JPS6058426B2 - Low concentration gas radioactivity measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a measuring device that can measure the amount of gaseous radioactivity online in a low concentration region.

In equipment that separates and concentrates krypton gas and measures the gas using a beta-ray or gamma-ray detector, even if the amount of radioactivity in the sampled gas is constant, the counts on the radiation detector will change due to fluctuations in the concentration rate. .

Therefore, it was necessary to constantly monitor the concentration rate in the concentrator and correct the counted value based on that value. However, in the past, there was no way to accurately determine the concentration ratio online, and the only way to do so was to rely on periodic calibration.

The present invention has been made in view of the above circumstances, and the concentration ratio in the membrane concentrator is obtained by processing the oxygen concentration with a calculator, and the value is used to measure the separated and concentrated gas with a radiation detector measuring device. By correcting the calculated value,
This allows the inlet concentration to be displayed accurately.
The details of the present invention will be explained below with reference to FIG. 1 showing one embodiment of the present invention. Air is sucked in through a sampling nozzle using a pump 14, and the oxygen concentration in the air is measured by an oxygen concentration meter 3a in the previous stage. and measure.

The concentration rate of the membrane concentrator 1 that separates and concentrates the sampling gas is determined by measuring the concentration of krypton gas in the front and rear stages,
It can be determined by the ratio, but if the inlet concentration is low, measurement is impossible.

However, if the permeable membrane of the membrane concentrator 1 is made of silicone rubber, for example, its permeability coefficient for krypton gas will be ~8 x 10-6 cc-c! rl/Cll・Sec・At
~4×10-6cc for ml oxygen CTn/Crl
●Sec◆Atm, it is possible to selectively separate and concentrate krypton gas and oxygen at a fixed ratio. Therefore, the oxygen concentration in the separated and concentrated gas, which can be easily measured, is measured using the oxygen concentration meter 3b in the subsequent stage. The relationship between the oxygen concentration in the separated and concentrated gas and the krypton gas concentration rate can be determined, for example, by configuring the membrane concentrator 1 with first and second cells 1a and 1b connected in series as shown in FIG. , if the gas that has permeated through the permeable membrane 15 of the second cell 1b is returned to the front stage of the pump 14, and the separated and concentrated gas that has permeated through the permeable membrane 16 of the first cell 1a is taken out, 1
When the sample gas at atmospheric pressure is pressurized to 6 atmospheres by the pump 14, the cut 01 of the first cell 1a is 0.01, and the cut θ2 of the second cell 1b is 0.08, the relationship shown by curve A in FIG. 3 is obtained. However, under the same conditions, the cut θ, of the first cell 1a is set to 0.
．． 02, when the cut θ2 of the second cell 1b is set to 0.09, the relationship shown by curve B is obtained.

Therefore, based on the relationship shown in FIG. 3, the first computing unit 12 calculates the concentration of krypton gas from the oxygen concentration in the separated and concentrated gas measured by the oxygen concentration meter 3b and the oxygen concentration measured by the oxygen concentration meter 3a. Calculate the rate. On the other hand, krypton gas separated and concentrated by the membrane concentrator 1 is introduced into a radiation detector 2 for detecting beta rays and detected.

A high voltage of about 1500 V is applied to this radiation detector 2 from a high voltage power supply 4 via a preamplifier 5 to obtain a signal. The preamplifier 5 converts the charge into a voltage pulse, and the main amplifier 6 connected to the preamplifier 5 amplifies the voltage pulse. In order to measure the amplified pulses, a discriminator 8 connected to the main amplifier 6 shapes the waveform to remove noise, and the pulse is introduced into a counter 10 or a rate meter 9 for measurement.

Arithmetic unit 12, counter 10 or rate meter 9 in FIG.
A second computing unit 11 connected to the processing unit 11 processes the concentration rate determined by the first computing unit 12 and the measurement value measured by the counter 10 or the rate meter 9 so as to obtain the inlet concentration, It is introduced into the display device 13.

As is clear from the above, according to the present invention, even if the concentration of the sampling gas changes and the concentration rate fluctuates, the inlet concentration can be accurately determined online, so it has great practical value.

Note that if the separation and concentration conditions of the membrane concentrator are constant, the concentration rate of krypton gas can be calculated simply by measuring the oxygen concentration with the oxygen concentration meter in the previous stage.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of a low concentration gas radioactivity measuring device according to the present invention, Fig. 2 is a diagram showing an example of a membrane concentrator, and Fig. 3 is a diagram showing the relationship between oxygen concentration and krypton concentration rate. . 1... Membrane concentrator, 2... Radiation detector, 3...
Oxygen concentration meter, 4... High voltage power supply, 5, 6... Amplifier,
8... Discriminator, 9... Route meter, 1
0... Counter, 11... First computing unit, 12...
Second arithmetic unit, 13...display unit.

Claims (1)

[Claims] 1. A membrane concentrator that separates and concentrates the supplied sampling gas, a measuring device that measures the oxygen concentration at the front stage of the membrane concentrator, or at the front and rear stages of the membrane concentrator, and a measuring device that measures the radioactivity of the gas separated and concentrated by the membrane concentrator. A radiation detector to detect, a measuring device to measure the radioactivity detected by the radiation detector, and a concentration ratio of the gas separated and concentrated by the membrane concentrator from the oxygen concentration measured by the measuring device. a first computing unit; a second computing unit that corrects the concentration ratio calculated by the first computing unit and the measured value obtained from the measuring device to the inlet concentration; 1. A low-concentration gas radioactivity measurement device comprising: a display device that displays corrected numerical values.