JPH09113685A - Reactor scrum preventive device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for preventing reactor scrum due to total loss of feed water flow caused by low water level in secondary hot well which can immediately reduce feed water flow at the time of CPP trip. SOLUTION: When one condensate makeup system pump tripped and its backup pump did not startup, it is detected with a trip detector 28 and a recirculation flow controller 26 makes a recirculation pump 17 run back based on the trip signal from the trip detector 28. A reactor power control circuit 32 operates specific control rods based on the mismatch rate between the flowrate discharging out of the condensate makeup system and the feed water flowrate discharging out of water supply so that the reactor power decreases.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reactor scrum avoidance device applied to a boiling water nuclear power plant having a condensate purification system (side stream system).

[0002]

2. Description of the Related Art In a boiling water nuclear power plant having a condensate purification system (sidestream system), the condensate from the primary hot well of the condenser is fed through the condensate purification system to the secondary hot of the condenser. The cooling water is supplied to the wells and the cooling water is supplied from the secondary hot well to the reactor through the water supply system. This purifies the cooling water supplied to the reactor.

In a boiling water nuclear power plant equipped with a side stream type condensate purification system, the feed water supply system has two turbine-driven feed water pumps (hereinafter abbreviated as TDRFP), and the condensate purification system has 3 condensate purification system pumps (hereinafter CP
(Abbreviated as P). And during normal operation, 2
Supply water to the reactor by two TDRFPs, and 2 more
Condensate from the primary hot well of the condenser is guided to the condensate filtration desalination device by the CPP of the table and purified to be returned to the secondary hot well. That is, the cooling water to the nuclear reactor is purified by the condensate filtering and desalting device and then returned to the secondary hot well of the condenser by the two CPPs. The cooling water of the secondary hot well of this condenser supplies water to the reactor through the above-mentioned TDRFP.

At this time, if one CPP trips and the standby machine is not activated, the condensate purification system cannot maintain the rated feed water flow rate, and in this state the feed water supply system (TDR
If the FP) supplies the reactor with the rated feed water flow rate, the secondary hot well water level of the condenser will drop excessively. Therefore, in some cases, it may be possible to reach the reactor scrum due to the loss of total feedwater flow rate.

In order to avoid this, in the past, C
When one PP is tripped and the standby unit is not started, the reactor output is reduced by recirculation runback and the feedwater flow rate is narrowed down. In other words, when one of the two CPPs in the condensate purification system of a nuclear power plant trips and its spare unit is inactive, the recirculation pump is run back to reduce the reactor output and avoid the reactor scrum. I am trying to let you.

[0006]

However, at present, expansion of the operating range of boiling water reactors is being introduced, and along with this, partial power operation at low core flow rate / high reactor power is performed. However, if one CPP trips and the standby unit is not started, a recirculation runback is performed to reduce the reactor output, and the partial output operation will be limited.

Further, when the reactor output is reduced due to the recirculation runback as described above during the operation of the reactor in such an expanded operation region, the feed water flow rate of the feed water supply system is immediately increased. Since it does not decrease, the secondary hot well water level becomes low, which may lead to the reactor scrum due to the loss of the total feed water flow due to the low secondary hot well water level.

An object of the present invention is to avoid the reactor scrum in order to reduce the feed water flow rate at the time of a CPP trip at an early stage and to avoid the reactor scrum accompanying the loss of the total feed water flow due to the low secondary hot well water level. To provide a device.

[0009]

According to a first aspect of the present invention, there is provided a trip detector for detecting that one of the condensate purification system pumps has tripped and the spare unit has not started, and a trip from the trip detector. Based on the signal, a recirculation flow controller that runs back the recirculation pump, and a predetermined amount to reduce the reactor output based on the amount of mismatch between the flow rate discharged from the condensate purification system and the feed water flow rate discharged from the feed water supply And a reactor power control circuit for operating the control rods of the.

According to the first aspect of the present invention, when one of the condensate purification system pumps trips and the standby machine does not start,
Runback the recirculation pump and operate certain control rods to reduce reactor power. As a result, the decrease in reactor power is increased, and the decrease in the feedwater flow rate to the reactor is accelerated.

The invention of claim 2 is a condensate purification system pump.
A trip detector that detects that the stand trips and that the standby machine has not started, and a trip command that issues a trip command to equipment that contributes to a reduction in the feedwater flow rate to the reactor based on the trip signal from the trip detector A command device and a reactor power control circuit that operates a predetermined control rod so that the reactor power is reduced based on the amount of mismatch between the flow rate discharged from the condensate purification system and the feed water flow rate discharged from the feed water supply. ing.

