation is added to the water level deviation by the adder/subtractor 3b to form the control deviation. Proportional calculator 8° Integral calculator 9 for control deviation.
Proportional by the differential calculator 10.

After integral and differential calculations are performed, the second adder/subtractor 3d adds them to generate a flow rate command signal. The flow rate command signal is input to the water supply pump controller 11, and the water supply pump controller 11 changes the flow rate of the water supply pump 12 according to the flow rate command signal.

Because of this configuration, if the water level in reactor 1 changes for some reason, the control deviation will change and be proportional.

The flow rate command signal generated by integral and differential calculations changes in the direction of reducing the control deviation, and the water pump controller 11
As the flow rate of the water supply pump 12 changes, the flow rate of water supplied to the nuclear reactor 1 changes, and changes in the water level of the reactor 1 are suppressed.

Further, when the thermal output of the nuclear reactor 1 changes for some reason, the main steam flow rate changes in accordance with the change in the thermal output. If the switch 4 is closed, the control deviation changes according to the change in the main steam flow rate, and the feed water flow rate changes in the same way as when the reactor water level changes. This feedwater flow rate changes in a direction consistent with the main steam flow rate.

In this way, the control action is performed before the water level in reactor 1 changes due to the mismatch between the main steam flow rate and the feed water flow rate, increasing the ability to suppress water level changes when the thermal output of reactor 1 changes. .

(Problems to be Solved by the Invention) If it becomes impossible to use the feed water flow rate detector 6 or the main steam flow rate detector 7 for some reason, the switch 4 will be opened to perform control. However, when the thermal output of the reactor 1 changes, the delay in water level control increases. In particular, when the thermal output of the nuclear reactor 1 rapidly decreases, the reduction of the water supply flow rate is delayed and the amount of rise in the water level 1 increases. This increases the possibility that an interlock that shuts down the plant will operate due to high water levels in the reactor. Therefore, there is a problem that causes a decrease in the reliability of the reactor water supply control device.

An object of the present invention is to use the reactor pressure, which changes according to the thermal output of the reactor 1, as a control signal even when the main steam feedwater flow rate deviation cannot be used as a control signal.
Another object of the present invention is to provide a reactor water supply control device that can stably control the reactor water level even when the thermal output of the reactor l changes rapidly.

[Configuration of the Invention (Means for Solving the Problems) The present invention provides a water level detector for detecting the water level of a nuclear reactor, and a first method for obtaining a water level signal from the water level detector and a deviation between the water level setting.
an adder/subtractor, a proportional calculator, an integral calculator, and a differential calculator connected to the output side of the first adder/subtracter that perform control calculations on the water level deviation; and the flow rate is calculated by summing the outputs of these calculators. a second adder/subtractor that obtains a command signal; a pressure detector that detects the pressure of the reactor; a proportional calculator that performs a control operation on the pressure signal of the pressure detector to obtain a compensation signal; and a proportional calculator that obtains a compensation signal. The nuclear reactor is characterized by having a third addition/subtraction that adds the value to the flow rate command signal, a feed water pump that supplies water to the reactor, and a feed water pump controller that changes the flow rate of the feed water pump in accordance with the flow rate command signal. do.

(Function) In the three-element control mode, changes in the reactor output are detected as changes in the main steam flow rate, and control is performed to increase or decrease the feed water flow rate. Since there is a high possibility that the main steam flow rate detector cannot be used in single-element mode, the reactor pressure signal is used as a signal to detect changes in reactor output. Proportional pressure signal,
By adding this to the output of the integral and differential calculator, changes in the furnace output can be reflected in the water supply control signal. It detects changes in reactor pressure and changes the water supply flow rate according to thermal output, making it possible to keep changes in reactor water level to a small level.

(Embodiment) An embodiment of the reactor feed water control device according to the present invention will be described with reference to FIG. 1.

