JPS5934130A - Apparatus for processing detection signal of minute leakage of sodium in atomic power plant - Google Patents

Abstract

PURPOSE:To exclude an influence of noise etc. by integrating an output of Na ionization detector and sending out the detected output at the time when the number of times when the difference of this integrated output and its mean value has exceeded over a fixed value becomes a fixed value or more in the reference time. CONSTITUTION:An ionization detecting signal 21 of a Na ionization detector is integrated by an integrator 42 and is added to a decision circuit 42 and also, is added to an operator 44 operating the mean value. Further, the integrated output is discriminated from the mean output by the circuit 43 and ''1'' is set on a memory circuit 45 at the time when the integrated output has exceeded by a set point or more above the means value. The above-mentioned action is repeated periodically by a signal of a timing pulse generator 47 and (n) pieces of data of the circuit 45 are examined by a majority logic circuit 46 and then, a leakage decision output is outputted at the time when (m) pieces of data among (n) pieces of data is ''1''.

Description

[Detailed Description of the Invention] N,=1 detector and timing pulse generation circuit that detect sodium (hereinafter abbreviated as N and l in this specification) leaked from piping at a nuclear power plant by ionizing it. The signal from the Na detector described in - is integrated by the signal from the timing pulse generation circuit, and the output obtained in (7) is compared to the set value.
I1. This invention relates to a signal processing device for detecting minute Na leakage.

Liquid Na is used as a coolant for fast breeder reactors. Na
is chemically active, and Na leakage from equipment that makes up the Na-containing coolant boundary, pinholes in piping, cracks caused by thermal cycle fatigue, etc. can cause serious problems such as loss of reactor coolant and Na fires. There is a risk of developing into serious trouble.

In order to prevent the above-mentioned accidents from developing, the Na minute leak detection device quickly and reliably detects minute leaks that ooze out from cracks in pipes, etc., and is used to ensure the safety of the reactor. It is a device.

A method for detecting this minute leakage is referred to as a Na ionization detector (hereinafter referred to as SII).

) is commonly used. Figure 1 shows Na by SID.
A micro leakage detection device is shown. High-temperature Na is contained in a pipe 1, and a heat insulating material 2 is provided outside of the pipe 1. When a crack occurs in the pipe 1 and Na leaks, a portion of pJa evaporates in the annulus surrounded by the heat insulating material, generating Na aerosol. This Na aerosol is guided to the sampling pipe 3, set to a predetermined flow rate by the flow rate control valve 4, and sucked by the sampling pump 5 via the 5ID11.

This Na aerosol is ionized at 8ID11 and an ion current is output to the amplifier 12. The amplifier 12 converts the signal into an Na leak signal, the signal processing device 13 performs leakage determination, and outputs it to the display device 14 if necessary.

FIG. 2 shows a conventional technique of a signal processing device related to leakage determination. The Na leakage signal 21 is inputted to the signal processing device 13, is compared with a set value 23 by a comparator 22, and is output to the alarm device 14 if the set value is exceeded.

In the above method, it is difficult to distinguish the information from the actual Nam leakage information, and it is also difficult to determine the set value, due to the effects of changes in plant operating conditions, foreign matter contamination, etc., and changes in aerosol behavior. Therefore, there was a drawback that it did not function sufficiently, especially for the purpose of early accident detection and prevention of spillover.

FIG. 3 shows an example of a temporal change in the output signal from S.

In the figure, 1° indicates the point at which Na leakage occurs. A characteristic of the signal is that a sudden pulse-like signal appears even when there is no Na leakage. Therefore, in the case of the conventional level-based comparison method with a set value, a leakage signal is generated for a signal that exceeds the set level 31, such as the signal at time t'. Moreover, similar inconveniences occur when the background level fluctuates due to initial operating conditions. As described above, the conventional techniques cannot reliably determine leakage and are extremely unreliable.

An object of the present invention is to provide a signal processing device for a Na minute leak detector for quickly and reliably detecting Na minute leaks.

In order to achieve the above object, the N″a micro leakage detection signal processing device in a nuclear power plant according to the present invention of the type mentioned at the beginning is further provided with a majority logic circuit, and a long-term average value corresponding to the shoe sound level is The main idea is to apply majority logic to those whose difference from the reference value calculated from the reference value exceeds a predetermined value, confirm the continuation of that state, and discriminate between sudden pulse signals and signals due to noise fluctuations. shall be.

An embodiment of the present invention will be described below with reference to FIG.

The illustrated circuit includes an integrator 42 that takes in a signal (Si) 21 from S and performs an integral calculation, a determination circuit 43 that performs a comparison with a set value, a storage circuit 45 that stores the comparison result, and finally a leakage determination process. It is composed of a majority logic circuit 46 that determines the timing, a timing pulse generation circuit 47 that outputs periodic pulses, and an arithmetic unit 44 that calculates the reference value (Co), and calculates the integral value (Ci) from the output signal of the SID. As a result, the device is capable of effectively determining leakage in the case of a subtle increase in the signal after leakage, and can also prevent malfunctions in response to sudden pulse signals and background fluctuations.