According to the second aspect of the present invention, when one of the condensate purification system pumps trips and the standby machine does not start,
A trip command is issued to a device that contributes to a reduction in the flow rate of water supplied to the reactor, and a predetermined control rod is operated to reduce the reactor output. As a result, the decrease in reactor power is increased, and the decrease in the feedwater flow rate to the reactor is accelerated.

According to a third aspect of the invention, in the second aspect of the invention, the trip command device issues a trip command to the recirculation pump based on the trip signal from the trip detector.

According to the third aspect of the present invention, the recirculation pump is tripped as a device that contributes to the reduction of the feed water flow rate to the nuclear reactor. This will cause the reactor power to decrease sharply,
The feedwater flow rate to the reactor decreases faster.

According to a fourth aspect of the present invention, in the second aspect of the present invention, the trip command device issues a trip command to the recirculation pump based on the trip signal from the trip detector, and shuts down the generator load. It is the one.

According to the fourth aspect of the present invention, the recirculation pump is tripped and the generator load is cut off as a device that contributes to the reduction of the feed water flow rate to the nuclear reactor. As a result, the reactor power is rapidly reduced, and the feedwater flow rate to the reactor is reduced quickly.

According to a fifth aspect of the present invention, in the second aspect of the present invention, the trip command device issues a trip command to one operating water feed pump in the water feed system based on the trip signal from the trip detector. It was done like this.

According to the fifth aspect of the invention, as a device that contributes to a reduction in the flow rate of water supplied to the nuclear reactor, one operating water supply pump in the water supply system is tripped. As a result, the feedwater flow rate to the reactor is rapidly reduced.

The invention of claim 6 relates to a condensate purification system pump.
The trip detector detects that the stand trips and the standby unit has not started, the recirculation flow control device that runs back the recirculation pump based on the trip signal from the trip detector, and the trip detector Based on the trip command device that issues a trip command to one running water pump in the water supply system based on the trip signal, and the amount of mismatch between the flow rate discharged from the condensate purification system and the water flow rate discharged from the water supply And a reactor power control circuit for operating a predetermined control rod so as to reduce the reactor power.

According to the sixth aspect of the present invention, when one of the condensate purification system pumps trips and the standby unit does not start,
Runs back the recirculation pump and trips one operating water supply pump in the water supply system. In addition, a predetermined control rod is operated to reduce the reactor power.
As a result, the reactor power decreases sharply and the feedwater flow rate to the reactor also decreases sharply.

The invention of claim 7 is from claim 1 to claim 4.
In the invention described above, a runback command device for outputting a runback command for automatically lowering the control output of the control device of the water supply system is provided based on the trip signal from the trip detector.

According to the invention of claim 7, in addition to the effects of the inventions of claims 1 to 4, when one of the condensate purification system pumps trips and the standby machine does not start, the supply water supply system is not activated. The control output of the controller is automatically lowered. This allows
The reactor power decreases sharply, and the feedwater flow rate to the reactor also decreases sharply.

[0023]

Embodiments of the present invention will be described below. FIG. 1 is a configuration diagram showing an embodiment of the present invention. That is, it is an embodiment in which the reactor scrum avoidance device of the present invention is applied to a boiling water nuclear power plant.

First, an outline of a boiling water nuclear power plant will be described. The steam generated in the core 2 in the reactor pressure vessel 1 is supplied to the turbine 5 through the main steam pipe 3 and the steam valve 4. Further, a bypass pipe 7 is provided from the upstream side of the steam valve 4, and the above is supplied to the condenser 6 via the bypass valve 8. The bypass valve 8 is closed during normal operation.

The steam supplied to the turbine 5 is the turbine 5
Is rotated to drive the generator 9, and then condensed in the condenser 6 and accumulated in the primary hot well 12. A load 13 is connected to the generator 9 and consumes electric power from the generator 9. In addition, the water accumulated in the primary hot well 12 is
The secondary hot well of the condenser 6 is purified via a condensate purification system pipe 27 after being purified by a condensate filtration desalination device (not shown) through the three CPPs 24A, 24B, 24C of the condensate purification system. Stored in 25. This water is used as cooling water for the water supply pipe 1
0 is sent to the water supply system. The feed water supply system is composed of two TDRFPs 11A and 11B and one motor-driven feed water pump 15 (MDRFP15). During normal operation, two TDRFPs 11A and 11B feed water to the reactor pressure vessel 1. There is. The MDRFP 15 is used when the turbine 5 is started, and the flow rate adjusting valve 16 allows the feed water flow rate to be adjusted. In addition, two T of the water supply control system
The DRFP 11A, 11B, the MDRFP 15, and the flow rate control valve 16 are controlled by the control device 14.