In FIG. 1, a water level detector 2 and a pressure detector 13 are connected to a nuclear reactor 1. The output of the water level detector is input to the first adder/subtractor 3a together with the water level setting signal. The output side of the pressure detector 13 is connected to a signal holder 14 and an adder/subtractor 3e, and the output side of the signal holder 14 is also connected to the adder/subtractor 3e. The output side of the adder/subtractor 3e is connected to the proportional calculator 15. On the other hand, reactor 1
A water supply pipe 16 and a main steam pipe 17 are connected to the
A water supply flow rate detector 6 and a water supply pump 12 are connected to the water supply pipe 16 . A main steam flow rate detector 7 is connected to the main steam pipe 17 . The output side of the feed water flow rate detector 6 and the output side of the main steam flow rate detector 7 are connected to an adder/subtractor 3c. The output side of the adder/subtractor 3c is connected to the proportional calculator 5, and the output side of the proportional calculator 5 is connected to the first switch 4a.
It is connected to the adder/subtracter 3b together with the output side of the first adder/subtractor 3a. The first switch 4a and the second switch 4b are interlocked, and the second switch 4b is connected to the signal holder 14. The output side of the adder/subtractor 3b is branched into three parts, and a proportional calculator 8. It is connected to an integral calculator 9 and a differential calculator 1o. Proportional calculator 8. The output sides of the integral calculator 9 and the differential calculator 10 are connected to the second adder/subtractor 3.
connected to d. The output side of the second adder/subtractor 3d is connected to the output side of the proportional calculator 15 as well as the third adder/subtractor 3f.

The output side of the third adder/subtractor 3f is connected to the feed water pump controller 11, and the output side of the feed water pump controller 11 is connected to the feed water pump 12.

Next, the operation of the reactor water supply control system will be explained with reference to FIG.

The first switch 4a and the second switch 4b are interlocked, and the operation of the device differs depending on whether the t-th switch 4a and the second 4b are closed or open. A case where the switch 4a and the second switch 4b are closed will be described.

The water level in the reactor I is detected by a water level detector 2, and the deviation from the water level setting is taken by a first adder/subtractor 3a. On the other hand, the feed water flow rate to the nuclear reactor 1 is detected by the feed water flow rate detector 6, and the steam flow rate from the nuclear reactor 1 is detected by the main steam flow rate detector 7. The deviation between the main steam flow rate and the feed water flow rate is taken by an adder/subtractor 3c, and a proportional calculation is performed by a proportional calculator 5 to obtain a main steam feed water deviation. Since the first switch 4a is turned on, the main steam water supply deviation is added to the water level deviation by the adder/subtractor 3b and becomes the control deviation. Proportional calculator 8° Integral calculator 9 for control deviation. After proportional, integral, and differential calculations are performed by the differential calculator IO, the second adder/subtractor 3d adds them to generate a flow rate command signal.

On the other hand, the pressure in the nuclear reactor 1 is detected by a pressure detector 13 and input to a signal holder 14 . The signal holder 14 outputs the input signal as is if the second switch 4b is closed. When the second switch 4b is opened, the input signal at the time when the switch 4b was opened is held and outputted. Since the second switch 4b is closed, the signal holder 14 outputs the input pressure as it is, and the difference between the pressure calculated by the adder/subtractor 3e and the output of the signal holder 14 is zero. The output of the adder/subtractor 3e is subjected to a proportional calculation by the proportional calculator 15 to become a compensation signal, which is added to the flow rate command signal by the third adder/subtracter 3f. In this case, the compensation signal is 0 and no compensation will be performed.

The flow rate command signal is input to the water supply pump controller 11, and the water supply pump controller 11 changes the flow rate of the water supply pump 12 according to the flow rate command signal.

Because of this configuration, if the water level of the nuclear reactor 1 changes for some reason, the control deviation changes.

The flow rate command signal generated by proportional integral and differential calculations changes in a direction that reduces the control deviation. By changing the flow rate of the feed water pump 12 by the feed water pump controller 11, the flow rate of water supplied to the nuclear reactor 1 is changed, and a change in the water level of the reactor 1 is suppressed.

