JP2001153956A - Apparatus for measuring radioactivity concentration of gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus for measuring the radioactivity concentration of gas continuously and having a wide sensitivity in which increase of measurement value is suppressed even for a high radioactivity concentration only with a low range monitor. SOLUTION: In order to suppress increase in the measurement value of an apparatus for measuring radioactivity concentration of gas, radioactivity quantity being brought to a gas measuring container 7 is limited utilizing the fact that the radioactivity quantity is proportional to the measurement value. The inventive apparatus for measuring radioactivity concentration of gas is provided with a gas measuring container 13 of different capacity. Furthermore, a purge line for replacing with clean air is provided in order to eliminate the effect of background radiation due to radioactive substances brought into a measuring container on the non-measuring side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas radioactivity concentration measuring device for monitoring radiation in a nuclear facility or the like.

[0002]

2. Description of the Related Art As a device for measuring the concentration of gaseous radioactivity in a nuclear power plant, a method has been adopted in which radiation is continuously measured by a radiation detector installed in a measurement container and the radiation level is indicated and recorded. I have. Using a gas radioactivity concentration measurement device to detect an increase in radioactive materials,
In order to evaluate the effects of radiation on the environment, it is important to accurately measure a measurement range from a minute radioactivity concentration to a high radioactivity concentration.

[0003] As a known example of a gas radioactivity concentration measuring device which has solved such a problem, Japanese Patent Laid-Open No. 10-200040 is known.
In general, detectors and measurement containers with different measurement ranges are installed and measurement is performed with high accuracy.

[0004] In addition, as another disclosed example, as disclosed in JP-A-53-142283, by controlling the pressure of gas in a measurement container and compressing and diluting gas radioactivity in the measurement container. There is a gas radioactivity concentration measurement device that expands the measurement range.

[0005]

An exhaust gas monitor, which is one of the gas radioactivity concentration measuring devices of a nuclear power plant, continuously monitors a low range monitor and a high range monitor for radiation from a rare gas in respective measurement vessels. Since two types of detectors are used for measurement, separate measurement containers are required.

Further, a method as disclosed in Japanese Patent Application Laid-Open No. Sho 53-142283 has been proposed. This method can expand the measurement range with one detector, but is not suitable for continuous monitoring because of intermittent measurement. .

Accordingly, an object of the present invention is to provide a gas radioactivity concentration measuring device capable of continuous measurement with a wide range of sensitivity in which an increase in the measured value is suppressed even at a high radioactivity concentration using only a low range monitor.

[0008]

According to the present invention, in order to suppress an increase in the measured value of the gas radioactivity concentration measuring device, the radioactivity is taken into the gas measuring container by utilizing the fact that the radioactivity is proportional to the measured value. Shall be restricted. For this reason,
The gas radioactivity concentration measurement device of the present invention is provided with gas measurement containers having different capacities.

In addition, a purge line is provided for purging with a clean gas in order to eliminate the influence of background radiation from radioactivity brought into the non-measurement side gas measurement container.

According to a first aspect of the present invention, there is provided a process pipe, a sampling pipe connected to the process pipe, a gas radioactivity concentration measuring vessel disposed in the middle of the sampling pipe, and monitoring radiation of the measuring vessel. In those equipped with a signal processing unit for displaying a radiation detector and an instruction alarm,
A measurement container for high concentration measurement is provided at the lower end of the measurement container,
A valve switching signal generator connected to the signal processor, a pipe for replacing the measurement container with a non-radioactive gas, and a valve that opens and closes with a valve switching signal are provided.