The reactor pressure vessel 1 is provided with a recirculation pump 17 and a control rod 18 for controlling the reactor output, and a recirculation flow rate control device 26 and a control rod drive device, which are control mechanisms, respectively. It is connected to 19. The water level H in the reactor pressure vessel 1 is detected by a reactor water level gauge 20 provided in the reactor pressure vessel 1. The feed water flow rate Qw supplied to the reactor pressure vessel 1 is detected by the feed water flow meter 21, and the CPP flow rate Qcpp flowing through the condensate purification system pipe 27 is detected by the CPP flow meter 23.

Here, during normal operation of the nuclear reactor (for example, 10
At 0% rated output operation), TDRFP11
A and 11B are driven. Further, in the condensate purification system, CPPs 24A and 24B are in operation, and the rest are in standby as standby machines.

The trip detector 28 is composed of two C's in operation.
The trip signal 29 indicates that one of the PPs 24A and 24B has tripped and the standby unit has not started, and the recirculation flow rate control device 26 receives the runback signal 3
0a is output, and the output drop command 30b is output to the reactor output control circuit 32. The recirculation flow rate controller 26 receives the runback signal 30a, and then the recirculation pump 17
The control command 26a is output to.

On the other hand, the arithmetic circuit 33 calculates a flow rate deviation between the feedwater flow rate signal 31a detected by the feedwater flowmeter 21 and the CPP flowrate signal 31b detected by the CPP flowmeter 23, and outputs the mismatch signal 33a as a reactor output control. Output to the circuit 32. Based on the mismatch signal 33a, the reactor power control circuit 32 inserts the selected control rod into the control rod drive device 19, that is, the operating speed command 32a of the selected control rod and the selected control rod. The operation number command 32b is output. As a result, the control rod drive device 19 operates by selecting the control rod, determining the operation amount and the operation speed.

FIG. 2 is a block diagram of the reactor power control circuit 32. When the trip detector 28 outputs the output drop command 30b, the switches 36 and 37 are turned on, the mismatch signal 33a is taken into the reactor output control circuit 32, and the control rod operation speed adjuster 34 and the control rod operation are performed. The number adjuster 35 operates. That is, in the control rod operation speed adjuster 34, the operation speed of the control rod which is determined in advance by the magnitude of the mismatch signal 33a is selected, and the operation speed command 32a is selected.
Is output to the control rod drive device 19. Similarly, in the control rod operation number adjuster 35, a predetermined number of operation lines is selected according to the magnitude of the mismatch signal 33a and is output to the control rod drive device 19 as the operation line number command 32b. As a result, the mismatch signal 33a between the feed water flow rate signal 31a and the CPP flow rate signal 31b is eliminated early, and the reactor scrum accompanying the loss of the total feed water flow rate due to the low secondary hot well water level can be avoided.

Next, the trip command device 22 issues a trip command to a device that contributes to the reduction of the feed water flow rate to the reactor based on the trip signal 29 from the trip detector 28. The trip command device 22 performs any one of the following three operations. Which of these three operations should be performed is set in advance in the trip command device 22.

First, as a first operation, the trip command device 22 issues a trip command B1 to the recirculation pump 17 when one of the two CPPs in regular use trips and the standby machine does not start. Output. In this case, the reactor output control circuit 32 inserts the preselected control rod at the same time as the trip command B1 or with a time delay.

Next, as a second operation, the trip command device 22 outputs a trip command B1 to the recirculation pump 17 when one of the two CPPs in regular use trips and the standby machine does not start. And the load 1 of the generator 9
A generator load cutoff command B2 for cutting off No. 3 is output. In this case, the reactor power control circuit 32 inserts a preselected control rod.

The third operation is the trip command device 2
2 outputs a trip command B3 to one operating TDRFP when one of the two CPPs in regular use trips and the standby machine does not start. That is, by narrowing the flow rate of the water supply, it is possible to suppress the excessive decrease in the secondary hot well water level in the condenser 6 due to the trip of the CPP. In this case, the recirculation flow control device 26 uses the runback signal 30b.
The runback control is carried out by means of, and the reactor power control circuit 32 carries out the insertion of the preselected control rod.

Next, the runback command device 38 outputs a runback command A for automatically lowering the control output of the controller 14 of the water supply system based on the trip signal 29 from the trip detector 28. That is, regular CP
When one of the Ps trips and the standby machine does not start up, the control output of the controller 14 of the water supply control system is automatically lowered (runback) to narrow the water supply flow rate. Thereby, the CP
The excessive lowering of the secondary hot well water level in the condenser 6 due to the trip of P is suppressed.

In the above description, a boiling water reactor having a recirculation piping system is shown in which the reactor scrum avoidance device of the present invention is applied. However, a built-in core cooling water pump (internal pump) system is used. It goes without saying that it can also be applied to nuclear reactors.

