JPS62157598A - Controller for water level of nuclear reactor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a nuclear reactor water level control device, and particularly to a reactor water level control device suitable for application to a boiling water reactor.

(Technical background of the invention and its problems) The reactor water level in a boiling water reactor is controlled using the reactor water level signal, the feed water flow R signal, and the main steam flow rate signal. This is done by adjusting the water level and zeroing out the deviation between the actual reactor water level and the set reactor water level.

FIG. 5 is a block diagram showing a conventional reactor water level control device.

If the reactor water level signal detected by the reactor water level detector 1 is lower than the reactor water level set value stored in the reactor water level setting device 3, the deviation is adjusted by the adjustment tH! Calculated by J5. In this case, the deviation is PID system 1il
The PrD controller 7 issues a signal to increase the water flow rate to the reactor, thereby restoring the reactor water level. Further, if the actual reactor water level exceeds the reactor water level set value, the profiIrnn device 7 outputs a signal to reduce the water supply flow rate to restore the reactor water level.

Furthermore, a case will be described in which the main steam flow rate changes due to fluctuations in reactor output, for example, when the main steam flow rate decreases and settles. In this case, first, detect the main steam differential pressure.
The deviation between the main steam flow rate detected by jS9 and square root calculator 11 and the feed water flow rate detected by feed water differential pressure detector 13 and square root calculator 15 is determined by addition/subtraction calculation 2S17. Next, based on this deviation and the reactor water level from the reactor water level detector 1, a rise in the reactor water level is predicted in addition/subtraction operation t37919. After that, the predicted reactor water level and the reactor water level set value are compared in the addition/subtraction calculator 5, and the PID control u'a
The reactor water level is lowered by outputting a signal to reduce the water supply flow rate from the reactor 7. In addition, if the main steam flow rate increases and the reactor water level decreases, the opposite response to the above will be performed.
Control the reactor water level by increasing the water supply flow rate.

Here, the operation of the conventional reactor water level control system will be described in the event that the reactor output suddenly decreases, for example, one recirculation pump trips.

In this case, the reactor water level is indicated by the dashed line a in Figures 2 and 3.
As shown in Figure 2, there is an initial rise due to swelling due to the decrease in reactor pressure and core flow rate, and the reactor water level becomes higher than the reactor water level set value. Therefore, the PID controller 7 outputs a signal to reduce the water supply flow. Further, in this case, the main steam flow a decreases and becomes lower than the feed water flow rate, and a deviation occurs between the main steam flow rate and the feed water flow rate (feed water flow rate>main steam flow rate), so the adjustment calculator 17 calculates this deviation. Based on this deviation, the PIDiilltllll device 7 outputs a signal to reduce the water supply flow rate. In this way, when the feed water flow rate decreases 1' as shown by the broken line C in Figures 2 and 3, the reactor water level is suppressed as shown by the broken line a in these figures, and the reactor water level is eventually set. It settles close to the price.

Therefore, in the case of this single recirculation pump trip event, the conventional reactor water level control device suppresses the fluctuations in the reactor water level and prevents the transient fluctuations in the reactor water level from reaching the water level high trip level E. do not have. However, in an event where the reactor power fluctuates rapidly and the reactor water level fluctuates significantly, causing the reactor to scram, it may not be possible to suppress transient fluctuations in the reactor water level below the high water level trip level.

As such a case, consider, for example, an event in which a nuclear reactor scrams due to a turbine system failure. At this point, the reactor water level initially drops rapidly due to a transient increase in reactor pressure and a reactor scram.

Therefore, P[1] The controller 7 outputs a signal to increase the water supply flow rate in order to recover from this drop in the reactor water level. On the other hand, since the main steam flow ω rapidly decreases due to reactor scram, the deviation from the feed water flow rate increases (feed water flow > main steam flow rate). Therefore, the PID controller 7 outputs a signal that reduces the water supply flow rate. Therefore, normally it would be sufficient if the feed water flow rate was reduced to near zero as quickly as the main steam flow rate, but since the reactor water level drops transiently, water continues to be supplied to the reactor for a while. Eventually, as the reactor water level recovers, the water supply flow rate will be controlled to decrease rapidly. However, despite this sudden decrease in the water supply flow rate, the decreased water level may reach the water level high trip level (symbol E in FIGS. 2 and 3). The main reason for this is that advance control is not performed that takes into account the balance between reactor output and required water flow, which allows the feed water flow rate to be reduced as the reactor power decreases.

