JPS59162434A - Leakage detecting device for liquid metal - Google Patents

Abstract

PURPOSE:To make it possible to detect leakage of water or steam into liquid metal in an early stage, by obtaining correlation of a plurality of detected signals with respect to the reacted product of metal and water in the liquid metal flowing in a pipe. CONSTITUTION:Sodium, which is circulated in a secondary main cooling system, flows in a returning pipe 18. The amount of the sodium is detected by a flowmeter 34. The detected signal is supplied to a delay time operator 36. The operator 36 obtains the flow velocity in the pipe 18, computes the time the sodium flows between hydrogen detectors 30 and 32, and feeds the result to correlation function computer 38. The computer 38 receives the detected hydrogen-concentration signals outputted from the detectors 30 and 32, obtains the correlation between the signals, and obtains the signals, from which inherent noises of the detectors are removed.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a device for detecting water leakage into a liquid metal, and particularly for use in a sodium-heated steam generator of an IJium-cooled fast breeder reactor. This invention relates to a water leak detection and detection device suitable for use in water leak detection and detection.

[Prior art]

A sodium-heated steam generator is one in which high-temperature sodium and high-temperature, high-pressure water or steam exchange heat through heat transfer tubes. Therefore, if the heat transfer tube is damaged for any reason, high temperature and high pressure water or steam will be released.)
It erupts into the IJium, causing a violent sodium-water reaction. This sodium/water reaction causes not only the initial failure of the heat transfer tube but also damage between adjacent heat transfer tubes.
Potential for large-scale water leakage. Therefore, it is necessary to quickly discover water leaks in sodium-heated steam generators while they are small-scale, and take appropriate measures to prevent the accident from spreading. Therefore, in the conventional IJum boosted steam generator, a method is used in which hydrogen generated by the disodium-water reaction is detected using a metal diffusion type hydrogen detector to detect water leakage.

FIG. 1 shows the installation position of a metal diffusion membrane type hydrogen detector in the secondary main cooling system in a sodium-cooled fast breeder reactor. In FIG. 1, the intermediate heat exchanger 10 is connected to primary system piping 12, 14, and is also connected to a transfer pipe 16 and a return pipe 18 of the secondary system piping. This transfer pipe 1
6 and a return pipe 18, the secondary main cooling system includes a steam generator.

A superheater 22 and an evaporator 24 of the generator 20 are installed, and a secondary main circulation pump 26 is installed. and,
At the outlet of the superheater 22, the outlet of the evaporator 24, and the inlet of the secondary main circulation pump 26, the aforementioned hydrogen detectors 28 and 30° 32 are provided, respectively, to detect hydrogen produced by the sodium-water reaction. It is.

The primary sodium transferred to the intermediate heat exchanger 10 through the primary system piping 12 exchanges heat with secondary sodium in the intermediate heat exchanger 10, and then is returned to the reactor through the secondary system piping 14. The secondary steam heated in the heat exchanger IO is carried to the superheater 22 via the transfer pipe 16, where it exchanges heat with high-temperature steam, and then with water in the steam generator 24, Generate steam. Thereafter, the secondary sodium is returned to the heat exchanger 10 via the Pb pipe 18 by the secondary main circulation pump 26.

In such a secondary main cooling system, when steam or water leaks into the sodium in the superheater 22 or evaporator 24, hydrogen generated by the reaction between the sodium and the steam or water circulates through the secondary system. Therefore, the hydrogen concentration in sodium detected by each of the hydrogen detectors 28, 30, 32 shows a stepwise change in which the hydrogen concentration C increases at regular intervals, as shown in FIG. Therefore, in order to detect water leakage, the hydrogen concentration increase ΔC during a certain time Δt is
When the rate of increase in hydrogen concentration ΔC/Δt becomes larger than a preset rate of increase in hydrogen concentration, it is determined that water leakage has occurred. In order to improve the reliability of water leakage detection, hydrogen detectors 28 and 30.3 are used to detect water leakage.
A so-called 2-out OP3 multiplexing process is performed in which a judgment is made based on the output signals of two detectors having a large rate of change in the two output signals. However, the hydrogen detector is 28°30.
Since the output signal 32 contains noise frequently generated due to thermal and electrical factors of the hydrogen detectors 28, 30, 32, errors occur in the respective measured values. Therefore, the lower limit value ΔCL, which is the standard for the increase in hydrogen concentration ΔC for detecting water leakage, is set to a value with a certain margin in consideration of the measurement error caused by the noise. Therefore, the measuring time ΔtL for obtaining the lower limit value ΔCL becomes correspondingly longer, which has the disadvantage that detection of water leakage is delayed.

[Purpose of the invention]

The present invention was made in order to eliminate the drawbacks of the prior art, and an object of the present invention is to provide a water leakage detection device for liquid metal that can detect water leakage at an early stage.

[Summary of the invention]

The present invention detects a component generated by a reaction between liquid metal and water or steam in a liquid metal circulating in a pipe by using an upstream concentration detector. Find the time it takes for the liquid metal to reach the downstream concentration detector, and calculate the portion of the liquid metal detected by the downstream concentration detector.
By assuming that the area detected by the upstream concentration detector is the same, and finding the correlation between the detection signals detected by these detectors,
The structure is such that noise contained in each detector is removed to accurately detect the concentration of reaction products, and water leakage can be detected at an early stage.

[Embodiments of the invention]

A preferred embodiment of the liquid metal water leakage detection device according to the present invention will be described in detail with reference to the accompanying drawings. Note that the same reference numerals are given to the parts corresponding to the parts explained in the prior art, and the explanation thereof will be omitted.

