JP2645188B2 - Recirculation pump stop detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the monitoring of the operation of a coolant recirculation pump in a boiling water reactor, and more particularly, to the detection of a stop in the operation control of a reactor.

[0002]

2. Description of the Related Art Generally, the output of a boiling water reactor is adjusted by changing the recirculation flow rate of coolant and by inserting control rods. As for the recirculation pump and its power supply, as shown in the recirculation pump drive system diagram of FIG. 3, a recirculation pump 1 for controlling the recirculation flow rate and a drive motor 2 directly connected to the recirculation pump 1 3
A power source for driving the drive motor 2 is provided outside the reactor containment vessel 3 and is supplied with power from a high-voltage bus 4 in the power plant, and a transmission mechanism 6 connected to the motor 5. A power supply 8 composed of a variable-speed generator 7 supplies power from the power supply 8 to the drive motor 2 via an electric circuit 11 via a circuit breaker 9 and a reactor containment penetration 10 penetrating the reactor containment 3. Supplied.

[0003] However, since the recirculation pump 1 and the drive motor 2 are installed in the reactor containment vessel 3, their operating conditions cannot be directly monitored. For this reason, conventionally, a flow detector 13 is installed in the pipe 12 of the recirculation pump 1 to monitor the operation and stoppage indirectly based on the recirculation flow rate and the like.

[0004]

If the recirculation pump 1 stops for some reason during the operation of the reactor, the recirculation flow rate decreases and the operation of the reactor becomes unstable. In this case, a selective control rod insertion control is performed in order to detect a decrease in the operating state of the reactor and the recirculation flow rate and to suppress the reactor output. However, in the case of a low recirculation flow rate operation due to the low output of the reactor or the insertion position of the control rod, even if one recirculation pump 1 is stopped, the stop information of the recirculation pump 1 due to a change in the recirculation flow rate is obtained. However, there is a problem in that the signal is easily affected by the instrument sensitivity, background noise, and the like, and thus the reliability is poor.

That is, when the stoppage of the recirculation pump 1 is detected by the recirculation flow signal, the flow rate due to the natural circulation of the coolant is also detected, and this is the background noise of the stop detection signal. Even though one pump 1 has stopped, there is a possibility that the stop detection signal is not output.

An object of the present invention is to detect the presence or absence of a power supply for driving a recirculation pump, and to use this as a stop signal for the recirculation pump via a logic circuit to obtain a highly reliable signal including the state of a detection instrument and the like. An object of the present invention is to provide a recirculation pump stop detection device for obtaining monitoring information.

[0007]

A plurality of detecting means installed on an electric circuit of a drive motor for driving a recirculation pump and detecting that voltages or currents having different phases applied to the drive motor have dropped below predetermined values, respectively. A stop detection circuit is provided for outputting a stop signal for the recirculation pump when the signals output from the plurality of detection means are input together.

[0008]

The detection means detects that the voltages or currents having different phases applied to the drive motor of the recirculation pump have fallen below predetermined values, and these signals are formed in the stop detection circuit by the logic circuit having the same phase. At least 1
When one or more signals output from different phases are both output, it is determined that the power to the drive motor has been lost and the recirculation pump has stopped, and a stop signal for the recirculation pump is output. Further, various conditions are combined with the stop signal of the recirculation pump to form a control signal for the nuclear reactor.

[0009]

An embodiment of the present invention will be described with reference to the drawings. The drawing shows only one of two recirculation systems normally installed in a boiling water reactor for convenience of explanation, and shows a case where the system is adopted in a selective control rod insertion system.
As shown in the configuration diagram of the recirculation pump stop detection device in FIG. 1, the power supply device 8 of the recirculation pump 1 and the drive motor 2 includes a motor 5, a transmission mechanism 6 and a variable speed generator 7 connected thereto.
The three-phase output of the variable speed generator 7 is connected to the recirculation pump 1 by the electric circuit 11 via the reactor containment penetration 10 penetrating the reactor containment vessel 3 shown in FIG. Is supplied to the drive motor 2.

