JPH0644061B2 - Abnormal flow detector for reactor cooling system - Google Patents

Description

The present invention relates to a method for detecting abnormal flow rate in a reactor cooling system,
Particularly, the present invention relates to an abnormal flow rate detection device suitable for early detection of an abnormal flow rate in a fast breeder reactor cooling system using liquid metal sodium.

A typical example of a fast cooling reactor primary cooling system using liquid metal sodium is shown in FIG. Circulating pump 3 supplies coolant to reactor 1
And the heat exchanger 2 are circulated so that the heat generated in the reactor 1 is removed by the heat exchanger 2. It is customary to install a flow rate detector 4 for measuring the flow rate of the circulation system in the circulation path and a pump tachometer on the extension shaft of the pump. Conventionally, the abnormal flow rate detection of the reactor cooling system is performed by the flow rate signal in which the signal of the flow meter is regulated in plant operation, for example, when the flow rate is operated at a constant flow rate, the constant flow rate value is proportional to the reactor output. When changing the operation, the flow rate value determined according to the reactor output is used as a reference flow rate, and the reference flow rate is compared with the actual flow rate. The method of making it abnormal is taken. Since such a flow rate abnormality detection method is simple, it is an effective abnormality detection means.However, if the measurement accuracy of the flow meter is not very good or there is a fluctuation component in the flow meter signal, the There is a drawback that the allowable deviation must be increased and the abnormality detection sensitivity is reduced.

An object of the present invention is to provide a means for detecting a flow path abnormality in a reactor cooling system at an early stage by comparing the rate of change between the pump rotational speed that gives a change in flow rate and the actual flow rate.

The present invention is intended to provide a more reliable and early abnormality detecting means by complementing the above-mentioned abnormal flow detecting means according to the prior art. As described above, when the measurement accuracy of the flowmeter is not very good, or when the flowmeter signal has a fluctuation component, the allowable deviation from the reference flow rate must be increased. In the case of abnormality, the conventional abnormality detection method does not operate. It is designed so that the safety of the nuclear reactor is not normally impaired even if such a slight flow rate abnormality occurs, but it is desirable to equip a means for early detection of such abnormality.

The prior art attempts to detect an abnormality using the flowmeter signal alone, but the present invention compares the rate of change of the pump rotational speed that changes the cooling system flow rate with the actual flow rate to detect an abnormality relatively. Is what you are trying to do.

An embodiment of the present invention will be described below with reference to FIG. The flow sensor 6 is a flow sensor installed at the position of the flow meter 4 shown in FIG. 1, and an electromagnetic flow meter is normally used. The electromagnetic flowmeter generates a voltage signal proportional to the flow rate of liquid sodium, which is the reactor coolant. The tachometer sensor 7 is a rotation sensor installed at the position of the tachometer 5 shown in FIG. 1, and a measuring means such as a rotary generator or an electromagnetic pickup is used. In this figure, a rotary generator is used, and the rotary generator generates a voltage signal proportional to the pump rotation speed. The signal converters 8-1, 8-2 convert the voltage signals of the flow rate sensor and the tachometer sensor into current signals. The coefficient unit 9 is a circuit for multiplying the input signal by a predetermined coefficient in order to compare the rotation speed signal with the flow rate signal. Change rate calculator 1
0-1 and 10-2 are for obtaining the rate of change of the signal converted by the flow sensor and the tachometer sensor.
The comparator 11 compares the flow rate and the rotation rate change signals to determine whether the deviation between the two signals exceeds a predetermined threshold value.

When a cooling system flow path is formed and there is no change in the flow path, the pump rotation speed is proportional to the cooling system flow rate. That is, F = α × N ... F: cooling system flow rate (ratio to rated value) N: pump speed (ratio to rated value) α: conversion constant

Therefore, in the circuit shown in FIG. 2, if the coefficient of the coefficient multiplier 9 is selected to a value corresponding to α in the above equation, the signals 21 and 22 are theoretically equal to each other unless the flow path changes.
However, in reality, the difference appears due to the measurement accuracy and fluctuation included in the measurement signal. In order to remove the measurement error and fluctuation, it is a feature of the present invention that the rate of change of the signal is obtained and the two are compared.

Factors that change the cooling system flow rate include fluctuations in the pump drive source and fluctuations in the flow path. When the pump drive source fluctuates, both the pump rotation speed and the cooling system flow rate fluctuate, but when the flow path changes, the pump rotation speed does not fluctuate but only the cooling system flow rate fluctuates. Therefore, the change rate of both is constantly monitored, and if the deviation of the change rate of both changes more than the permissible value, it is detected that the flow path is abnormal due to pressure loss change of the cooling system flow path or breakage of the flow path. it can. In the present invention, since the rotational speed and the change rate of the flow rate are compared, the measurement accuracy of the flow rate and the rotational speed is not affected, and the fluctuation component such as fluctuations added to the flow rate signal is calculated by the change rate. It is possible to prevent the fluctuation component from being affected by increasing the coefficient.

According to the present invention, even when the measurement lightness of the flowmeter of the reactor cooling system is not so good or the flowmeter signal has a fluctuation component, it is possible to reliably and early detect the abnormality of the flow path.

[Brief description of drawings]

FIG. 1 shows a fast breeder reactor 1 using liquid metal sodium.
FIG. 2 is a conceptual diagram showing a typical example of the next cooling system, and FIG. 2 is an explanatory diagram of an embodiment of the abnormal flow rate detection device of the reactor cooling system according to the present invention. 1 ... Reactor, 2 ... Heat exchanger, 3 ... Coolant circulation pump, 4
... Flow rate detector, 5 ... Pump tachometer, 6 ... Flow rate sensor, 7
... Tachometer sensor, 8-1, 2 ... Signal converter, 9 ... Coefficient device, 10-1, 2 ... Change rate calculator, 11 ... Comparator.

Claims (1)

[Claims] 1. A reactor cooling system comprising a reactor coolant circulation pump, piping, a heat exchanger, etc., wherein a flow meter is installed in the cooling system flow passage piping and a tachometer is installed in the circulation pump. And a rate of change of the tachometer signal are compared with each other, and an abnormality in the reactor cooling system is detected when the deviation exceeds a specified value, thereby detecting an abnormal flow rate in the reactor cooling system.