JPS59125087A - Radiant ray detecting device - Google Patents

Abstract

PURPOSE:To obtain a radiant ray detecting device which can save remarkably a gas consumption by disposing a counting gas refiner for eliminating an impure component in counting gas, on the counting gas leading-in side of a gas flow counter. CONSTITUTION:The counting gas supplied to the gas flow counter train consisting of (m) pieces of cascaded gas flow counters 51, 52... 5m, through an opening and closing valve 2, a pressure regulator 3 and a flow meter 4 from a counting gas cylinder 1 is discharged into the air through a check valve 6. In this case, the counting gas refiners 71, 72...7m are inserted and disposed at the gas inflow side of each gas flow counter respectively. When Q gas is used as the counting gas, it obtains a prescribed characteristic of the gas flow counter, therefore, water in the Q gas which is transmitted a radiant ray incident window 21 is eliminated from the Q gas by the characteristic difference of a boiling point, etc., the transmission of the water by a semipermeable member or a gas refiner utilizing an adsorption, etc. In this way, it becomes unnecessary to flow more gas quantity than the gas quantity operating effectively for counting a radiant ray, in order to reduce the impure component density in the counting gas, and the counting gas can be saved remarkably.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a radiation detection device that detects radiation by supplying counting gas to a gas flow counter.

A method of detecting radiation by supplying counting gas to a gas flow counter at a pressure slightly higher than atmospheric pressure is known. This method is widely used as a GM counter (Geiger-Mueller counter) or a proportional counter by changing the type of counting gas supplied. There are various types of counting gas, but generally PR gas (argon about 90%, methane about 10%
%) and Q gas (helium approx. 99%, imbutane approx. 1%)
It is often used to reduce the pressure from a counting gas cylinder to a predetermined pressure and supply it to a gas flow counter.

FIG. 1 shows a typical configuration example of this type of radiation detection device.

In the apparatus shown in FIG. 1, the counting gas is guided from the counting gas cylinder 1 through the on-off valve 2 to the pressure regulator 3, where it is reduced to a predetermined pressure, and further adjusted to a predetermined flow rate by the flow meter 4. m cascaded gas flow counters 5I
It flows through a gas flow counter array of ~5 m and is discharged into the atmosphere via an atmospheric backflow preventer 6. The flow meter 4 may be placed at any point in the gas flow path, and may be placed after the gas flow counter row, for example, as shown by the broken line.

FIG. 2 shows an example of a configuration in which a plurality of gas flow counter rows are provided in parallel. In this case, pressure regulator 3
A gas branching pipe 7 is provided on the outlet side of the meter, and the counting gas is branched here, and the flowmeter 41 gas 70-counter 5,1 to 5II,
From the first channel consisting of l and atmospheric backflow preventer 61, flowmeter 4n) gas flow counter 5°1-5
It is supplied in parallel to n systems up to the n-th channel consisting of the air flow prevention device 6n and the atmospheric backflow preventer 6n. Again, flowmeter 4I
~4n may be arranged on the gas outlet side of the gas flow counter array as shown by the broken line.

In a radiation detection device configured in this way, unless the counting gas is supplied in excess of the amount of gas effectively used for radiation measurement, the performance of the gas flow counter will reach a stable plateau, as shown in Figure 3. I can't get the curve. Incidentally, in Fig. 3, the horizontal axis is the applied voltage of the detector,
The vertical axis is the count rate value, the curve KP shown by a solid line is a stable Plato curve obtained when a sufficient amount of counting gas is supplied, and the curve KQ shown by a broken line is a Plato curve obtained when the amount of counting gas supplied is insufficient. . Therefore, this type of device has the disadvantage that unused counting gas is not released into the atmosphere, requires a large amount of counting gas, and increases the operating cost of the device.

Generally, the maximum radiation count that can be counted without changing the properties of the counting gas is about 108 to 1010 counts/cc, but in the above-mentioned apparatus it is about 103 to 105 counts/cc. Therefore, there is a drawback that as the number of gas flow counter arrays increases, the gas flow rate also increases.

Therefore, in order to save the amount of counting gas used, a gas circulation system shown in FIG. 4 has been proposed. After the counting gas discharged from the counting gas cylinder 1 flows through each gas flow counter row in the same way as in the above-mentioned device, a part of it is released into the atmosphere from the atmospheric backflow preventer 6 3) Then, the remaining gas is counted. The gas is pressurized by the resistance tube 10 via the gas purity monitor 8 and the circulation pump 9, and after receiving replenishment from the counting gas cylinder 1 for the amount of gas released into the atmosphere, that is, the amount of gas lost, the gas is transferred to the gas flow counter array. returned and reused. A gas purity monitor 8 monitors the purity of the counted gas returned for reuse, and if the purity falls below a predetermined value, a solenoid valve 12 provided at the gas discharge point, and The solenoid valve 13 installed in series with the pressure regulator 3 is opened to discharge a large amount of gas with reduced purity and to supply new counting gas to maintain the gas purity in the device above a predetermined value. .