[0037]

As described above, according to the present invention, CP
Since the mismatch between the CPP flow rate and the feed water flow rate caused by one trip of P can be eliminated, it is possible to avoid the reactor scrum accompanying the loss of the total feed water flow rate due to the low secondary hot well water level. Therefore, it becomes possible to contribute to the improvement of the operating rate and safety of the boiling water reactor.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a configuration diagram of a reactor output control circuit of the present invention.

[Explanation of symbols]

 1 Reactor Pressure Vessel 2 Core 3 Main Steam Pipe 4 Steam Valve 5 Turbine 6 Condenser 7 Bypass Pipe 8 Bypass Valve 9 Generator 10 Water Supply Pipe 11 TDRFP 12 Primary Hotwell 13 Load 14 Controller 15 MDRFP 16 Flow Control Valve 17 Recirculation pump 18 Control rod 19 Control rod drive device 20 Reactor water level meter 21 Feedwater flow meter 22 Trip command device 23 CPP flow meter 24 CPP 25 Secondary hot well 26 Recirculation flow controller 26a Control command 27 Condensate purification system piping 28 trip detector 29 trip signal 30a runback signal 30b output drop command 31a feed water flow signal 31b CPP flow signal 32 reactor output control circuit 33a mismatch signal 34 control rod operating speed regulator 35 control rod operating number regulator 36 switch 37 switch 38 Lamba Click command device

Claims (7)

[Claims] 1. Condensate from a primary hot well of a condenser is supplied to a secondary hot well of the condenser via a condensate purification system, and an atom is supplied from the secondary hot well via a water supply system. When one of the two condensate purification system pumps in the condensate purification system of the nuclear power plant that supplies cooling water to the reactor trips and the standby machine is not started, the recirculation pump is run. A trip for detecting that one of the condensate purification system pumps has tripped and the standby unit has not started in a reactor scrum avoidance device that is set back to reduce the reactor output and avoid the reactor scrum. A detector, a recirculation flow rate control device that runs back the recirculation pump based on a trip signal from the trip detector, a flow rate discharged from the condensate purification system, and a water supply flow discharged from the water supply supply. And a reactor output control circuit that operates a predetermined control rod so that the reactor output is reduced based on the amount of mismatch with the amount. 2. Condensate from the primary hot well of the condenser is supplied to the secondary hot well of the condenser via a condensate purification system, and the secondary hot well of the condenser is supplied with atoms via a water supply system. When one of the two condensate purification system pumps in the condensate purification system of the nuclear power plant that supplies cooling water to the reactor trips and the standby machine is not started, the recirculation pump is run. A trip for detecting that one of the condensate purification system pumps has tripped and the standby unit has not started in a reactor scrum avoidance device that is set back to reduce the reactor output and avoid the reactor scrum. A detector, a trip command device that issues a trip command to a device that contributes to the reduction of the feed water flow rate to the reactor based on a trip signal from the trip detector, and a flow rate discharged from the condensate purification system. A reactor scram avoidance device, comprising: a reactor output control circuit that operates a predetermined control rod so that the reactor output is reduced based on a mismatch amount with a feed water flow rate discharged from the feed water supply. . 3. The reactor scram avoidance according to claim 2, wherein the trip command device issues a trip command to the recirculation pump based on a trip signal from the trip detector. apparatus. 4. The trip command device, based on a trip signal from the trip detector, issues a trip command to the recirculation pump and shuts off the generator load. 2. The nuclear reactor scrum avoidance device according to 2. 5. The trip command device, based on a trip signal from the trip detector, issues a trip command to one operating water pump in the water supply system. Claims 2 to 4
Reactor scrum avoidance device according to. 6. Condensate from the primary hot well of the condenser is supplied to the secondary hot well of the condenser via a condensate purification system, and the secondary hot well of the condenser is supplied with atoms via a water supply system. When one of the two condensate purification system pumps in the condensate purification system of the nuclear power plant that supplies cooling water to the reactor trips and the standby machine is not started, the recirculation pump is run. A trip for detecting that one of the condensate purification system pumps has tripped and the standby unit has not started in a reactor scrum avoidance device that is set back to reduce the reactor output and avoid the reactor scrum. A detector, a recirculation flow control device that runs back the recirculation pump based on a trip signal from the trip detector, and a feed water supply system based on a trip signal from the trip detector. The trip command device that issues a trip command to one operating water feed pump, and the reactor output decreases based on the amount of mismatch between the flow rate discharged from the condensate purification system and the feed water flow rate discharged from the water supply And a reactor output control circuit for operating a predetermined control rod so as to operate. 7. A runback command device for outputting a runback command for automatically lowering the control output of the controller for the water supply system based on a trip signal from the trip detector is provided. The nuclear reactor scrum avoidance device according to any one of claims 1 to 4.