JPS5856821B2 - Liquid metal leak detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid metal leak detection device, and more particularly to a liquid metal leak detection device in which output signal transmission means of a plurality of short-circuit leak detectors is improved.

The principle of a conventional wire-type sodium leak detector will be explained with reference to FIG.

The leak detection wire 2 is covered with a fibrous insulation 3 and is wrapped around the sodium pipe 1 or placed along the underside of the pipe 1.

A voltage is applied to this wire by a power source 4 via a resistor 5.

When liquid sodium leaks due to a crack or the like in the pipe 1, the liquid sodium soaks into the fibrous insulator 3, and the leak detection wire 2 and the pipe 1 become electrically connected.

Since the pipe 1 is grounded, the potential of the leakage detection wire 2 decreases.

By measuring this potential with a voltmeter 6, the presence or absence of leakage can be determined.

As described above, the principle of the conventional short-circuit sodium leak detector is simple, but in order to accurately determine the leak location, the detection wire must be shortened and a large number of detectors can be used to detect all leaks. There was a drawback that it had to be installed in possible piping, tanks, etc.

In particular, liquid sodium cooled fast breeder reactors are said to have several thousand detectors.

In such a case, if a signal cable is taken out from each detector, several thousand cables must be routed inside the containment vessel, and these cables must be routed through the walls of the containment vessel.

- The power signal processing system also requires a multiplexer, etc. that sequentially scans all signal lines and measures the voltage.

An object of the present invention is to provide a limb metal leak detection device that can reduce the number of cables.

A feature of the present invention is that the pulse generation means and the leakage determination means are connected by wiring, and each liquid metal leakage detector is connected in parallel to the wiring via a delay circuit, and each delay circuit delays the signal. The time is different, and the leak determination means consists in detecting the leak position of the liquid metal based on the time delay of the output signal of the liquid metal leak detector.

An embodiment in which the present invention is applied to a primary cooling system of a sodium-cooled nuclear reactor will be described with reference to FIG.

The pulse generator 7 is connected to the signal processing system 26 via one cable.
connected to.

A resistor 14 with a matched impedance is attached to the cable.

A leak detection wire 2 shown in FIG. 1 is placed near the pipe 1 through which sodium flows.

Each leakage detection wire 2 has a rectifier 9 and a delay circuit 10
connected in parallel to the cable via.

Since the lengths of the respective delay circuits 10 are different, the delay times of the respective signals are different.

Delay circuit 10 is grounded.

The pulse generator 7 and signal processing system 26 are installed outside the containment vessel.

The rectifier 9 and the delay circuit 10 are installed in the containment vessel together with the pipe 1 through which sodium containing radioactive substances flows, but are protected by a shield to avoid radiation damage.

Pulse generator 7 outputs a single pulse 8.

This pulse signal is sent to each leak detection wire 2 via a resistor 14.

When this pulse signal is input to the leakage detection wire 2,
It passes through a rectifier 9 and a delay circuit 10.

The rectifier 9 is provided to prevent the output signals of other leak detection wires 2 from escaping through the leaked sodium.

In the leakage detection wire 2 located at a position where no leakage occurs,
Since the potential of the wire increases, the current of the input pulse signal almost never flows into the wire.

In the leakage detection wire 2 at the location where the leakage occurs,
The input pulse wave passes through the delay circuit 10 and reaches the sensing wire which is grounded by the leaking sodium.

Since the impedance of the ground point is smaller than the matching impedance of the delay circuit 10, the arriving pulse wave is reflected as a signal with the opposite sign and returns through the delay circuit 10, as shown in FIG.

The time for this reflected pulse wave to reach the signal processing system 26 is
It varies depending on the length of the delay circuit 10.

That is, since it differs depending on each leak detection wire 2, by finding the time difference Δt between the input pulse and the output pulse, the leak detection wire 2 at the position where the leak is occurring, that is, the leak position can be found.

time. The difference Δt is determined by the signal processing system 26.

In this embodiment, since the signal input cable to the leakage detection wire 2 and the signal output cable from the wire 2 are shared, the number of signal input/output cables is only one.

It is also possible to detect leak locations. According to the present invention, although there are a large number of leak detectors, only one signal input/output cable is required, and the structure of the leak detection device is significantly simplified.

At the same time, the location of the leak can be detected.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a conventional liquid metal leak detection device, and FIG. 2 is a circuit diagram of a preferred embodiment of the present invention. 2...Leakage detection wire, 7...Pulse generator, 9.
... Rectifier, 10... Delay circuit, 26... Signal processing system.

Claims (1)

[Claims] 1 A liquid metal leak consisting of a plurality of liquid metal leak detectors placed near a container or pipe in which liquid metal exists, and means for determining the presence or absence of a leak based on the output signal of the limb metal leak detector. In the detection device, a pulse generating means is provided, the pulse generating means and the leakage determining means are connected by wiring, each liquid metal leak detector is connected in parallel to the wiring via a delay circuit, and each A liquid metal leak detection device characterized in that the delay circuits have different signal delay times, and the leak determination means detects the leak position of the liquid metal based on the time delay of the output signal of the liquid metal leak detector. .