JPS63277996A - Recirculation flow rate controller for nuclear reactor - Google Patents

Abstract

PURPOSE:To shorten the time when the flow rate in a furnace core decreases and to prevent the scram of a nuclear reactor by increasing the speed of an internal pump without making a start-up operation by an operator after recovery of the instantaneous service interruption of an inverter power supply. CONSTITUTION:A recirculation flow rate controller 1 outputs a command 1a for the number of revolutions of the internal pump to an automatic/manual selector 2 which outputs a power supply frequency command 4 to the inverter 3. The inverter 3 generates the AC voltage conforming to the command frequency and drives the internal pump motor. The controller sets a select switch 21 to a manual mode and rises a manual setter 22 by the pattern stored in a pattern memory device 32 when an instantaneous service interruption recovery signal 31 is inputted thereto after the instantaneous service interruption. The pump speed is thereby recovered after the recovery of the instantaneous service interruption, by which the decrease in the flow rate of the furnace core is prevented and the scram of the nuclear reactor is averted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a reactor recirculation flow rate control device for a boiling water atomic couplant used in nuclear power generation and the like.

(Prior art) Fig. 3 shows a reactor recirculation flow rate control device for a boiling water reactor using an internal pump. The null pump rotation speed command 1a is output to the automatic/manual switch 2. Further, the automatic/manual switch 2 outputs a power frequency command 4 to a variable frequency power supply device (hereinafter referred to as an inverter) 3 for driving an internal pump.

The inverter 3 receives a power supply frequency command 4, generates an alternating current voltage matching the command frequency, drives an internal pump motor 5, which is an induction motor, and drives an internal pump 6.

Note that, generally, a plurality of internal pumps 6 (about 10 units) are provided per nuclear reactor.

Further, an inverter 3, an automatic/manual switch 2, and an internal pump motor 5 are provided for each internal pump.

FIG. 4 shows the inside of the automatic/manual switching device 2 in detail. By switching the contacts 21, each internal pump can be operated in manual operation according to the output from the manual setting device 22, or again. Automatic operation can be performed in accordance with the internal pump rotation speed command 1a output from the circulation flow rate main controller 1.

Normally, when operating a nuclear reactor at power output, the contacts 21 of all automatic/manual switching devices 2 are set to automatic, and all internal pumps 6 are collectively controlled by the recirculation flow rate main controller 1 to adjust the core flow rate. do.

Also, when starting the internal pump 6, the contact 21 of the automatic/manual switch 2 connected to the internal pump 6 is set to manual, the manual setting device 22 increases the speed of the internal pump 6, and the setting device outputs 22a and the internal pump rotation speed command 1a becomes extremely small (deviation follow-up operation), the contact 21 of the automatic/manual switch 2 is set to automatic.

Therefore, when there are 10 internal pumps 6, the above operation (speed increase → deviation pursuit → automatic injection) is performed 10 times to sequentially set the automatic mode. In addition, during the above operation, the core flow rate distribution becomes non-uniform, which may cause distortion of the core power distribution, so the above operation is performed at an extremely low core flow rate (low pump rotation speed region).

(Problems to be Solved by the Invention) In a boiling water reactor having an internal pump as described above, the power input to the inverter may experience instantaneous power outages (hereinafter referred to as instantaneous power outages) due to disturbances such as lightning strikes in the power system. ), the inverter stops and power is no longer supplied to the internal pump motor. In such a case, the inertial weight of the internal pump and internal pump motor is smaller than that of a conventional recirculation pump or recirculation pump motor, so the internal pump drive flow rate and therefore the core flow rate decrease rapidly. will come.

If the above instantaneous power outage occurs when the reactor is operating at an operating point near the rated core flow rate/rated thermal output, a rapid decrease in core flow rate will occur, potentially leading to a reactor scram in the sequence shown below. There is sex.

That is, a decrease in core flow rate → a sudden increase in voids in the core → a rise in the reactor water level due to reactor water swelling → a turbine trip with a high reactor water level → a reactor scram, or a decrease in the core flow rate → a decrease in core cooling capacity → a sudden increase in MCPR → a reactor scram.

As mentioned above, a reactor scram occurs because no action can be taken to prevent a sudden decrease in core flow rate after an instantaneous power outage. That is,
After the instantaneous power outage is resolved and the inverter is restored, in order to increase the core flow rate, it is necessary to change all automatic/manual switchers that were in manual mode at the time of the inverter instantaneous trip to automatic mode before performing the operation to increase the core flow rate. There is. However, this is because the time required to place the automatic/manual switch in automatic mode is much longer than the time required for the aforementioned transient to terminate.

The present invention has been made in response to such conventional problems, and can prevent reactor scrams caused by external disturbance factors such as instantaneous power outages, and can operate boiling water reactors equipped with internal pumps. The present invention aims to provide a nuclear reactor recirculation flow rate control device that can stabilize the reactor and improve the operating rate.

(Means for Solving the Problems) That is, the present invention provides a reactor recirculation flow rate control device that adjusts the speed of a plurality of pumps arranged in a nuclear reactor and controls the recirculation flow rate. a detection means for detecting a return from a power outage; a storage means for storing a speed increase pattern for increasing the pump speed to the speed before the power outage after the instantaneous power outage is restored; The present invention is characterized by comprising a pump speed setting means for automatically changing the pump speed setting of the pump for each pump according to a pattern.

