JPH0355120Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a bypass circuit that bypasses the logic of a nuclear reactor protection system.

[Technical background of the invention]

A nuclear power plant is equipped with a reactor protection system that detects when an abnormality occurs in the reactor and causes an emergency shutdown of the reactor. This reactor protection system consists of various sensors and logic circuits that detect abnormalities in the reactor. When an abnormality is detected by a sensor, a scram signal is generated and control rods are urgently inserted using hydraulic pressure. automatically shuts down the reactor. Therefore, the reactor protection system is very important and must be in operation at all times during reactor operation.

[Problems with background technology]

However, if the reactor protection system is always in operation in this way, there is a possibility that a scram signal will be generated erroneously when the sensor is calibrated, maintained, etc. while the reactor is shut down. When this scram signal occurs, high pressure is applied to the control rods that have already been fully inserted to perform emergency insertion, which prevents deformation of the control rod drive device and shortening of its life due to excessive stress. I will invite you.

To prevent this situation, it is possible to install a bypass circuit in the logic circuit of the reactor protection system to prevent scram signals from occurring during sensor calibration and maintenance. Failure to reset a bypass switch that was turned on during reactor operation or when the reactor was stopped may cause an accident in which the reactor operation is restarted without the reactor protection system operating.

[Purpose of the invention] The present invention was developed in view of the problems of the conventional technology, and is intended to prevent the erroneous generation of scram signals during sensor calibration and maintenance, and to prevent the occurrence of erroneous scram signals when the reactor protection system is not operating. The purpose is to provide a bypass circuit for the reactor protection system that can prevent the reactor from being operated.

[Summary of the idea]

To achieve the above objectives, the present invention includes a bypass switch that enables bypass and activates an alarm when turned on, and an interlock contact that closes only when the reactor satisfies predetermined safety conditions. and a time-limited contact, which is energized while issuing an alarm when the bypass switch is turned on, are connected in series, effectively preventing the bypass during reactor operation or forgetting to return the bypass switch, and allowing the bypass switch to be activated as needed. It is possible to bypass the logic of the reactor protection system.

[Example of idea]

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

The figure is a system diagram showing a nuclear reactor protection system including an embodiment of the bypass circuit according to the present invention. Closed contact groups 9 and 1
0 and the excitation coil 11 of the scram relay are connected in series to form a reactor protection system.
This normally closed contact group 9 is a collection of switches that open when an important abnormality item that should not be bypassed even when the reactor is shut down is detected, and the normally closed contact group 10 is a set of switches that are opened when a critical abnormality item that should not be bypassed even when the reactor is shut down is operated. This is a collection of switches that correspond to abnormal items.

The bypass circuit according to the present invention has a normally closed contact group 10.
A bypass switch 1, an interlock contact 3, and a timer contact 5 are connected in series. Also,
A timer excitation coil 4 that closes the timer contact 5 for a predetermined time by energizing it, and an auxiliary switch 2 that operates in conjunction with the bypass switch 1 are connected in series between the power supply bus 12 and the ground wire 13. Alarm relay 6 is timer excitation coil 4
are connected in parallel. These timer excitation coils 4 and alarm relays 6 are energized to activate alarm devices 7 and 8, such as buzzers and lamps, respectively.
to drive. In addition, the above-mentioned interlock contact 3 is an interlock permission signal that is generated from a control device (not shown) when it is determined that the device itself satisfies certain limiting conditions in order to prevent malfunctions of the reactor and erroneous operations by operators. Closed by INT. The conditions for generating this interlock permission signal can be arbitrarily combined depending on the reactor and system, but for example, the mode switch is in the fuel rod exchange position,
The reactor pressure should be 1 Kg/cm ² or less, the reactor water temperature should be 100° C. or less, etc. in an appropriate combination.

Next, the operation of this bypass circuit will be explained.

If no abnormality has occurred in the reactor shutdown state, all the contacts in the normally closed contact groups 9 and 10 are in the closed state, and the scram relay excitation coil 11
is constantly energized between the power supply bus 12 and the ground wire 13, preventing reactor scram from occurring.