[Purpose of the invention]

This invention was made in consideration of the above facts,
In abnormal plant events where the reactor output fluctuates significantly and the reactor water level fluctuates significantly: (b) Transient fluctuations in the reactor water level can be suppressed to below the water level high trip level, improving the ability to control the reactor water level. The purpose is to provide a nuclear reactor water level control device.

[Summary of the invention]

The reactor water level control device according to the present invention predicts the reactor water level from signals of the reactor water level, feed water flow and main steam flow rate, and compares the predicted reactor water level with the reactor water level set value. In a system that determines the feed water flow and proactively controls the reactor water level, inputs the reactor output signal,
The system is configured to determine the required raw water supply water from the reactor water level, the main steam flow rate of the feed water flow R1, and the reactor output signals.

[Embodiments of the invention]

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a block diagram showing a first embodiment of a nuclear reactor water level control device according to the present invention.

The reactor water level actually measured by the reactor water level detector 21 is output to the first addition/subtraction calculator 23 . On the other hand, the feed water differential pressure is detected by the feed water differential pressure detector 25, and this feed water differential pressure is converted into the feed water flow rate by the square root calculator 27.
9. Further, the main steam differential pressure is detected by the main steam differential pressure detector 31, converted into a main steam flow rate by the square root calculator 33, and outputted to the second addition/subtractor t1 unit 29. The second addition/subtraction calculator 29 calculates the deviation (mismatch) between the feed water flow rate and the main steam flow rate, converts this deviation into a water level equivalent signal, and performs the first addition/subtraction calculation tG! ! 'Output to i23.

The first addition/subtraction sieve 23 calculates the predicted reactor water level based on the deviation of the feed water flow rate and the main steam flow rate and the nuclear reactor water level from the reactor water level detector 21, and performs a third addition/subtraction calculation N3.
Output to 5. The third addition/subtraction calculator 35 compares the reactor water level set value stored in the reactor water level setter 37 with the predicted reactor water level output from the first addition/subtraction calculator 23,
The deviation is calculated and output to the P r Dail controller 39 . The PID controller 39 determines the required water supply flow rate based on the deviation signal output from the third addition/subtraction calculator 35,
A water supply command signal is output to the fourth addition/subtraction calculator 41 in order to satisfy the required water supply flow rate.

A reactor water level signal is converted into a flow rate equivalent signal and inputted to the fourth addition/subtraction calculator 41 from the reactor water level detector 21 . Further, a reactor output signal (APRM signal) is inputted to the fourth addition/subtraction calculator 41 from the reactor output detector 43 via a filter circuit 45 . The filter circuit 45 removes the steady amplitude component of the reactor output signal to make it a stable signal, and converts it into a signal equivalent to the reactor heat output. Then, this reactor heat output equivalent signal is
The signal is converted into a flow rate equivalent signal and input to the fourth addition/subtraction calculator 41 .

Therefore, in the fourth addition/subtraction calculator 41, the PID controller 3
The reactor water level detector 21 receives the water supply command signal input from 9.
The water supply command signal is corrected by adjusting the reactor water level signal from the reactor water level signal. At the same time, the water supply command signal is also corrected by the reactor output signal from the filter circuit 45 in order to correspond to the increase/decrease in the water supply flow to the increase/decrease in the reactor output.

4th addition/subtraction operation! The water supply command signal corrected in step 41 is input to a function generator 47, 49, and is converted into a request signal to the reactor water pump for driving the turbine or the reactor water pump for driving the motor.

Next, the effect will be explained.

First, the operation in an event where the reactor output suddenly decreases, for example, when one recirculation pump trips, will be explained.

