JPS59107298A - Recirculation flow rate control device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a recirculation flow rate control device for a boiling water nuclear reactor, and in particular to a system for stopping a nuclear reactor when abnormal reactor power increases due to equipment failure. Recirculation flow control devices that can be avoided.

[Technical background of the invention and its problems]

In conventional boiling water reactors, when there is an abnormal increase in reactor output due to a failure of the recirculation flow control device, the neutron flux in the power range is detected and the reactor protection system is activated to bring the reactor to an emergency shutdown. . By the way, the recirculation flow rate control device is
There are two reactors installed at the base, so even if one fails, the other will remain in a healthy state, and even if the failure loop is stopped and the reactor continues to operate, the stability of the reactor will be maintained. Operation is possible as long as the output is at a level that does not impair the performance. Furthermore, if the nature of the failure can be dealt with relatively quickly, it will not take a long time to restore the failed loop, and the reactor may not necessarily have to be shut down immediately.

Therefore, there has been a need for a device that can maintain the operation of the nuclear reactor by reducing the total reactor output when one of the recirculation flow rate control devices fails.

[Purpose of the invention]

An object of the present invention is to provide a recirculation flow rate control device that can avoid a nuclear reactor shutdown by alleviating an abnormal increase in output by stopping the operation of a recirculation pump, and can continue the operation of a nuclear reactor. Our goal is to provide the following.

[Summary of the invention]

A recirculation flow rate control device according to the present invention includes a main controller that outputs a flow rate control signal for a recirculation system in a boiling water nuclear reactor;
The output signal from this main controller is input to a manual/automatic controller that switches the control mode, and the output signal from this manual/automatic controller and the recirculation flow rate measurement signal are input to calculate the deviation of both signals. A deviation calculator, a regulator that adjusts the recirculation flow rate so that the deviation signal becomes 0 based on the deviation signal from this calculator, and a failure detector that detects failures in each of these devices and outputs failure detection signals. and an AND circuit which receives the failure detection signal and the abnormal increase in furnace output = fa and outputs a recirculation pump stop signal based on the AND of both signals.

[Embodiments of the invention]

A first embodiment of the present invention will be described with reference to FIGS. 1 to 5.

Reference numeral 2 in FIG. 1 is a main controller, and this main controller 2 outputs a flow rate control signal for the recirculation system. This signal is input to the deviation calculator 6 via the manual/automatic controller 4. The manual/automatic controller 4 switches the flow rate control mode between manual and automatic. In the manual mode, it outputs a signal according to the set value set by the manual/automatic controller 4, and in the automatic mode, it outputs a signal according to the setting value set by the manual/automatic controller 2. The device is configured to transmit a signal. The flow rate measurement signal 8 from the recirculation system is inputted to the deviation calculator 6, which compares it with the signal from the manual/automatic controller 4 to calculate the deviation between the two signals. is configured to output to. regulator, 1
2 is a flow rate adjustment signal 1 so that the deviation signal 10 becomes O.
4 to adjust the flow rate of the recirculation system.

Output signal from the manual/automatic controller 4, deviation signal 10
, the flow adjustment signal 14 and the flow measurement signal 8 are input to a fault detector 16 . The failure detector 16 is configured to monitor the absolute value and rate of change of each input signal, and output a failure detection signal 18 when it is determined that each signal has entered an abnormal state. This failure detection signal 18 is input to an AND circuit 20. The reactor power supply/i rise signal 22 is input to the AND circuit 20, and a recirculation four-end stop signal 24 is sent out by the AND of both signals.

The operation of such a device will be explained. If the furnace output abnormally increases due to a failure in each device of the main controller 2 or regulator 12, a failure detection signal 1 is sent to the AND circuit 20.
8 and the abnormal furnace output increase signal 22 are input, and the recirculation port/76
A stop signal 24 is output. Recirculation pump stop signal 24
When the recirculation port is stopped, the recirculation flow rate decreases and the det rate in the core increases. When the DETO rate increases, the number of thermal neutrons in the core decreases, the reactivity of the core decreases, and the output decreases.

At this time, as shown in Figures 2 and 3, the range of heat flux change and the minimum power ratio of the core with respect to the elapsed time T from the occurrence of the abnormality do not change significantly, and the health of the fuel rods that make up the core remains unchanged. In addition, when the recirculation pump is stopped, the margin for the stop signal output of the thermal monitor, which is the second stage reactor stop signal system, is at least 10% as shown in Figure 4. It is secured. Furthermore, as shown in Figure 5, the output P8 of the thermal power monitor is always at a lower level than the stop signal output level P8, so even if the recirculation pump is stopped, the reactor will be shut down according to the thermal power monitor. You can continue driving without any problems.

In the above device, the failure detector 16 detects a failure in each device, and when the furnace output abnormally increases due to this failure, a recirculation pump f,=R-stop signal 24 is sent to the recirculation pump. can be stopped. Therefore, the operation can be continued without an emergency shutdown of the reactor in a state where the reactor output is reduced.

〔Effect of the invention〕

As explained above, according to the present invention, when there is an abnormal increase in the reactor output due to a single failure of the equipment of the recirculation flow rate control device, a shutdown of the reactor is avoided and the health of the fuel is improved and the reactor is stabilized. It is possible to provide a recirculation flow rate control device that allows continued operation at low output without impairing performance. Furthermore, since it becomes possible to repair malfunctioning parts during operation, the operating rate of the reactor can be expected to improve, and the effects are outstanding.

[Brief explanation of drawings]

Figures 1 to 5 are diagrams explaining one embodiment of the present invention. Figure 1 is a diagram of the overall configuration of the device, and Figure 2 shows the relationship between the elapsed time T from the occurrence of an abnormality and the width of heat flux change. Characteristic diagram shown, 3rd
The figure is a characteristic diagram showing the relationship between the elapsed time T and the minimum output ratio, FIG. It is a characteristic diagram similarly showing the relationship between elapsed time and thermal power monitor output. 2... Main controller, 4... Manual/automatic controller, 6...
- Deviation calculator, 8... Flow rate measurement signal, 10... Deviation signal, 12... Adjuster, 14... Flow rate adjustment signal, 1
6... Failure detector, 18... Recirculation pump stop signal, 20... AND circuit, 22... Furnace output abnormal increase signal, 24... Recirculation pump stop signal. Applicant's representative Patent attorney Takeshi Suzu

Claims (2)

[Claims] (1) A main controller that outputs a flow rate control signal for the recirculation system in a boiling water reactor, a manual/automatic operator that receives the output signal from this main controller and switches the control mode, and this manual / A deviation calculator that receives the output signal from the automatic controller and the recirculation flow rate measurement signal and calculates the deviation between the two signals, and calculates the recirculation flow rate so that the deviation signal becomes O based on the deviation signal from this calculator. A regulator that adjusts the temperature, a failure detector that detects failures in each of these devices and outputs a failure detection signal, and a recirculation pump stop signal that is inputted with this failure detection signal and the abnormal furnace output increase signal by the logical product of both signals. A recirculation flow rate control device comprising: an AND circuit that outputs . (2) The failure detector receives the output signal from the manual/automatic controller, the deviation signal from the deviation calculator, the flow rate adjustment signal from the regulator, and the recirculation flow rate setting signal, and controls each device based on these signals. 2. The recirculation flow rate control device according to claim 1, wherein the recirculation flow rate control device detects a failure of the recirculation flow rate control device.