As the stop detecting device 14, on the output side of the circuit breaker 9, instrument transformers 15 and 16 as voltage detecting means are connected between two different phases (between lines) of the three phases. Two undervoltage relays 17a, 17b, 1 on the output side
8a and 18b are connected and multiplexed. Further, the outputs of the undervoltage relays 17a, 17b, 18a, 18b are input to a stop detection circuit 19,
Are the first OR circuits 20a, 20b, 20c, 20d and the first AND circuits 21a, 21b, 21c, 21d, the second OR circuits 22a, 22b, and the second AND circuit 23
It is composed of

The undervoltage relays 17a, 17b and 18
a and 18b are output from the first O of the stop detection circuit 19, respectively.
It is input to one input terminal of the R circuits 20a, 20b, 20c, 20d. Further, the first OR circuits 20a, 20a
b, 20c and 20d are output to the first AND circuit 21
a, 21b, 21c, and 21d are input to one of the input terminals, and the outputs of the first AND circuits 21a and 21b are connected to the input terminal of the second OR circuit 22a and to the first AND circuit 21c. The output of 21d is the second OR circuit 2
2b, and the second OR circuit 22
The outputs of a and 22b are input to the input terminal of the second AND circuit 23. The output signal S23 of the stop detection circuit 19, which is the output of the second AND circuit 23, is a selection control rod insertion signal in this case.

As another component, the recirculation pump 1
The flow rate detector 12 provided on the discharge side of the sensor and the flow rate signal and the nuclear instrumentation signal 24 are inputted, and the selection control rod is connected to the other input terminals of the first AND circuits 21a, 21b, 21c and 21d of the stop detection circuit 19. Area signals S25a, S25b, S25
A nuclear instrument panel 25 for outputting c and S25d is provided.
The first OR circuit 20 in the stop detection circuit 19
Outputs from undervoltage relays of another recirculation system of the same reactor (not shown) are input to the other input terminals of a, 20b, 20c, and 20d.

Next, the operation of the above configuration will be described. Here, if the voltage between the two phases (between the lines) to which the instrument transformer 15 is connected drops for some reason, the output voltage of the instrument transformer 15 also drops. This voltage drop is detected by the two undervoltage relays 17a and 17b connected to the instrument transformer 15, and when the voltage drop becomes equal to or less than the set value, the undervoltage signals S17a and S17, respectively.
b is emitted. These undervoltage signals S17a and S17b
Are the first OR circuits 20a and 20b of the stop detection circuit 19.
Are output from the first OR circuits 20a and 20b together with an undervoltage signal from another recirculation system (not shown).

The outputs of the first OR circuits 20a and 20b are ANDed by the first AND circuits 21a and 21b together with the selected control rod area signals S25a and S25b output from the nuclear instrument panel 25 at this time. When both signals are input, it is determined that the recirculation pump 1 is stopped and is in the selected control rod control area, and the first AND circuit 2
Signals are output from 1a and 21b to the second OR circuit 22a. Thus, the output of the second OR circuit 22a is input to one input terminal of the second AND circuit 23.

In a nuclear power plant, since the output control of the reactor in response to an erroneous signal due to a failure of a single unit of the equipment affects the safety and the operation rate of the reactor, the instruments having the same detection phase are used. Two undervoltage relays 17a and 17b are connected to the transformer 15 for multiplexing, and a logic circuit is formed in the stop detection circuit 19. Is operated, and the re-circulation pump 1 is determined to be stopped based on the presence or absence of power applied to the drive motor 2 by mutually confirming voltage signals in different phases with the same power supply.
In addition, the safety and reliability are enhanced by judging operation based on control conditions such as a selected control rod area signal output from the nuclear instrument panel 25 or the like.

That is, even if one of the two undervoltage relays 17a and 17b connected to the same instrument transformer 15 is defective and one of the undervoltage signals S17a and S17b is not output, Either one of the undervoltage signals may be used, and the other condition, the selection control rod area signal S2
5a and S25b are output, the second OR circuit 2
2a emits an output.

