JP3273850B2 - Portable radioactive surface contamination detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a portable radioactive surface contamination detector for measuring surface contamination by radioactive substances on the surface of an object.

[0002]

2. Description of the Related Art In nuclear power plants and facilities handling radioactive materials, radioactive surface contamination detectors are used to detect radioactive materials attached to the surface of workers and the like.

For example, a conventional radioactive surface contamination detector is:
Radiation such as α-rays and β-rays can be detected by a detection unit such as a GM tube or a plastic scintillator. When a GM tube is used for the detection unit, a pulse is output according to the dose of the radiation incident on the detection unit, and the detection of the radiation is performed by counting the pulses. Also,
When a plastic scintillator is used for the detection unit, radiation is detected by collecting light generated when the radiation is incident on the scintillator in a photomultiplier tube using a reflector or a light guide and measuring the amount of radiation. And
The degree of radiation contamination is determined and displayed based on the detected measurement value.

When measuring surface contamination by such a radioactive surface contamination detector, the detection section of the radioactive surface contamination detector is brought close to the surface of an object to be measured, such as an operator, and is sequentially scanned along the surface. This measures the radiation emitted from the radioactive material attached to the surface. And
The measured values are displayed on a meter or the like to indicate the degree of radiation contamination.

[0005]

However, the attenuation rate of radiation after being emitted from a radioactive substance differs depending on the type of radiation, and particularly, the attenuation rate of α-rays is large, and the radioactive substance may be attached. The measured value largely depends on the distance between the object to be measured and the detection unit of the radioactive surface contamination detector. In other words, even if the measured object in the same contaminated state is measured, the measured value differs between when measured close to the measured object and when measured a certain distance from the measured object. That is, there is a problem that the detection efficiency is different.

[0006] In particular, a measurer holds a radioactive surface contamination detector (a portable one is referred to as a survey meter) on an object to be measured such as a body surface or clothing having irregular irregularities on its surface. When measuring radioactive surface contamination by scanning along the surface of an object to be measured, it is difficult to keep the distance between the surface to be measured and the survey meter constant, and there is a problem that the detection efficiency varies greatly depending on the operator. .

[0007] Furthermore, the permissible pollution degree specified by law and the like is indicated by a value measured at a certain distance from the surface to be measured, so that the measured measured pollution degree can be directly compared with the permissible pollution degree. There was a problem that it could not be performed accurately.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has as its object to reduce the distance between an object to be measured and the detection unit of a radioactive surface contamination detector when the object has irregularities. It is an object of the present invention to provide a radioactive surface contamination detector capable of measuring radiation with a constant detection efficiency and displaying the degree of contamination even when the measurement person cannot be maintained and when the operator changes.

[0009]

In order to achieve the above object, the present invention provides a radiation measuring instrument for measuring radiation emitted from a radioactive substance attached to the surface of an object to be measured,
A distance detector for detecting a distance between the object and the radiation measuring device, wherein with the inclination state of the measuring surface of the radiation measurement apparatus relative to the surface of the object to be measured prompt the inclination correcting to be zero
Whether the measurement surface of the radiation measuring instrument is within the optimal measurement distance range
A distance display unit that displays whether contamination degree conversion for converting the radiation contamination as measured from a given distance with respect to the object to be measured based on the measurement results measured in the previous SL radiation counter to the distance detected by said distance detector And a unit .

[0010]

According to the above construction, the radiation meter measures the radiation emitted from the radioactive substance attached to the surface of the object to be measured, and the distance detector detects the distance between the object to be measured and the radiation meter. At this time, the interval display unit prompts the inclination correction so that the inclination state of the measurement surface of the radiation measuring instrument with respect to the surface of the object to be measured becomes zero, so that the surface of the object to be measured and the measurement surface are parallel. I do. As a result, the measurement conditions are stabilized. Then, the contamination degree conversion unit converts the measured value measured by the radiation meter into a radiation contamination degree measured from a predetermined distance with respect to the measured object based on the distance detected by the distance detector. Therefore, even when the distance between the radiation measuring instrument and the object to be measured changes, it is possible to measure the radiation with a constant detection efficiency and measure the degree of contamination.
Further, since it is displayed whether or not the measurement surface of the radiation measuring instrument is within the optimum measurement distance range, the measurement is further stabilized .

