JPH1164527A - Gas monitor and water monitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas monitor and a water monitor capable of ensuring a desired calibration constant by one prototype and capable of supporting a plurality of ranges. SOLUTION: A gas sampler 1a comprises a height-adjustable chamber 13a, a radiation detecting part disposed thereunder and made up of a plastic scintillator 21, a light guide 22 made of acrylic resin, a photomultiplier 23, and the like and an inlet pipe 11 as well as an outlet pipe 12 for exhaust gas. The chamber 13a is formed of a movable wall 14 which moves while contacting airtightly with guide walls 17 via an O-ring 15 and of the plastic scintillator 21, and the movable wall 14 is moved by vertical driving of a drive shaft 16, causing volume of the chamber 13a to be adjusted and thus a calibration constant is adjusted. The gas sampler serves as a water sampler if waste water is led therein.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas monitor and a water monitor for continuously measuring, monitoring and recording radiation from radioactive isotopes present in exhaust gas or wastewater discharged from facilities such as nuclear power plants. About.

[0002]

2. Description of the Related Art In a conventional gas monitor or water monitor, a chamber for introducing exhaust gas or wastewater for measuring radiation from radioisotopes existing in exhaust gas or wastewater with a radiation detector has a fixed shape. FIGS. 3 and 4 show examples of a gas sampler 1 and a water sampler 3 as radiation detection units used in a conventional gas monitor and water monitor, respectively.

The conventional gas sampler 1 shown in FIG. 3 has a flat circular chamber 13 having a height of 30 mm and a diameter of 150 mm, for example.
A radiation detecting section including a plastic scintillator 21 having a thickness of, for example, 0.5 mm, a light guide 22 made of acrylic resin, a photomultiplier tube 23, etc.
It comprises an inlet pipe 11 for introducing exhaust gas to 13 and an outlet pipe 12 for discharging exhaust gas from the chamber 13. This shape is intended for detection of β-rays.

The light guide 22 holds the plastic scintillator 21 and simultaneously guides the light emitted by the plastic scintillator 21 to the photomultiplier 23. FIG.
In the conventional water sampler 3 shown in FIG. 1, a chamber 33 is arranged around a radiation detector 41 such as an ionization chamber or a scintillator using NaI (Tl) crystal. An outlet pipe 32 for discharging wastewater from the chamber 33 is provided, and the periphery of the chamber 33 is surrounded by a lead shield 51. This shape is intended to detect γ-rays.

[0005] A water sampler can be obtained by introducing wastewater into the gas sampler 1 , or a gas sampler can be obtained by introducing exhaust gas into the water sampler 3 . In a conventional gas sampler having a fixed chamber volume, in order to introduce a sample gas having a predetermined detection gas concentration and obtain a desired count number (to secure a desired calibration constant), the chamber is required to be trial and error. It is necessary to repeat prototypes with different dimensions, which requires much time and cost for development. For models with different measurement ranges, it is necessary to repeat the same prototype. This situation is the same for the water sampler.

[0006] The desired calibration constant is determined from the minimum count required to secure the required measurement accuracy and the condition that the count is not saturated in the highest detected gas concentration region.

[0007]

The object of the present invention is to provide:
It is an object of the present invention to provide a gas monitor and a water monitor which can secure a desired calibration constant by trial production and can cope with a plurality of ranges.

[0008]

SUMMARY OF THE INVENTION According to the present invention, in order to continuously measure, monitor, and record radiation from radioisotopes present in exhaust gas discharged from a facility such as a nuclear power plant, a measured object is measured. In a gas monitor including a chamber for introducing exhaust gas and a radiation detector provided adjacent to the chamber, a means for adjusting the volume of the chamber for introducing the exhaust gas to be measured is provided.

Since the means for adjusting the volume of the chamber is provided, the volume of the chamber can be adjusted and the amount of exhaust gas that can be introduced can be adjusted. Further, the means for adjusting the volume of the chamber includes a movable wall opposed to the radiation incident surface of the radiation detector, a cylindrical chamber side wall for sliding the movable wall in an airtight manner, and a space between the movable wall and the chamber side wall. It is composed of a means for maintaining airtightness and a driving means for the movable wall.

Since the volume of the chamber is adjusted by moving the movable wall facing the radiation incident surface of the radiation detector, radiation from exhaust gas in the chamber can be detected efficiently. In addition, in order to continuously measure, monitor, and record radiation from radioisotopes present in wastewater discharged from facilities such as nuclear power plants, a chamber for introducing the wastewater to be measured, and a chamber adjacent to this chamber are provided. In a water monitor provided with a radiation detector provided, a means for adjusting a volume of a chamber for introducing a wastewater to be measured is provided.