When three-phase power is lost, not only the voltage between one two-phase (line-to-line) is lost, but also the voltage between the other two phases is always lost. Therefore, when the circuit breaker 9 is opened and the power to the drive motor 2 is lost and the recirculation pump 1 stops, the two undervoltage relays connected to the instrument transformer 15 in the stop detection device 14 17a, 17b as well as another instrument transformer 1
6, the undervoltage relays 18a and 18b also detect the loss of voltage and respectively detect the undervoltage signal S17.
a, S17b and undervoltage signals S18a, S18b.

As a result, the second OR circuits 22a and 22b
Is input to an input terminal of a second AND circuit 23. The second AND circuit 23 outputs the
The power supply to the recirculation pump 1 is provided on condition that the output signals from the second OR circuit 22a and the second OR circuit 22b due to the voltage loss between the two different two phases detected at 5 and 16 are input. Loss, that is, the stop signal S of the recirculation pump 1
23 (in this case, a selection control rod insertion signal) is output.

If only a signal of a voltage drop or loss between two phases (for example, the output of the second OR circuit 21a) is input due to an abnormality in the power supply device 8, a second AND operation is performed. Since the logical condition in the circuit 23 is not satisfied, the stop signal S23 of the recirculation pump 1 is not output.

The first OR in the stop detection circuit 19
An output from an undervoltage relay of another recirculation system (not shown) of the same reactor is input to the other input terminals of the circuits 20a, 20b, 20c, and 20d. Stop detection of the system recirculation pump can be performed. That is, the stop detection device 14 can monitor the stop of the recirculation pump for one nuclear reactor.

FIG. 2 is a block diagram showing another embodiment of the present invention. The difference from the embodiment of FIG. 1 is that a power supply device 8 comprising a motor 5, a speed change mechanism 6 and a variable speed generator 7 is provided. Static type variable voltage variable frequency power supply device 26 and output transformer 27
The configuration, operation, and effect of the other stop detection devices 14 are the same.

In the above embodiment, the case where a three-phase power supply is used and the voltage applied to the drive motor 2 of the recirculation pump 1 is detected by the instrument transformers 15 and 16 has been described. Alternatively, a current transformer may be used to detect the loss of the current flowing through the drive motor 2, and the condition to be combined with the stop information of the recirculation pump 1 may be used to select the reactor power control. Although the case of adopting the control rod insertion has been described, the stop of the recirculation pump 1 can be similarly confirmed even if this combination condition is set to another. In the case of two recirculation systems, only one of them is shown. However, for a type in which a large number of recirculation pumps are housed in a nuclear reactor (internal pump), the detection device in the stop detection device and By installing the logic circuits in accordance with the number of recirculation pumps and the like, the same effects as in the above embodiment can be obtained.

[0023]

As described above, according to the present invention, it is possible to accurately detect the stop of the recirculation pump of the reactor coolant which is installed in the reactor containment vessel and is difficult to monitor. It is also easy to combine signals from other reactor controls and the like, and there is an effect that the operation rate, safety and reliability of the reactor operation are improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a recirculation pump stop detection device of the present invention.

FIG. 2 is a configuration diagram of a stop detection device showing another embodiment of the present invention.

FIG. 3 is a drive system diagram of a recirculation pump.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Recirculation pump, 2 ... Drive motor, 11 ... Electric circuit, 14
... Stop detection device, 15, 16 ... Instrument transformer, 17a,
17b, 18a, 18b: undervoltage relay, 19: stop detection circuit, 20a, 20b, 20c, 20d: first O
R circuits, 21a, 21b, 21c, 21d: first AN
D circuit, 22a, 22b ... second OR circuit, 23 ... second
AND circuit of 25, nuclear instrumentation board.

Claims (1)

(57) [Claims] A plurality of detecting means installed in an electric circuit of a drive motor for driving a recirculation pump of a reactor coolant and detecting that voltages or currents having different phases applied to the drive motor have respectively dropped below predetermined values; And a stop detection circuit for outputting a stop signal for the recirculation pump when signals output from the plurality of detection means are input together.