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1A is a schematic external view of a portable radioactive surface contamination detector (hereinafter referred to as a survey meter) 10. In this survey meter 10, a measurer holds the main body 12 by hand, and causes a radiation measuring instrument (hereinafter referred to as a probe) 14 having a radiation detecting surface 14a to face a measuring surface of an object to be measured (not shown). Probe 14 along
, And sequentially measure the radiation to calculate the degree of radiation contamination.

This embodiment is characterized in that the distance from the radiation detection surface 14a of the probe 14 to the measurement surface of the object to be measured is detected, and the measured value of the radiation detected by the probe 14 is converted based on the distance. Then, the measured value is to be displayed as a degree of radiation contamination measured from a predetermined distance with respect to the measured object.

As shown in FIG. 1A, the survey meter 10 includes a probe 14 having an exposed radiation detection surface 14a connected to a main body 12 via a cable 13.
The probe 14 includes a GM tube, a plastic scintillator, and the like, and measures radiation emitted from a radioactive substance attached to the surface of the detection target. A data display unit 16 for displaying the degree of radiation contamination and various data is provided on a surface of the main unit 12, a power switch of a survey meter,
In addition to the speaker 20 that emits an alarm sound or the like based on the data displayed on the data display unit 16, a power switch of a survey meter (not shown)
An alarm stop switch or the like for stopping the operation of “0” is arranged.

As shown in FIG. 1B, a semiconductor position detecting element and a distance detector 24a of a distance detector using infrared rays and ultrasonic waves are arranged near the radiation detecting surface 14a of the probe 14. I have.

The survey meter 1 configured as described above
0 will be described with reference to the configuration block diagrams of FIGS.

The person who measures the degree of radiation contamination is the survey meter 10.
And the power switch is turned ON. Then, in order to eliminate the influence of radiation (background) originally present in the natural world or an object other than the object to be measured, the background is measured by the probe 14 according to a predetermined procedure as a preliminary measurement, and the contamination degree conversion unit 26 described later is used. The measured background value is stored in the memory 30 connected to the internal CPU 28. After the measurement of the background, the probe 14 is brought close to the measurement surface of the object to be measured for the main measurement of the object, scanned along the measurement surface, sequentially measures the radiation, and stores the measured values in the memory 3.
Store to 0. At the same time, the distance detector 24
The distance between the radiation detection surface 14a and the object to be measured is measured, and the measured distances are sequentially stored in the memory 30.

Based on the input data, the pollution degree conversion unit 26 performs an operation such as converting a measured value of radiation into a radiation pollution degree measured from a predetermined distance to an object to be measured, and controls the survey meter 10 as a whole. CPU 28 to perform
And a memory 30 for storing various data.
The memory 30 temporarily stores the measured data, and previously stores the reference detection efficiency, the allowable contamination degree, and the like when measuring the measurement object in the same contamination state by changing the measurement distance.

The CPU 28 converts the measured value of the radiation measured by the probe 14 based on the distance measured by the distance detector 24 in order to convert the measured value of the radiation from a fixed distance to the degree of contamination of the radiation when the surface to be measured is measured. I do. In performing the conversion of the degree of contamination, using a background value stored in the memory 30 and a previously stored reference detection efficiency and the like, a value obtained by making the detection efficiency of the true radiation contamination state of the measured object constant, That is, the detection efficiency is made constant by converting the measured contamination level when the measurement target surface is measured from a certain distance.

Then, the measured pollution degree converted by the pollution degree conversion section 26 is displayed on the data display section 16. At the same time, the CPU 28 compares the measured contamination degree with the allowable contamination degree. If the measured contamination degree exceeds the allowable contamination degree, an alarm sound is emitted from the speaker 20 to alert the measurer. The data display unit 16 may display data such as the distance to the measured object and the measured value of radiation in addition to the degree of contamination.