When one reactor recirculation bomb stops and the reactor output suddenly decreases as shown by solid line B in Figure 2, swelling due to the decrease in reactor pressure and core flow rate causes the solid line in Figure 2 to drop. As shown in A, the reactor water level initially rises rapidly and becomes higher than the reactor water level set value. On the other hand, when one nuclear reactor recirculation bomb stops, the main steam flow rate decreases and becomes lower than the feed water flow rate, resulting in a deviation between the main steam flow rate and the feed water flow rate (between feed water flows>main steam flow rate). This deviation is calculated by the second addition/subtraction calculator 29, and the first addition/subtraction calculator 2
3 as a signal predicting a rise in the reactor water level.

Therefore, in the first addition/subtraction calculator 23, the expected rise in water level is added to the amount of sudden rise in actual reactor water level, and a predicted signal of a large upper limit of reactor water level (predicted reactor water level signal) is obtained. The result is output to the third adder/subtractor 35. Then, the third addition/subtraction calculator 35 calculates the deviation between the reactor water level set value and the predicted reactor water level, and based on this deviation, the P/D control unit 39 adjusts the fourth
A water supply command signal is output to each addition/subtraction operation 41.

The fourth addition/subtraction calculator 41 receives a transient reactor water level signal from the reactor water level detector 21 as a signal equivalent to a misdemeanor, as well as the reactor output detector 43 and the filter circuit 4.
5, the reactor output signal is input as a flow rate equivalent signal. Since the reactor output signal is decreasing as shown by the solid line B in Figure 2, the input of this reactor output signal balances the reactor output and the required feed water flow (as the reactor output decreases, the feed water flow decreases). This will ensure a balance between the two. Therefore, the water supply command signal input from the PrD controller 39 is corrected by the fourth addition/subtraction calculator 41 in the direction of decreasing the water supply flow rate, and is output to the function generator 47.49.

When a request signal is output from the function generator 47.49 to the water supply pump, the water supply is significantly reduced as shown by the solid line C in Figure 2, and the reactor water level also decreases as shown by the solid line A in Figure 2. The water level drops significantly and then approaches the reactor water level set point.

As a result, transient fluctuations in the reactor water level can be suppressed to a sufficiently small level, and the ability to control the reactor water level can be improved.

Next, an explanation will be given of the effects of an event in which the reactor power suddenly fluctuates and the reactor water level fluctuates significantly, for example, an event in which the reactor scrams by 1° due to a turbine system failure.

Due to the transient rise in reactor pressure and reactor scram, the reactor water level initially drops rapidly, and the water level signal is used as the first addition/subtraction operation P! Output to i23. On the other hand, as the main steam flow rate rapidly decreases due to the reactor scram, the deviation between the feedwater flow rate (feedwater flow rate > main flow rate) becomes large, and this deviation becomes the first signal that predicts the reactor water level. Addition/subtraction calculator 2
Output to 3.

In the first adder/subtracter 23, the signal predicting a rise in the reactor water level from the second adder/subtracter 29 is canceled out completely or slightly by the reactor water level drop signal from the reactor water level detector 21. . A third addition/subtraction calculator 35 compares the canceled reactor water level signal and the reactor water level setting signal. As a result, the PID controller 39 outputs a water supply command signal that does not significantly change the water supply flow rate to the fourth addition/subtraction calculator 41 side. However, this fourth addition/subtraction performance is 0.
The filter circuit 4 is connected to the reactor output detector 43 to the reactor power detector 41.
A reactor output signal is inputted via step 5.

In this case, since the reactor output signal indicates that the reactor output has suddenly decreased, the fourth addition/subtraction calculator 41 captures the water supply command signal input from the PID controller 39 and The function generator 47.49 significantly reduces the signal
Output to.

Therefore, even in the event of a reactor scram due to a turbine system failure, the feed water flow rate is reduced, transient fluctuations in the reactor water level can be suppressed to a sufficiently small level, and the reactor water level can be lowered to the water level high trip level. (Symbol E in FIG. 2) The following control can be performed.

As a result, even in automatic reactor operation, the reactor water level can be made to have a margin with respect to the high water level trip level, and the safety of the reactor can be improved.

FIG. 3 is a block diagram showing a second embodiment of the reactor water level control system according to the present invention. In this second embodiment, parts similar to those in the first embodiment are designated by the same reference numerals, and a description thereof will be omitted.