(Function) The reactor recirculation flow rate control device of the present invention includes a detection means for detecting recovery from an instantaneous power failure of the pump motor drive power source, and a memory for storing a speed-up pattern for increasing the pump speed to the speed before the power failure after the instantaneous power failure recovery. and a pump speed setting means for automatically changing the pump speed setting of the pump for each pump according to the speed increase pattern in the storage means based on the instantaneous power failure recovery detection by the detection means.

Therefore, even in the event of a momentary power failure of the inverter, the internal pump speeds up without any operation by the operator after recovery from the momentary power failure. This reduction in the core flow rate is only for a very short time, and the plant can continue operating without reaching a high reactor water level.

(Example) The details of the present invention will be described below with reference to an example shown in the drawings.

FIG. 1 shows the main parts of a nuclear reactor recirculation flow rate control device according to an embodiment of the present invention. In the figure, reference numeral 1 indicates a recirculation flow rate main controller, and internal pump rotation speed command
a is output to the automatic/manual switch 2. Further, the automatic/manual switch 2 outputs a power frequency command 4 to the inverter 3.

The inverter 3 receives a power supply frequency command 4, generates an AC voltage matching the command frequency, drives an internal pump motor (not shown), which is an induction motor, and drives an internal pump (not shown). .

In addition, multiple internal pumps (about 10 units) are generally installed per nuclear reactor, and an automatic/manual switch 2, an inverter 3, and an internal pump motor are installed for each internal pump. .

Inside the automatic/manual switch 2, there are contacts 21 and a manual setting device 22, similar to the conventional reactor recirculation flow control device described above.
is located. By switching the contact point 21, automatic operation in which the internal pump is operated according to the internal pump rotation speed command 1a output from the recirculation flow rate main controller 1, and an inter-operation operation in accordance with the output from the manual setting device 22 are performed. It is configured so that it can be switched between manual operation and manual operation of the null pump.

In addition, in the reactor recirculation flow rate control device of this embodiment, when the power outage signal 20 is ON, the manual setting device 2
At step 2, the pump speed signal 19a is input, and the automatic/manual switch 2 enters the follow-up mode, so that the output of the manual setting device 22 follows the pump speed signal 19a.

When the momentary power outage recovers, the power outage signal 20 turns OFF as shown in FIG.
4a is held ON, and the momentary power failure recovery signal 31, which is the logical product of this signal 24a and the power ON signal 25, turns the contact 21 on.
is placed in manual mode, and the pattern storage device 3 is moved toward a predetermined internal pump speed set value.
2, the output of the manual setting device 22 is automatically increased.

Note that the pattern storage device 32 outputs in time series a signal that makes the return of the pump speed after a momentary power failure optimal for the reactor core. Further, the power supply frequency command 4 is monitored so that the target pump speed almost matches the speed before the instantaneous power failure, and the pump static constant speed is set after the instantaneous power failure.

That is, in the reactor recirculation flow rate control device of this embodiment, when the instantaneous power failure recovery signal 31 is input, the changeover switch 21
is set to manual mode, and the manual setting device 22 is raised according to the pattern stored in the pattern storage device 32.

Therefore, each pump speed shows transients as shown by curves a, b, and c in Figure 2, and during a power outage, each pump coasts down separately, but after the momentary power outage recovers, the pump speed recovers and the core flow rate decreases. Prevent degradation and avoid reactor scram.

In addition, despite the instantaneous power outage, each automatic/manual switch 2 is automatically turned on while confirming that the plant is operating stably, and automatic operation, which is the control state before the instantaneous power outage, is resumed. to recover.

[Effects of the Invention] As described above, the reactor recirculation flow rate control device of the present invention can prevent reactor scrams caused by external disturbance factors such as instantaneous power outages, and can prevent boiling water installed in internal pumps from occurring. It is possible to stabilize the operation of a nuclear reactor and improve its availability.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing essential parts of an embodiment of the reactor recirculation flow rate control device of the present invention, FIG. 2 is an explanatory diagram showing the operation of the reactor recirculation flow rate control device shown in FIG. 1, and FIG. FIG. 3 is a block diagram showing the configuration of a conventional reactor recirculation flow control TLL device, and FIG. 4 is a block diagram showing essential parts of the reactor recirculation flow control device shown in FIG. 1......Recirculation flow rate main controller 1a.
...Internal pump rotation speed command 2...
・・・・・・・・・Auto/manual switch 3・・・・・・
...... Inverter 4 ...... Power frequency command 20 ...... Power outage signal 21 ... Contact 22 ... ......Manual setter 24...Time delay timer 31...
...Momentary power failure recovery signal 32 ...Pattern storage device applicant
Japan Atomic Energy Corporation Applicant Toshiba Corporation Representative Patent Attorney Sasu Suyama - Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] (1) In a reactor recirculation flow control device that controls the recirculation flow rate by adjusting the speed of a plurality of pumps arranged in a nuclear reactor, a detection means for detecting a momentary power failure recovery of a pump motor drive power source, and a momentary power failure recovery. storage means for storing a speed increase pattern for later increasing the pump speed to the speed before the power outage; and a storage means for storing a speed increase pattern for later increasing the pump speed to the speed before the power outage; 1. A nuclear reactor recirculation flow rate control device characterized by comprising: a pump speed setting means that automatically changes each time.