JPH03262995A - Monitor device for nuclear reactor scramming circuit - Google Patents

Abstract

PURPOSE:To prevent a control rod from being inserted fast carelessly by connecting the monitor device which monitors the circuit current of a scramming pilot valve solenoid circuit to the circuit and informing an operator that the circuit current decreases below a reference current in such a case. CONSTITUTION:The monitor device 11 is connected to the scramming pilot valve solenoid 6A in series and the output of the device is led to a warning device 12. Resistances RA and RB shunt only a current which is weak enough not to affect the solenoid 6A to the rectification device consisting of a diode bridge D1 and the current is rectilied on a full-wave basis into a DC current I2. The current I2 is rectified by the smoothing filter which uses a capacitor C, a diode D2, and a resistance RC into DC current I3. The current I3 flows through a photodiode D3 which switches when a current exceeding the reference current flows and returns to the rectification device. When the current I3 decreases below the reference current, the diode D3 switches to send a warning to the warning device 12 through an output circuit 13, thereby informing the operator of that.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a reactor scram circuit monitoring device for monitoring a reactor scram circuit installed in a reactor safety protection system of a nuclear power plant. .

(Conventional technology) In nuclear power plants, as a function of the reactor safety protection system, control rods are rapidly inserted into the reactor (hereinafter referred to as nuclear It is necessary to stop nuclear fission in the reactor core as soon as possible to prevent fuel damage, and for this reason a reactor scram circuit is installed.

The configuration of this reactor scram circuit will be explained with reference to FIG.

In the reactor scram circuit shown in FIG. 3, the reactor emergency shutdown system operating circuit bus IA connected to different power supply systems,
The IB has two reactor scram logic circuits (hereinafter referred to as trip channels) corresponding to each of these busbar circuits. That is, trip channel 2AI and trip channel 2A2 correspond to bus line IA.
It is equipped with a trip channel 2B and a trip channel 2B2 corresponding to bus line IB. Further, each trip channel has a scram contactor 3A, 3C or 3B, 3D.

During normal operation of the reactor, scram contactors 3A, 3
C, 3B, 3D are always excited, and the auxiliary contacts 3AI, 3C+, 3B+,
3D+ is a closed circuit.

In the reactor emergency shutdown system operating circuit bus line IA thread system, a single rod scram test switch 4A is installed between the scram contactor 3C and the auxiliary contact 3C of the scram contactor, each of which can perform a scram test for each control rod.
A scram pilot valve solenoid 6A that scrams the control rods is connected to each control rod via a circuit protection fuse 5A. Similarly, in the reactor emergency shutdown system operating circuit bus line IB thread system, a single rod scram test is performed between the scram contactor 3D and the auxiliary contact 3D1 of the scram contactor, which allows a scram test to be performed for each control rod. A scram pilot valve solenoid 6B that scrams each control rod is connected to each control rod via a switch 4B and a circuit protection fuse 5B.

Scram pilot valve solenoids 6A and 6B are control rod 1
Each rod is attached to a scram pilot valve in pairs, and when solenoids 6A and 6B become de-energized at the same time, the scram pilot valve opens and the control rod is rapidly inserted.

The number of control rods in a BWR type nuclear power plant is 137 for the 780,000 kW type, and 18 for the 1.1 million kW type.
There are 5, and the scrum test switch is 4A.

4B, circuit protection fuses 5A, 5B, and scram pilot valve solenoids 6A, 6B are each twice the number of control rods, that is, 274 for the 780,000 kW type.
In the 1.1 million kW type, 310 units are installed each.

In the reactor scram circuit configured as described above, during normal operation of the reactor, the contacts of the single rod scram test switches 4A and 4B are selected to the normal side,
The scram pilot valve solenoids 6A and 6B are constantly excited by AC power from the reactor emergency shutdown system operating circuit buses IA and IB.

When tripping, scram contactor 3A.

3C, 3B, and 3D are non-energized, and their auxiliary contacts 3
A1.3C1 and 3B1.3D1 are opened.

Further, during the reactor scram test, the contacts of the single front scram test switches 4A and 4B are switched to the scram side.

As a result of the above, the scram pilot valve solenoids 6A and 6
Both B are energized during normal times, only one is de-energized during a half scrum test, and both are de-energized during a scrum.

(Problems to be Solved by the Invention) In the conventional reactor scram circuit described above, during operation of the reactor, the scram pilot valve solenoids 6A and 6B of either one of the reactor emergency shutdown systems A and B are not energized. There was a technical problem in that even if something existed, it could not be detected.

Possible causes of this state include a break in the scram fuse, a break in the circuit wiring, and a break in the scram pilot valve solenoid.

If this condition occurs in the scram circuit of a single control rod, a half scram test (-simultaneous demagnetization) in which all the scram pilot valve solenoids of one system are de-energized all at once, which is carried out periodically at nuclear power plants, is performed. When you carry out the test),
Since the scram pilot valve solenoids 6A and 6B of both A%B channels of this one control rod become non-energized, the control rod enters a scram state, and the control rod is rapidly inserted into the reactor.

In this case, there will be fluctuations in the reactor output, and there is concern that it will have an adverse effect on the fuel and control rods.