Since the means for adjusting the volume of the chamber is provided, the volume of the chamber can be adjusted and the amount of wastewater that can be introduced can be adjusted as in the case of the gas monitor. Further, the means for adjusting the volume of the chamber includes a movable wall opposed to the radiation incident surface of the radiation detector, a cylindrical chamber side wall for sliding the movable wall in an airtight manner, and a space between the movable wall and the chamber side wall. It is composed of a means for maintaining airtightness and a driving means for the movable wall.

Since the volume of the chamber is adjusted by moving the movable wall facing the radiation incident surface of the radiation detector, the radiation from the wastewater in the chamber can be detected efficiently.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The point of the present invention is that the volume of a chamber into which exhaust gas or waste water as a sample is introduced can be adjusted by moving a movable wall facing a radiation incidence surface of a radiation detector. . Hereinafter, embodiments of the present invention will be described. Note that the same reference numerals are used for portions having the same functions as in the case of the related art.

[First Embodiment] FIG. 1 is a partial sectional view showing the structure of a gas sampler 1a used in an embodiment of a gas monitor according to the present invention. A gas sampler 1a according to the present invention comprises a cylindrical chamber 13a of φ150 mm whose height can be adjusted, a plastic scintillator 21 having a thickness of, for example, 0.5 mm, a light guide 22 made of acrylic resin, and a photoelectron amplifier arranged on the lower surface thereof. It comprises a radiation detecting section composed of a multiplier 23 and the like, an inlet pipe 11 for introducing exhaust gas into the chamber 13a, and an outlet pipe 12 for discharging exhaust gas from the chamber 13a. The radiation to be detected by the gas sampler 1a having this structure is β-ray.

The light guide 22 holds the plastic scintillator 21 and simultaneously guides the light emitted by the plastic scintillator 21 to the photomultiplier tube 23. The cylindrical chamber 13a is formed by a cylindrical guide wall 17, a movable wall 14 that can move in an airtight manner by an O-ring 15 on the inner surface of the guide wall 17, and a plastic scintillator 21. The moving wall 14 moves up and down by moving the drive shaft 16 up and down by driving means (not shown),
Change the volume of 13a.

In this embodiment, since the volume of the chamber 13a is adjusted by moving the moving wall 14 parallel to the β-ray incidence surface of the plastic scintillator 21, the β-rays from the sample gas in the chamber 13a can be efficiently used. The calibration constant can be adjusted by entering the plastic scintillator 21 and adjusting the volume, and a desired calibration constant can be secured. Of course, if the target β-ray does not reach the plastic scintillator 21, the plastic scintillator 21 cannot detect the β-ray,
It is important to determine the moving range of the moving wall 14 according to the range of the β-ray.

Therefore, the gas sampler 1a according to this embodiment can be used as a water sampler, but in this case, the range of movement of the moving wall is greatly different since the range of β-rays is greatly shortened. It is necessary to consider things. According to this embodiment, since the volume of the chamber 13a can be adjusted, a desired calibration constant can be ensured at the time of actual gas calibration. Therefore, the expensive actual gas calibration can be performed only once, and it can be applied to a plurality of ranges.

FIG. 2 shows a second embodiment of the present invention.
The structure of the water sampler used in the embodiment of the water monitor
FIG. Water sampler according to the invention3a
Are used for ionization chambers and scintillators using NaI (Tl) crystals.
A chamber 33a is arranged around the radiation detector 41, and the
From the inlet pipe 31 and the chamber 33a that supply wastewater to the chamber 33a.
An outlet pipe 32 for discharging waste water is provided, and a chamber 33a is provided.
The periphery is surrounded by a lead shield 51. In addition, this structure
Water sampler3aIndicates that γ rays are to be detected.

The chamber 33a into which the drainage is introduced is formed in a cylindrical shape, and a moving wall 34 that can move along the inner wall of the chamber 33a is provided below the chamber 33a. O-ring set in the moving wall 34
Sealed airtight by 35. By moving the drive shaft 36 connected to the moving wall 34 up and down by driving means (not shown), the moving wall 34 moves up and down, and the volume of the chamber 33a is adjusted.

In this embodiment, the variable volume portion is provided at the lower portion of the chamber 33a, but a similar variable volume portion may be provided at the side surface of the chamber 33a. When the radiation to be detected is γ-rays, its range is large and there is little restriction on the distance to the detector. The calibration constant is determined by the size and shape of the radiation detector 41 and the volume and shape of the chamber 33a. . Therefore, it is desirable to determine the shape, number, and arrangement position of the volume variable portions according to the size of the adjustment range of the calibration constant.

