JPS59155790A - Thermal power monitoring 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 [Field of Application of the Invention] The present invention relates to a thermal power monitoring device for a boiling water nuclear reactor, and in particular to a recirculation system used to determine a set point for a reactor emergency shutdown (scram). The present invention relates to a thermal output monitoring device with improved circuitry for processing water flow signals.

[Prior art]

In a boiling water reactor, thermal output is controlled not only by control rods but also by the flow rate of recirculating water, and is configured to perform an emergency shutdown when the thermal output exceeds a certain limit. A thermal output monitoring device is used to do this, but this device has problems with its maintainability, and an explanation of the problem and how to improve it is published in Japanese Patent Application No. 1986-8.
7509. FIG. 1 is a diagram showing the overall configuration of the thermal output monitoring device, and FIG. 2 shows an example of the above-mentioned improvement method. % In Application No. 56-87509, the average output monitor circuit has a 4-channel configuration of 51A-D for explanation purposes, but in actual plants, it is usually configured with 51A-F.
It has a 6-channel configuration.

Since the outline of the thermal output monitoring device and the detailed explanation of FIGS. 1 and 2 are described in Japanese Patent Application No. 56-87509, FIG. 2 will be briefly explained here.

The circuit shown in FIG. 2 is used, for example, for maintenance or testing of the flow rate signal processing circuit 6A, by operating the bypass switch 13A to disconnect the output of the internal output buffer 62 from the average output monitor circuit, and to cut off the output of the internal output buffer 62 from the average output monitor circuit.
, 91C, and 91B are controlled so that they become the signal f6 from the flow rate signal processing circuit 6C. As a result, the overall signal flow of the thermal output monitoring device becomes as shown in FIG. 3, and since the flow rate signal f is not used within the device (indicated by a broken line), maintenance of the flow rate signal processing circuit 6A is easy. And it can be done safely.

By the way, in this case, as is clear from FIG. 3, the scram setting values of the average output monitor circuits 6A, 6C, and 6B are all determined by the flow rate signal fc.
Alternatively, assuming that a failure occurs inside the signal processing circuit 6C and the flow rate signal fC becomes abnormally larger than the normal value, the average output monitor circuits 51A, 51C, and 51E will issue a normal scram signal when the reactor is abnormal. This means that the heat output monitoring device loses its scram function. In reality, the flow rate signal processing circuit is provided with a monitor circuit, and any abnormality in the flow rate signal is immediately detected, so that it is possible to take immediate action.

However, for the safety of a nuclear reactor, even during maintenance, the scram function of the reactor must not be lost even temporarily due to a single failure.

[Purpose of the invention]

The present invention was conceived in view of these problems.
An object of the present invention is to provide a thermal output monitoring device that prevents the scram function from being lost even if there is an abnormality in other operating flow signal processing circuits, in order to safely and easily inspect flow signal processing circuits. .

[Summary of the invention]

In the present invention, when inspecting a flow rate signal processing circuit, by operating a switch from the outside, instead of this circuit output, other flow rates that are input to different low value selection circuits (i.e., average output monitors) are detected. It is characterized by being equipped with a circuit that switches to a signal.

[Embodiments of the invention]

The present invention will be explained below with reference to FIG. First, bypass switches 13A to 13D are provided, and any one of bypass relays 61A to 61D is operated by these switches. If the flow rate signal processing circuit 6A is bypassed, its output is the low value selection circuit 91A.

Switch to a signal that is not input to 91C and 91E. Here, it is assumed that the output is temporarily switched to the output of the flow rate signal processing circuit 6B. As a result, the low value selection circuits 91A, 9
Since the flow signals of the flow signal processing circuits 6C and 6B are input to 1C and 91E, even if a failure occurs in either 6C or 6B and that signal becomes abnormally high, the other normal signal will be input. It is selected as a low value so that the scram function of the reactor is not disturbed. If the other flow rate signal processing circuits are configured with switching circuits as shown in FIG. 4, the same functions as described above can be achieved. .

It goes without saying that the present invention is not limited to the embodiment shown in FIG. 4, and that a complementary circuit configuration having a similar function of switching the flow rate signal to a signal from another circuit is possible.

〔Effect of the invention〕

As described above, according to the present invention, the output of the flow rate signal processing circuit to be inspected is switched to the signal that is input to the different average output monitor circuits. This has the effect of maintaining the scram function of the reactor even if a single failure occurs within the flow signal processing system.

[Brief explanation of the drawing]

1, 2, and 3 are circuit diagrams showing conventional embodiments, and FIG. 4 is a circuit diagram showing an embodiment of the present invention.

Claims (1)

[Claims] 1. It has a flow rate signal processing circuit for converting the signals obtained by measuring the flow rate of recirculating water in a boiling water reactor with a plurality of flow rate measuring devices into flow rate signals, and selects a low value for each of the flow rate signals. A thermal output monitoring device comprising a plurality of average output monitoring circuits that determine a reactor scram value according to the obtained signal and output an emergency shutdown signal for the reactor when the reactor thermal output exceeds the scram value. A thermal output monitoring device characterized in that the output of the flow rate signal processing circuit is switched by an external operation to the output of another flow rate signal processing circuit serving as an input of a mutually different average output monitor circuit.