[0011]

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

FIG. 1 shows an embodiment of the present invention. The radioactive gas in the process pipe 1 passes through the sampling pipe 2 connected to the process pipe 1, passes through the low-concentration measuring vessel 7 installed in the sampling pipe 2, and then passes through the low-concentration measuring vessel 7.
Is returned to the process pipe 1 from the sample pump 12 connected downstream. The radioactive gas guided to the low-concentration measurement container 7 is continuously measured by the radiation detector 7, and its signal is indicated and recorded by the signal processing unit 10. The present invention includes a measurement container 13 for measuring high concentration at the lower end of the low concentration measurement container 7,
The purge filter 5 and the purge air inlet valve 4 are connected to the sampling pipe 2 at the inlet of the measurement container, and a non-radioactive gas is supplied to the measurement container. A low-concentration measurement container inlet / outlet valve 6 that opens and closes by a valve switching signal at an entrance / exit pipe of the low-concentration measurement container 7 and a high-concentration measurement container entrance / exit valve 12 that opens and closes by a valve switching signal at an entrance / exit pipe of the high-concentration measurement container 13 are attached. A valve switching signal generating section for operating the valve according to a measurement level of a detector connected to the section is provided.

FIG. 1 shows an operation state of low radioactivity measurement in a normal state. The radioactive gas in the process pipe 1 flows into the low-concentration measurement container 7 from the sample inlet valve 3 and the low-concentration measurement container inlet valve 6 and is measured by the radiation detector 7. When the radioactivity concentration of the radioactive gas increases and the measured value is determined by the signal processing unit 10 and approaches the upper limit of the measurement, the valve switching signal generating unit 14 outputs an open signal of the purge air inlet valve 4 and further the sample inlet valve 3.
And a non-radioactive gas is introduced into the low-concentration measurement container 7. After the gas replacement of the measurement container is completed, the high-concentration measurement container inlet / outlet valve 12 is opened, the low-concentration measurement container inlet valve 6 is closed, and the sampling flow path is switched.
And the purge air inlet valve 4 is closed to stop purging. The highly radioactive gas in the process pipe is introduced into the high-concentration measurement container 13 and the measurement can be continued by the radiation detector 7.
Thus, it can be expected that the residual radioactive gas in the low-concentration measurement container 7 is replaced with the non-radioactive gas, and the background radiation due to the residual radioactivity is eliminated. Further, when the gas returns to the low radioactivity level, when the radioactivity of the radioactive gas decreases and the measured value is determined by the signal processing unit 10 and approaches the measurement lower limit, the valve switching signal generation unit 14 outputs the above-described valve. Is issued to bring the state shown in FIG. As a result, the measurement range can be expanded and the measurement accuracy can be improved.

In this embodiment, the measuring unit is a container.
Simpler piping is also possible.

In this embodiment, the clean air is introduced into the measuring container by the purge filter. However, a configuration using a nonradiative gas such as a gas cylinder is also effective.

In this embodiment, two measuring vessels and one detector are shown. However, a plurality of measuring vessels and a plurality of detectors may be installed, and a pipe or vessel may be provided in the measuring vessel. It is also possible to adopt a structure in which is inserted.

[0017]

In the gas radioactivity concentration measuring device constructed as described above, the residual radioactive gas in the high / low concentration measurement container is replaced with a non-radioactive gas and background radiation due to the residual radioactivity is eliminated. be able to. further,
By providing measurement containers having different detection sensitivities, the concentration measurement range of the gas radioactivity concentration measurement device can be expanded.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of a system configuration of a gas radioactivity concentration measuring device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Process piping, 2 ... Sampling piping, 3 ... Sample inlet valve, 4 ... Purge air inlet valve, 5 ... Purge filter, 6 ... Low concentration measurement container inlet / outlet valve, 7 ... Low concentration measurement container, 8 ... Shielding material, 9 ... Radiation detector, 10 ... Signal processing unit, 11 ... Sample pump, 12 ... High-concentration measurement container inlet / outlet valve, 13 ... High-concentration measurement container, 14 ... Valve switching signal generation unit.

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Claims (1)

[Claims] 1. A process pipe, a sampling pipe connected to the process pipe, a gas radioactivity concentration measurement vessel connected in the middle of the sampling pipe, and radiation for monitoring radiation of the gas radioactivity measurement vessel. A detector provided with a signal processing unit for displaying an instruction and an alarm, wherein a measurement container for high concentration measurement is provided at a lower end of the measurement container, and a valve switching signal generation unit connected to the signal processing unit and the measurement container are connected to a non-radioactive gas. 1. A gas radioactivity concentration measuring device, comprising: a replacement pipe, a purge valve operated by a valve switching signal, and a measurement container inlet / outlet valve.