JPS6140077B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ion detector capable of obtaining a sufficiently reliable leakage signal at the time of a minute leakage of metallic sodium, which is a coolant of a fast breeder reactor.

A conventional ion detector has a configuration shown in the principle diagram shown in FIG. 1. When sodium reaches a position close to the filament 11, it is ionized, and the ions are guided to the collector 13, and the presence of sodium is detected as an ionization current signal. It is now being detected as .

However, in this case, it is not possible to verify whether the detected signal is caused by sodium ions.
Therefore, no matter how sensitive an ion detector is, it is not possible to shut down a nuclear reactor just by relying on this signal.

To explain FIG. 1 in more detail, FIG. 1 schematically shows a conventional ion detector, in which 1 is the ion detector main body, a filament 11 and a collector 13.
A voltage is supplied between the two from the outside via an insulated terminal 12, and these are housed in a housing 14. The filament 11 is heated to about 1000℃, and the filament 11 and the collector 1
A voltage of several hundred volts is applied between the terminals 3 and 3. Therefore, if a substance that is easily ionized, such as sodium, which is the target substance in the gas to be detected, comes near the filament 11, it will be ionized, and the collector 1 will be ionized by the action of the electric field.
3 and detected as an ionization current signal.
Reference numeral 2 denotes a filter, which is a filter paper 21 held by a filter holder 22, and is used to collect sodium aerosol and the like. Then, the sodium aerosol etc. collected in this way is dissolved in a solvent,
The presence or absence of sodium is being investigated using atomic absorption spectroscopy.

The method of sodium verification currently being considered is based on the ion detector itself (hereinafter abbreviated as SID).
A filter placed in series or parallel (Figure 1 shows the case of series) is removed after the ion detection signal indicates a risk of leakage, and the presence or absence of sodium is confirmed using atomic absorption spectroscopy. be. However, since this method is not an online measurement and is entirely done manually, there are many problems such as time lag and S/N ratio, and it cannot be said to be the best method.

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and it detects the electrical resistance between two points on the paper of the filter, and also detects the electric resistance from the ion detection signal and resistance value detection signal of the ion detector body. By obtaining a highly reliable leakage signal, it is not possible to directly verify whether the ion detection signal of the ion detector body is due to sodium, but it is possible to determine whether the ion detection signal from the ion detector body is due to sodium or something else. An object of the present invention is to provide an ion detector that provides information that is easier to distinguish.

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

In FIG. 2, 1 is the same ion detector main body as shown in FIG. 1, and the filament 11, insulated terminal 12, collector 13, and housing 14 are also the same, and the operation is the same. 2 is a filter, and 2 is installed so that the resistance between two points on the filter paper 21 can be measured.
Two electrodes 23 are arranged in close contact with the filter paper 21. A lead wire 25 is connected to this electrode 23 and taken out to the outside through an insulated terminal 24. Although this lead wire 25 is not shown, it is connected to a constant voltage power source, and the resistance value can be determined from the flowing current.

In this device, two electrodes 23 are installed close to each other on the paper 21 of the filter 2, and the resistance value between them is measured to estimate the substance trapped on the paper 21.
By combining this information with the ion detection signal from the ion detector main body 1, a more accurate signal indicating whether or not it is sodium can be obtained. That is, it may be determined whether sodium is present or not depending on each situation as follows (see FIG. 3).

(a) If a signal is obtained with SID and the resistance on the filter has also moderately deteriorated, it is determined that sodium is likely to be present.

(b) If a signal is obtained with SID, but there is no change in the resistance of the filter, the leaked sodium may be extremely small, but this is a false signal from SID, so monitor the progress and move to (a). See if.

(c) If a small signal is obtained with SID and the resistance of the filter has significantly deteriorated, it is likely that it is not sodium but a floating object such as a metal piece.

(d) If you cannot get a SID signal and the resistance of the filter has deteriorated slightly, it is likely that airborne dust has collected, so it is better to replace the filter.

In this way, according to the present device, the filament 11
The ionization current signal of the SID consisting of the collector 13 and the resistance value signal on the filter 2 can be obtained simultaneously online, making it possible to more reliably detect the target substance such as sodium in the test gas.

In the above embodiment, the output signal of the ion detector body and the detection signal of the change in resistance value on the surface of the filter are combined to determine whether or not it is sodium. It may also be detected.

As described above, according to the present invention, the electrical resistance between two points on the paper of the filter is detected, and the reliability is determined from the ion detection signal and the resistance value detection signal of the ion detector main body, or only from the resistance value detection signal. Since a high detection signal of the target substance is obtained, it becomes easier to determine whether it is sodium or not, and the reliability can be improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a conventional ion detector, FIG. 2 is a schematic configuration diagram of an ion detector according to an embodiment of the present invention, and FIG. 3 is a detection signal of an ion detector according to an embodiment of the present invention. It is a figure which shows an example. 1...Ion detector main body, 2...Filter, 1
1...Filament, 13...Collector, 21...
...filter paper, 23...electrode.

Claims (1)

[Claims] 1. An ion detector body that is composed of a filament and a collector and outputs an ionization current signal generated by ionization of a target substance in a gas to be detected as an ion detection signal, and an ion detector body that is connected in series or parallel to this ion detector body and that is The ion detector body comprises a filter for trapping foreign matter containing the target substance in the sample gas, and two electrodes provided on the paper for detecting the electrical resistance value between two points on the paper of the filter. An ion detector characterized in that a highly reliable detection signal of the target substance is obtained from the ion detection signal and the resistance value detection signal or only from the detection signal.