In this embodiment, the distance detecting section 24a of the distance detector 24 is connected to the radiation detecting surface 1 as shown in FIG.
4a has been described only on one side, but when detecting radiation, the measurement surface of the object to be measured and the radiation detection surface 14
a is desirably parallel. Therefore, a plurality of distance detection units 24a may be provided in the vicinity of the radiation detection surface 14a, for example, in four directions at 90 ° intervals, and the inclination state of the probe 14 may be added to the conversion data for the measured contamination degree.

Further, in order to allow the measurer to easily recognize the inclination state of the probe 14 and the optimum distance to the object to be measured,
An interval display section 32 composed of LEDs and the like as shown in FIG.
May be provided in the main body 12 of the survey meter 10. The interval display unit 32 prompts a correction so that the inclination state of the probe 14 becomes zero by blinking four arrow display LEDs 32a facing the center, for example, and the center LED 32b
An indication of whether or not the probe 14 is within the optimal measurement distance range, for example, by illuminating red if the probe is too close or too far, and illuminating green when within the optimal measurement distance, Can be prevented from detecting extremely different measurement values.

[0023]

[0024]

As described above, according to the radioactive surface contamination detector of the present invention, the measured value of the radiation measured by the probe in accordance with the distance from the probe measured by the distance detector to the object to be measured. Can be converted into the degree of radiation contamination measured from a predetermined distance with respect to the measured object. Therefore, even when the distance between the probe and the object to be measured fluctuates, the degree of contamination can be measured by measuring radiation at a constant detection efficiency, and the surface of the object to be measured has irregular irregularities. Measurement can be performed with a constant detection efficiency even in the case where the measurement person changes.

Further, the measured contamination degree and the allowable contamination degree can be directly and accurately compared, and the radiation contamination degree of the measured object can be correctly recognized.

[Brief description of the drawings]

FIG. 1 is an explanatory view for explaining a radioactive surface contamination detector according to the present invention, wherein (a) is a schematic external view of the radioactive surface contamination detector, and (b) is a plan view of a radiation detection surface.

FIG. 2 is a configuration block diagram of a radioactive surface contamination detector according to the present invention.

FIG. 3 is a display example showing a tilt state and an approach state of a detection surface of the radioactive surface contamination detector according to the present invention.

[Explanation of symbols]

 14 Probe (radiation measuring device) 16 Data display unit 24 Distance detection unit 26 Pollution degree conversion unit 28 CPU 30 Memory

Continuation of the front page (56) References JP-A-3-92788 (JP, A) JP-A-6-273353 (JP, A) JP-A-59-54985 (JP, A) JP-A-60-227186 (JP, A) JP-A-62-297775 (JP, A) JP-A-62-285008 (JP, A) JP-A-5-312957 (JP, A) JP-A-5-302980 (JP, A) 5-2155861 (JP, A) JP-A-63-70186 (JP, A) JP-A-63-231287 (JP, A) JP-A-1-296183 (JP, A) JP-A-1-260389 (JP, A) A) JP-A-63-151884 (JP, A) JP-A-64-88283 (JP, A) JP-A-58-35483 (JP, A) Japanese Utility Model Showa 62-193505 (JP, U) (58) Survey Field (Int.Cl. ⁷ , DB name) G01T 1/169

Claims (1)

(57) [Claims] 1. A radiation measuring device for measuring radiation emitted from a radioactive substance attached to a surface of an object to be measured, and a distance detector for detecting a distance between the object to be measured and the radiation measuring device.
When the front with the inclination state of the measuring surface of the radiation measurement apparatus relative to the surface of the object to be measured prompt the inclination correcting to be zero
Whether the measurement surface of the radiation measuring instrument is within the optimal measurement distance range
Pollution degree be converted into radiation contamination as measured from a given distance with respect to distance display section and, the object to be measured based on the measurement results measured in the previous SL radiation counter to the distance detected by said distance detector that displays whether A portable radioactive surface contamination detector, comprising: a conversion unit;