However, in the gas circulation system shown in Figure 4, if the gas purity in the gas circulation path decreases, the gas in the device must be replaced, so the amount of gas supplied during gas circulation must be replaced.
Approximately 0 to 12 times the amount of gas must be supplied. Therefore, the amount of counting gas saved is only about 10 to 20% compared to the non-circulating type. Further, in the system shown in FIG. 4, even if the number of gas flow counters increases, a significant saving effect does not occur. It's not just that, when operating in ρ-°, circulation mode, environmental changes occur (-%f), the purity of the counted gas in the device decreases, and while this is being replaced, the gas flow counter operates. There is also the disadvantage that the gas purity monitor becomes insufficient.To prevent this, increasing the setting value of the gas purity monitor
The amount of gas used increases and there is little savings in gas usage.

As a result of researching various ways to reduce the amount of counting gas used, the following discovery was made, and it became clear that unless this was removed, it was impossible to save the amount of gas used in any device. That is, as shown in FIG. 5, an anode line is insulated and stretched by an insulating bushing 24 in a metal container 22 having a radiation entrance window 21, a counting gas is passed through the container 22, and the main body of the container 220 is used as a cathode. A high voltage is applied between this and the anode ray device, and the radiation incidence window 2J of the gas flow counter is configured to count the radiation that enters the container 22 through the radiation incidence window 2J. In order to improve the radiation incidence and expand the radiation incident area, a thin organic film was used, but the discovery was made that the gas components in the dog air that permeated through this film interfered with counting gas savings.

Generally, when the proportion of the gas transmitted through the radiation entrance window 21 exceeds about 0.1% of the counted gas, the performance of the gas flow counter becomes the Plato curve KQ of insufficient gas supply, as shown in Figure 3. . For this reason, it has been found that the counting gas cannot be saved unless impure gas (gas transmitted through the radiation entrance window 21) in the counting gas is removed.

An object of the present invention is to eliminate the drawbacks of the radiation detection apparatus described above and to provide a radiation detection apparatus that can significantly reduce the amount of gas used. - In order to achieve this object, the present invention is characterized in that a counting gas purifier for removing impurity components in the counting gas is disposed on the counting gas introduction side of the gas flow counter.

FIG. 6 shows an embodiment of the present invention, and the present invention will be explained in further detail based on this figure. Figure 6 shows the counting gas cylinder 1, opening/closing valve 2, pressure regulator 3,
The counting gas is supplied via the flow meter 4 to a gas flow counter row consisting of m cascaded gas flow counters 5□, 52...5rQ, and the counting gas leaving the gas flow counter row is This shows an embodiment in which the present invention is applied to a non-circulating type gas discharged into the atmosphere via an atmospheric backflow preventer 6, and its feature is that each gas flow counter has a counter on the gas inflow side. Gas purifier 71+7
2...7o is inserted and arranged. Counting gas purifier7. , 72...7m are of course intended to remove impurity components from the counting gas passing through them. The present invention is of course applicable to a gas circulation type as shown in FIG. Further, it is not necessary to provide a counting gas purifier for every gas 70-counter, but for every several gas flow counters, for example, as shown in FIG.
One counting gas purifier 71 is provided for 5, 2...51m, and generally one counting gas purifier 71 is provided for each n-th set of m gas flow counters 5n1, 5na...5om.
It is also possible to provide several counting gas purifiers 7n. In any case, the flow meter 4 may be provided on the gas outflow side of the gas flow counter array as shown by the broken line, as in the case of the conventional device.

Next, a specific example of the gas purifier used in the present invention will be described in which Q gas is used as the counting gas.

When using Q gas as the counting gas, in order to obtain the predetermined characteristics of the gas flow counter, the radiation entrance window 21 (
It is important to remove the moisture contained in the Q gas that has permeated through the Q gas (Fig. 5). Therefore, the water contained in Q gas is
Gas purifiers that utilize differences in physicochemical properties such as the boiling point difference between the components contained in gas and water, or gas purifiers that utilize moisture permeation through a semi-permeable membrane, or gas purifiers that utilize adsorption phenomena. It is removed from Q gas by a purifier or the like.

By sufficiently removing impurity components in the counting gas in this way, it is possible to flow more gas than the amount of gas that effectively affects radiation counting in order to lower the concentration of impurity components in the counting gas. This eliminates the need for this, allowing for significant savings in counting gas. It goes without saying that the present invention is effective not only when Q gas is used as the counting gas, but also when using other counting gases.

As described above, according to the present invention, by arranging the counting gas purifier on the counting gas introduction side of the gas flow 7 counter, counting gas can be significantly saved.

[Brief explanation of drawings]

Figures 1, 2, and 4 are system diagrams showing different configuration examples of conventional radiation detection devices, Figure 3 is an explanatory diagram of the Plato curve in a gas flow counter, and Figure 5 is a schematic diagram of the gas flow counter. A vertical cross-sectional view showing the configuration, and FIGS. 6 and 7 are system diagrams showing different embodiments of the present invention. 1... Counting gas cylinder, 3... Pressure regulator, 4
...Flowmeter, 5.Gas flow counter, 6.
... Atmospheric backflow preventer, 7... Counting gas purifier. Paper fan

Claims (1)

[Scope of Claims] (1) In a radiation detection device that detects radiation by supplying a counting gas to a gas flow counter, a counting gas purifier that removes impurity components in the counting gas is provided on the counting gas introduction side of the gas flow counter. A radiation detection device characterized by arranging. (2. The radiation detection device according to claim 1, wherein a counting gas purifier is provided for each gas flow counter. (3) The radiation detection device according to claim 1. A radiation detection device characterized in that a counting gas purifier is provided for each of the plurality of gas flow counters.