Further, if the thermal output of the nuclear reactor 1 changes for some reason, the main steam flow rate changes in accordance with the change in the thermal output. Therefore, the main steam water supply deviation occurs, the control deviation changes, the water supply flow rate changes in the same way as when the water level changes, and the deviation between the main steam flow rate and the feed water flow rate is suppressed.

In this way, since the control operation is performed before the water level changes due to the mismatch between the main steam flow rate and the feed water flow rate, the ability to suppress water level changes when the thermal output of the reactor 1 changes is enhanced.

Next, a case where the first switch 4a and the second switch 4b are open will be described. The signal holder 14 is the second
The pressure in the reactor 1 at the time the switch 4b was opened is maintained. If the thermal output of the nuclear reactor 1 changes for some reason in this state, the first switch 4a is opened. Therefore, no control action is performed in response to changes in the main steam flow rate, but the pressure changes in response to changes in heat output, and the signal holder 1
The output of the adder/subtractor 3e that calculates the difference between the output of 4 and the pressure changes. Due to this change, the compensation signal that is the output of the proportional calculator 15 changes, and is added to the flow rate command signal by the third adder/subtractor 3f, thereby changing the flow rate command signal. 1. The water supply pump 12 is operated by the water supply pump controller 11.
The flow rate of the water changes, and therefore the water supply flow rate changes.

FIG. 2 shows the simulation results when the primary coolant recirculation flow rate of the reactor 1 suddenly decreases.

Here, the first switch 4a and the second switch 4b
This assumes that it is open. In the figure, solid line A shows the response according to the present invention, and broken line B shows the response according to the prior art. The nuclear reactor 1 has a characteristic that the thermal output decreases as the primary coolant recirculation flow rate decreases. As the heat output decreases rapidly, the main steam flow rate and pressure also decrease rapidly. The water level temporarily increases due to the effect of increasing the detected water level when the primary coolant recirculation flow rate decreases, but once this effect subsides, it decreases. After this, the flow rate rises again due to the feed water flow rate being greater than the main steam flow rate. The amount of rise in the water level at this time depends on the speed at which the reactor water supply flow rate is reduced by the reactor water supply control device. In the water level response according to the present invention, the amount of rise is kept sufficiently low as shown by the solid line A, but in the case of the conventional technology, the amount of rise is large as shown by the broken line B, and the possibility of reaching the water level high trip setting increases. ing.

[Effects of the Invention] According to the present invention, it is possible to detect changes in the thermal output of a nuclear reactor as changes in pressure and to change the feed water flow rate in advance, making it possible to maintain the reactor's temperature even when there is a sudden change in thermal output. It becomes possible to suppress water level changes to a low level, and the reliability of the reactor water supply control system can be further improved.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing an embodiment of the reactor water supply control system according to the present invention, and FIG. 2 is a characteristic diagram showing simulation results when the reactor primary coolant recirculation flow rate suddenly decreases. FIG. 3 is a system diagram showing a conventional reactor water supply control system. l...Reactor 2...Water level detector 3...Adder/subtractor 4...Switch 5...Proportional calculator 6...Feed water flow rate detector 7...Main steam flow rate detector 8... ...Proportional calculator 9...Integral calculator 10...Differential calculator 11...Water pump controller 12...Water pump 13...Pressure detector 14...Signal holder 15...・Proportional calculator 16...Water supply pipe 17...Main steam pipe (8733)

Claims (1)

[Claims] A water level detector that detects the water level of the reactor, a first adder/subtractor that obtains the water level signal from the water level detector and the deviation of the water level setting, and a a proportional calculator, an integral calculator, and a differential calculator that perform control calculations, a second adder/subtractor that obtains a flow rate command signal by summing the outputs of these calculators, and a pressure detector that detects the pressure of the reactor. a proportional calculator that performs control calculations on the pressure signal of the pressure detector to obtain a compensation signal, a third adder/subtractor that adds the compensation signal to the flow rate command signal, and supplies water to the reactor. A nuclear reactor feed water control device comprising: a feed water pump that changes the flow rate of the feed water pump according to the flow rate command signal;