S I I) signal (Si) 21 is transmitted for 30 seconds 4'T! by the signal from the timing pulse generator 47. degree interval (1
) into the integrator 42, as shown in the following equation? Calculate the 11 minute straightness (Ci).

By calculating the integral value (C1) of tゎ-1ll-1=, sudden pulse-like signals not caused by leakage can be removed. The integral value (C1) obtained by equation (1) is used for leakage determination and setting of the reference value (CO). In the leakage determination circuit 43, a comparison t11 is performed as shown in the following equation.

Ci>C8...(2) 0, i-CO,>CS
...(3) However, C1: integral value, C5: set value, C
O: Reference value.

Here, the set value (C3) is a value determined in advance based on the 5II) Buddhist name level. The reference value (CO) is +1.
It is the average value of the SID signal i~, - period before the current calculated integral value (C1), and is expressed by the following equation.

Normally, the reference value (CO) is almost constant in the state before leakage, and even in response to sudden pulse signals, it is a stable signal because it is averaged over a long period of time, and is equivalent to the average value of the background signal. are doing.

After Na leaks, as the leakage signal increases, the integral value (C1) increases and exceeds the set value (C5) (2)
When the condition of the equation is satisfied and the value obtained by subtracting the background from the integral value (Ci) exceeds the set value (C8), the leakage judgment pulse is output and the initial state is All memory circuits 45 were set to 'O'.
Put up a @ 1 # flag. If not, ′
It becomes 0#.

Since data is sequentially stored in the determination circuit 45, leakage determination is always performed on n pieces of data, and if m flags out of n are '1', the majority logic circuit for leakage determination A leakage judgment output 48 is outputted via 46. In other words, S monitors the sudden pulse waveform of the signal and the irregularity of repeated increases and decreases for the minimum amount of time that allows a reliable leakage judgment to be made. The system is designed to prevent malfunctions caused by hasty judgments.

FIG. 5 shows a time chart of this signal processing device. S.I.
Integral values (C1) are sequentially calculated for the D signal (Si) using timing pulses. Usually, S before Na leakage
Although the ID signal (Si) 21 suddenly outputs a signal,
The background signal is at a certain level, and there are no large level fluctuations.

Therefore, equations (2) and (3) are not satisfied consecutively. However, after the Na leakage point shown by, a subtle but significant signal appears with respect to the background signal and continues, so that when the integral value (C1) satisfies equations (2) and (3), A leak determination flag is raised and the majority logic circuit 46 operates, thereby producing a leak determination output 48.

As mentioned above, the integral value is calculated as a signal processing method for the SID signal] 2. By comparing with the set value, it is possible to detect subtle changes in the signal level, which is a feature of the SID signal.
It is possible to prevent erroneous QB operation even in response to sudden signals, and also to remove background level signals that depend on the initial state of the plant, thereby also removing the influence of the background. In particular, even if the leakage Na stitch is 4f'7'FN and the SID signal rises only slightly, the integral comparison method can capture the subtle increase by taking the average increment of the signal, and the leakage is sufficient. Able to make judgments.

Therefore, the reliability of the Na microleakage detection system is greatly improved compared to the conventional technology. Furthermore, no--
The software configuration and L7 can be realized with one microprocessor or the like, and are fully practical.

As has been explained and clarified above, according to the present invention, SID signals can be handled quantitatively, and conventional SID signals can be used to determine leakage based only on level fluctuations. By using this system and performing signal processing, the leak detection system can be used to determine leakage, and the reliability of the system can be improved.

Very dog-like.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a conventional SID-based Na2 small liter leak detection device, Fig. 2 is an explanatory diagram of a conventional Iba processing device for leak detection, and Fig. 3 is a block diagram of a conventional SID-based Na2 small liter leak detection device.
Block 1 and block 51 of the signal processing device for leakage determination according to the present invention are A' in the time chart of the device shown in FIG. 1...' Piping, 2... Heat insulating material, 3... Sampling arrangement ~ f, 4... Flow control valve, Sampling valve, 11... 8 ID detector, 12...・・Masu 11i
? l equipment, 13...(K coping J!
ID signal (Na leakage signal t), 22... comparator,
42... Integrator, 43...'I'41 Constant circuit, 44
. . . Arithmetic unit, 45 . . . Memory circuit, 46 . . . 101 majority logic circuits, 47 .

Claims (1)

[Claims] 1. A sodium detector and a timing pulse generation circuit are provided, which detect sodium leaked from piping at a nuclear power plant by ionizing it, and the signal from the sodium detector is transmitted to the timing pulse generation circuit. In the sodium microleak detection device, which integrates the signal from [therefore] and compares the output thus obtained with a set value, a majority logic circuit is further provided, and a reference value obtained from a long-term average value corresponding to the noise level is provided. It is characterized by applying majority logic to those whose difference from the value exceeds a predetermined value, confirming the continuation of that state, and discriminating between sudden pulse signals and signals due to noise fluctuations.
Signal processing device for detecting small sodium leaks in nuclear power plants.