FIG. 3 is an explanatory diagram of an embodiment of the liquid metal water leak detection device according to the present invention. In FIG. 3, the return pipe 18 is provided with a sodium flow meter 34.

This sodium flowmeter 34 is electrically connected to a delay time calculator 36. The detection r of the hydrogen detectors 30 and 32 is input to the soma function calculator 38 together with the output signal of the delay time calculator 36.

The operation of the embodiment configured as described above is as follows.

Regarding the sodium circulating in the secondary main cooling system, the amount of sodium flowing through the return pipe 18 is detected by the sodium flow meter 34, and the detection signal is input to the delay time calculator 36. The delay time calculator 36 calculates the flow rate of sodium flowing in the return pipe 18, calculates the time it takes for IJum to pass between the hydrogen detector 30 and the hydrogen detector 32, and calculates the flow rate of sodium flowing in the return pipe 18. 38.

The cross-correlation function calculator 38 takes in the hydrogen concentration detection signal X30D output from the hydrogen detector 30, and also takes in the hydrogen concentration detection signal X32D from the hydrogen detector 32.These concentration detection signals X30D+x3□ 0 is the concentration detection signal X3o, X3 that does not contain noise as shown in FIG.
2. Noise of each hydrogen detector 30.32 ■301 v32
are superimposed, and is expressed by the following equation.

X30D:X30+■30 1°'(1)X
3zo=X32+V32 °°(2
) These noises v30 + v32 have properties close to so-called white noise whose average value is zero. Therefore, hydrogen concentration detection signal X30D of hydrogen detector 30.32
The cross-correlation function φ+)3G+32(τ) of +X32D can be approximately expressed by the following equation.

φ30132 (τ) − φ30132 (τ)
(3) Here, φ3o, 3□(τ) represents the cross-correlation function of the noise-free hydrogen concentration detection signal x3G + X32, and τ represents the time difference between the two signals.

That is, by taking the cross-correlation of the concentration detection signals X30D'+X32D of the two hydrogen detectors 30.32 from equation (3), the unique noise v3G' of the hydrogen detectors 30.32 is calculated.
It can be seen that a signal with almost all +v32 removed is obtained.

On the other hand, when the hydrogen concentration of the sodium portion whose hydrogen concentration has been detected by the hydrogen detector 30 is detected by the hydrogen detector 32, a delay time τN exists. This τN is determined by the sodium flow rate Q in the secondary main cooling system, since the transfer time of IJum in the sampling tubes of the hydrogen detectors 30 and 32 is equal. Then, when the sodium volume between the two hydrogen detectors 30 and 32 of the stutter tube 18 is VN, τN can be determined by the following equation.

r N = V N / QN ”・(
4) Therefore, the sodium flow meter 34 installed in the return pipe 18
Determine ° sodium flow rate Q, and use delay time calculator 3.
Enter 6. Then, the delay time calculator 36 calculates the delay time τN, inputs it to the cross-correlation function calculator 38, and generates the hydrogen concentration detection signal X3 of the two hydrogen detectors 30°32.
By determining the value φ 30132 (τN) of the cross-correlation function of ゜D+X32D and determining its change over time, changes in the hydrogen concentration in sodium can be accurately determined.

Figure 5 shows the hydrogen detector 30.3 determined by the above method.
2 shows the time variation of the value φD3□0132 (τN) of the cross-correlation function for the hydrogen concentration detection signal X300 + X32D of No. 2. As is clear from the figure, φ 3
0+32(τN) has almost no noise compared to xsoo l X32D, and a signal with good sensitivity can be obtained. Therefore, leakage of water or water vapor into the sodium can be detected at an early stage.

〔Effect of the invention〕

As explained above, according to the present invention, the time delay with respect to the detection signals of a plurality of detectors for detecting reactive components between liquid metal and water in the liquid metal flowing through the pipe is determined, and the time delay from these detectors is calculated. By determining the correlation for the detected signal,
Leakage of water or water vapor into the liquid metal can be detected early.

[Brief explanation of drawings]

Figure 1 shows the installation position of the hydrogen detector in the secondary main cooling system of a sodium-cooled fast breeder reactor, Figure 2 shows the temporal change in the hydrogen concentration detection signal of the hydrogen detector, and Figure 3 4 is an explanatory diagram of an embodiment of the liquid metal water leak detection device according to the present invention, FIG. 4 is a diagram illustrating that the hydrogen concentration detector of the hydrogen detector includes noise, and FIG. FIG. 3 is a diagram showing temporal changes in the values of the calculated cross-correlation functions. 16... Transfer pipe, 18... Return pipe, 20... Steam generator, 22... Superheater, 24... Evaporator, 28,
30.32...Hydrogen detector, 34...Sodium flowmeter, 36...More 1 home 2 diagrams poem closed L No. 30

Claims (1)

[Claims] 1. In a water leak detection device for liquid metal, which has a pipe through which liquid metal circulates, and a plurality of concentration detectors installed along this pipe to detect the concentration of reaction products of the liquid metal and water or steam. , a flow rate detector that detects the flow rate of the liquid metal in the pipeline, a computing unit that calculates the travel time of the liquid metal between the concentration detectors based on the detection signal of the flow rate detector, and an upstream side a computer that calculates a correlation between the detection signal outputted by the concentration detector and the detection signal of the downstream concentration detector outputted after the output time of the concentration detector by the time determined by the calculator; A water leak detection device for liquid metal, characterized in that it is provided with.