The second embodiment differs from the first embodiment in that the filter circuit 45 connected to the reactor power detector 43 is
It is located at the point connected to Mix 23. In this case, the reactor output signal from the reactor output detector 43 is converted into a flow rate equivalent signal and outputted to the first adder/subtractor 23. In other words, the first adjuster 23 converts the feedwater flow J3 and main steam flow rate deviation signals from the second adjuster 29 into the reactor output signal from the reactor power detector 43. Reactor water level detector 2
Addition/subtraction to the reactor water level signal from 1. Then, the predicted water level of the reactor considering the reactor output is calculated by the first regulator 23 and output to the third regulator 35. Third addition/subtraction calculator 3
In step 5, after comparing the predicted reactor water level and the reactor water level set value, the rld controller 39 outputs a water supply command signal.

However, in this case, in order to balance the signal levels in the steady state, the reactor output signal is input to the first addition/subtraction calculator 23 as a deviation signal from the main steam flow rate signal, and the deviation in the steady state is reduced to zero. It is necessary to do so. Therefore, the gain of the main steam flow rate signal is changed.

Therefore, in this second embodiment as well, in a single reactor recirculation pump trip event, when the reactor output suddenly decreases as shown by the solid line B in FIG. can be rapidly decreased as shown by the solid line G in the figure. As a result, the reactor water level can be rapidly lowered as shown by the solid line F in Figure 4, and then stabilized at the reactor water level set value, improving the ability to control the reactor water level as in the first embodiment. can be done.

In addition, the second event in which the reactor scrams after a turbine failure is
In the case of control according to the embodiment, the predicted reactor water level signal is increased by the first addition/subtraction calculator 23 in accordance with the decrease in the reactor output, and as a result, P
A signal is output from the pump to reduce the water supply flow rate. Therefore,
Even in this event, the reactor water level can be sufficiently suppressed i+17, and transient fluctuations in the reactor water level can be controlled to below the water level high trip level (4th issue E).

〔Effect of the invention〕

As described above, the reactor water level i1++I f according to the present invention
According to the 11 device, the reactor water level is detected, the balance between the main steam flow and the feed water flow rate is considered, and the reactor output signal is input to calculate the required feed water flow rate, and the reactor water level is adjusted in advance. flJJ IlI, it is possible to reduce the feed water flow rate when the reactor power decreases, and even in the case of a plant abnormal event that involves large fluctuations in the reactor power and large fluctuations in the reactor water level. This has the effect that transient fluctuations in the reactor water level can be suppressed to below the high water level trip level, and the i, IJ all capacity of the reactor water level can be improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a first embodiment of the reactor water level control system according to the present invention, and FIG. 2 is a block diagram showing the nuclear reactor water level control device according to the present invention.
Graph showing reactor water level, reactor power and water supply flow rate, 3rd
The figure is a block diagram showing a second embodiment of the reactor water level control system according to the present invention, and FIG. 4 shows the reactor water level controlled by the second embodiment in a single reactor recirculation pump trip event, and A graph showing output and water supply flow rate, and FIG. 5 is a block diagram showing a conventional reactor water level control device. 21... Reactor output detector, 23... First addition/subtraction calculator, 25... Feed water differential pressure detector, 31... Main steam differential pressure detector, 35... Third addition/subtraction calculator , 37... Reactor water level setter, 3... P1D control, 41... 4th
Addition/subtraction calculator, 43...Reactor output detector, 45...
filter circuit.

Claims (1)

[Claims] 1. Predict the reactor water level from signals of the reactor water level, feed water flow rate, and main steam flow rate, and determine the required feed water flow rate by comparing the predicted reactor water level with the reactor water level set value. Then, the reactor output signal is input to the reactor water level control device that proactively controls the reactor water level, and the required feed water flow rate is determined from the reactor water level, feed water flow rate, main steam flow rate, and reactor output signals. A nuclear reactor water level control device characterized in that it is configured to. 2. The reactor output signal is input to correct the required water supply flow rate after determining the required water supply flow rate by comparing the reactor predicted water level and the reactor water level set value.
Nuclear reactor water level control device described in Section 1. 3. The reactor water level control system according to claim 1, wherein the reactor output signal is input as a factor for calculating the expected reactor water level, together with the signals of the reactor water level, feed water flow rate, and main steam flow rate.