Although fuses with a disconnection indicator may be used as the circuit protection fuses 5A and 5B, circuit disconnections other than fuse disconnections, scram solenoid disconnections, etc. cannot be monitored. Moreover, many other switches are connected to the solenoid circuit of each scram pilot valve, and there are many wiring connections, so if a fuse has a disconnection indicator, one scram pilot valve solenoid 6A, 6B will be disconnected. Even if something is excited, it cannot be completely detected.

The present invention has been made to solve the above-mentioned technical problems in the prior art.

[Structure of the Invention] (Means for Solving the Problems) The reactor scram circuit monitoring device of the present invention is a nuclear reactor scram circuit that has a function of rapidly inserting control rods into a nuclear reactor. A monitoring device for monitoring the circuit current is connected to the circuit, and when the circuit current is in a non-energized state or drops below a predetermined standard current, the operator is notified of this.

(Function) In the reactor scram circuit monitoring device of the present invention configured as described above, the energizing current of the scram circuit of each control rod is monitored, and if it is equal to or higher than the standard current, it is determined to be normal and it is determined to be abnormal. If the current is on or below the standard current, it is determined that the wire is disconnected.

(Example) Next, the present invention will be described in detail with reference to the drawings. In FIGS. 1 and 2, the same parts as in FIG. 3 are given the same reference numerals, and explanations of the same parts will be omitted unless necessary.

FIG. 1 shows the main parts of a nuclear reactor scram circuit monitoring device according to the present invention. A monitoring device 11 is connected in series to the scram pilot valve solenoid 6A, and the output of this monitoring device is guided to an alarm device 12.

FIG. 2 shows an example of the circuit configuration of the monitoring device 11, in which a portion of the circuit current 11 flowing to the scram pilot valve solenoid 6A is controlled by a resistor RA and a resistor RB to a weak current that does not affect the solenoid 6A. , the current is shunted to a rectifier consisting of a diode bridge D1, where it is full-wave rectified and converted into a direct current I2.

Furthermore, the DC current 12 is passed through the capacitor C1 and the diode D.
2. It is rectified by a smoothing filter using a resistor Re and converted into a direct current 13.

This DC current I3 flows through a photodiode D3 which switches when the current exceeds a reference current and returns to the rectifier.

As a result, when the DC current 13 is higher than the reference current, the photodiode D3 does not switch and does not produce an output. On the other hand, when the DC current I3 becomes equal to or less than the reference current, the photodiode D3 switches and outputs an alarm to the alarm device 12 via the output circuit 13 to notify the operator.

As described above, a signal electrically isolated from the scram solenoid 6A can be extracted by the photodiode D3.

With the above, it is possible to detect when no current is flowing through the scram pilot valve solenoid 6A due to a disconnection or the like.

In addition, in the above explanation, only the monitoring device 11 attached to one scram pilot valve solenoid 6A was explained, but a similar monitoring device can be used for other scram pilot valve solenoid 6A and scram pilot valve solenoid 6B of other series. is included.

As described above, according to the present invention, a disconnection in the reactor scram circuit is automatically displayed, so that the operator can stop the transition to the half scram test, and unnecessary reactor scrams can be prevented.

It goes without saying that the functions of the monitoring device in the above embodiments can also be realized by an electronic computer.

Further, the reactor scram circuit monitoring device of the present invention can also be realized by using fuses with energization display function as the circuit protection fuses 5A and 5B in place of the monitoring device 11 of FIGS. 1 and 2.

As this fuse with an energization display function, for example, a energized light-emitting type fuse that emits light itself when energized can be used.

When using this fuse with a energized display function, unlike the case of conventional fuses with a disconnection display function, it is necessary to
In addition to disconnections in A and 5B, disconnections in scram pilot valve solenoids 6A and 6B, and poor contact in the single rod scram test switches 4A and 4B and the connections of each wiring.
Even in a non-energized state due to a disconnection in each part of the wiring, the non-energized state is displayed, so the non-energized state can be reliably monitored regardless of the cause.

[Effects of the Invention] As explained above, according to the nuclear reactor emergency shutdown device according to the present invention, inadvertent rapid insertion of control rods can be prevented, and reliability and stability of operation can be improved. .

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing an embodiment of the reactor scram circuit monitoring device of the present invention, Fig. 2 is a circuit diagram showing an embodiment of the monitoring device in the device of the present invention, and Fig. 3 is a conventional reactor scram circuit. It is an explanatory diagram illustrating. IA, IB...Reactor emergency shutdown system operating circuit busbar 3A~
3D...Scram contactor 4A-4D...Single rod scram test switch 5A, 5B...Circuit protection fuse 6A, 6B...Scram pilot valve solenoid 11
...Monitoring device 12...Alarm device

Claims (1)

[Claims] In a reactor scram circuit that has the function of rapidly inserting control rods into a nuclear reactor, a monitoring device that monitors the circuit current is connected to the scram pilot valve solenoid circuit, and the circuit current is in a de-energized state or a predetermined reference current. 1. A nuclear reactor scram circuit monitoring device, characterized in that it is configured to notify an operator when the level has decreased further.