If you turn on bypass switch 1 in this state,
In conjunction with this, the auxiliary switch 2 is turned on, and the timer excitation coil 4 and alarm relay 6 are energized. The timer contact 5 is closed by the energization of the timer excitation coil 4, and is opened again after a predetermined time has elapsed. Similarly, the alarm device 7 is driven by this timer and generates an alarm while the timer contact 5 is closed. Furthermore, the alarm device 8 is driven by the alarm relay 6 while the bypass switch is in the closed state.

On the other hand, when the reactor is in a stopped state and predetermined safety conditions are met, the interlock contact 3 is closed by an interlock permission signal from a control device (not shown). Therefore, on the contrary, bypass cannot be performed while the reactor is operating.

By closing all of the bypass switch 1, interlock contact 3, and timer contact 5 in this way, it becomes possible to bypass the reactor protection system, and while the normally closed contacts 10 are opened, maintenance and calibration of the sensor can be carried out, for example. It can be performed.

Alarms 7 and 8 warn that the logic of the reactor protection system is being bypassed. Further, due to the operation of the timer, the timer contact 5 is opened after a predetermined period of time has elapsed, and the bypass circuit is automatically released. At this time, since the alarm device 8 is driven by the alarm relay 6 while the bypass switch 1 remains on, the operator is notified that the bypass switch 1 has been turned off.

Note that when one of the contacts in the normally closed contact group 9 becomes open, it means that a serious abnormality has occurred, so the excitation coil 11 of the scram relay becomes de-energized regardless of whether there is a bypass or not. A furnace scram is performed.

In the above embodiment, the bypass switch 1,
The interlock contact 3 and timer contact 5 are connected in series in this order, but the order does not matter as long as these components are connected in series.
Further, other contacts or the like may be present. Furthermore, although an open delay type time-limited contact is used as the timer contact in the embodiment, a closed delay type, that is, a normally closed contact that opens after a predetermined period of time has elapsed may also be used. Note that the operating time of the time-limited contact can be arbitrarily selected in consideration of the time required for maintenance, calibration, etc. Further, the alarms 7 and 8 can be of any known type other than the above-mentioned buzzer and lamp, and can also display, for example, the remaining time of the timer setting time.

[Effect of idea]

As described above, the bypass circuit of the reactor protection system according to the present invention includes an interlock contact that is closed only when a predetermined safety condition is satisfied, and a bypass switch that activates an alarm when turned on.
Since it has a configuration in which a time-limited contact is connected in series with a time-limited contact that is energized while issuing an alarm when the bypass switch is turned on, bypass is not performed when the bypass conditions are not met, preventing erroneous bypass during reactor operation. In addition, since bypassing is performed within the time required for sensor maintenance, calibration, etc., the reactor is not started up or operated with the reactor protection system bypassed, which increases the safety of the reactor. Enables bypass in a maintained state. Further, since a warning is issued regarding the closing of the bypass switch and the closing of the time-limited contact, the operator can be appropriately informed of the state of the bypass circuit, further increasing safety.

[Brief explanation of drawings]

The figure is a system diagram showing a partial configuration of a nuclear reactor protection system having a bypass circuit according to the present invention. 1... Bypass switch, 2... Auxiliary switch, 3... Interlock contact, 4... Timer excitation coil, 5... Timer contact, 6... Alarm relay,
7, 8... Alarm, 9, 10... Normally closed contact group, 1
1... Scram relay excitation coil, 12... Power bus, 13... Earth wire.

Claims (1)

[Scope of Claim for Utility Model Registration] In a bypass circuit of a reactor protection system that bypasses a part of the logic of the reactor protection system that makes an emergency shutdown of the reactor in the event of an abnormality as necessary, the bypass circuit enables bypass by turning on the system. a bypass switch that activates the alarm; an interlock contact that closes only when the reactor is in a stopped state and satisfies predetermined safety conditions; A bypass circuit for a nuclear reactor protection system, characterized in that a time-limited contact that is energized and is directly connected.