Further, the water sampler 3a can be used as a gas sampler. Also according to this embodiment, the volume of the chamber 33a can be adjusted, so that a desired calibration constant can be ensured at the time of actual gas calibration. Therefore, the expensive actual gas calibration can be performed only once, and it can be applied to a plurality of ranges.

[0022]

According to the present invention, an exhaust gas to be measured is introduced in order to continuously measure, monitor and record radiation from radioisotopes present in the exhaust gas discharged from a facility such as a nuclear power plant. In a gas monitor including a chamber for performing measurement and a radiation detector provided adjacent to the chamber, the volume of the chamber for introducing the exhaust gas to be measured is provided. Thus, the amount of exhaust gas introduced into the chamber can be adjusted, a desired calibration constant can be secured by one trial production, and a plurality of ranges can be handled.

The means for adjusting the volume of the chamber includes a movable wall facing the radiation incident surface of the radiation detector, a cylindrical chamber side wall for sliding the movable wall in an airtight manner, and a space between the movable wall and the chamber side wall. Since it is composed of a means for maintaining airtightness and a driving means for the movable wall, radiation from exhaust gas in the chamber can be efficiently detected, and the effect of adjusting the volume of the chamber is efficiently exhibited. .

In order to continuously measure, monitor and record radiation from radioisotopes present in wastewater discharged from a facility such as a nuclear power plant, a chamber for introducing a wastewater to be measured, In a water monitor having a radiation detector provided adjacent to the water monitor, means for adjusting the volume of the chamber for introducing the wastewater to be measured is provided, so that the volume of the chamber is adjusted as in the case of the gas monitor. By doing so, the amount of wastewater introduced into the chamber can be adjusted, and a desired calibration constant can be ensured by one trial production, and it is possible to cope with a plurality of ranges.

The means for adjusting the volume of the chamber includes a movable wall facing the radiation incidence surface of the radiation detector, a cylindrical chamber side wall for sliding the movable wall in an airtight manner, and a space between the movable wall and the chamber side wall. Since it is composed of a means for maintaining airtightness and a driving means for the movable wall, radiation from drainage in the chamber can be detected efficiently, and the effect of adjusting the volume of the chamber is efficiently exhibited. .

[Brief description of the drawings]

FIG. 1 is a partial sectional view showing the structure of a gas sampler used in an embodiment of a gas monitor according to the present invention.

FIG. 2 is a partial sectional view showing the structure of a water sampler used in an embodiment of the water monitor according to the present invention.

FIG. 3 is a partial cross-sectional view showing the structure of a gas sampler used in an example of a conventional gas monitor.

FIG. 4 is a partial cross-sectional view showing the structure of a water sampler used in an example of a water monitor according to the related art.

[Description of Signs] 1 , 1a Gas sampler 11 Inlet tube 12 Outlet tube 13, 13a Chamber 14 Moving wall 15 O-ring 16 Drive shaft 17 Guide wall 21 Plastic scintillator 22 Light guide 23 Photomultiplier tube 3 , 3a Water sampler 31 Inlet Pipe 32 Outlet pipe 33, 33a Chamber 34 Moving wall 35 O-ring 41 Radiation detector 51 Lead shield

Claims (4)

[Claims] 1. A chamber for introducing an exhaust gas to be measured in order to continuously measure, monitor and record radiation from a radioisotope present in an exhaust gas discharged from a facility such as a nuclear power plant, and this chamber. 1. A gas monitor comprising: a radiation detector provided adjacent to a gas monitor; and a means for adjusting a volume of a chamber for introducing an exhaust gas to be measured. Means for adjusting the volume of the chamber includes a movable wall facing the radiation incident surface of the radiation detector, a cylindrical chamber side wall for sliding the movable wall in an airtight manner, a movable wall and a chamber side wall. 2. The gas monitor according to claim 1, wherein the gas monitor comprises means for maintaining airtightness between the two, and driving means for driving the movable wall. 3. A chamber for introducing a wastewater to be measured in order to continuously measure, monitor and record radiation from a radioisotope present in a wastewater discharged from a facility such as a nuclear power plant. 1. A water monitor comprising: a radiation detector provided adjacent to a water monitor; and a means for adjusting a volume of a chamber for introducing a wastewater to be measured. 4. A means for adjusting the volume of the chamber includes a movable wall facing the radiation incident surface of the radiation detector, a cylindrical chamber side wall for sliding the movable wall in an airtight manner, a movable wall and a chamber side wall. The water monitor according to claim 3, comprising means for maintaining airtightness between the two, and driving means for a movable wall.