JPH0541422Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a radioactive contamination measuring device, and particularly to a device for measuring weak radioactivity on the surface of a sealed bag.

[Problems with the prior art] In Japan, radioisotopes and radiation generating devices are only allowed to be handled in radioisotope handling facilities that meet the conditions stipulated by law, and areas where radiation and radioactive substances are handled are not allowed to be handled by the general public. A controlled area has been established to physically isolate the area from the surrounding environment, manage human exposure to radiation, and restrict access.

Furthermore, in order to prevent the spread of radioactive contamination, surface contamination inspections are required for materials exported from controlled areas to ensure that the surface contamination surface density is below the control standard value. Among these, alpha rays have a short range and cause local disturbances, so management standards are particularly strict and set at a low areal density.

FIG. 1 shows a schematic configuration of a conventional radioactive contamination measuring device, in which an α-ray detector 12 is arranged facing a sealed bag 10 containing waste, and
In FIG. 1, α-rays are detected, and the measurement unit 1 connected to the α-ray detector 12
At step 4, the alpha ray concentration is displayed.

The airtight bag 10 is a carton box for waste that is sealed in a plastic bag, and when it is transported out of a controlled area, it must be confirmed that the density of surface contamination is below the control standard value.

In order to measure the surface contamination of the sealed bag 10 using the conventional radioactive contamination measuring device as shown in FIG. 1, first, the detection surface of the α-ray detector 12 is brought as close as possible to the sealed bag 10 so that α-rays can be easily detected.
Read the displayed value.

Next, the detection area of the α-ray detector 12 is
Since the surface area of the sealed bag 10 is extremely small compared to the surface area of Confirm that the following is true.

However, it is very difficult to reliably measure the weak radioactivity of a surface having an uneven shape like the sealed bag 10 using the conventional radioactive contamination measuring device as shown in FIG.

That is, since the range of alpha rays in the air is very short, several centimeters, it is not easy to detect alpha rays from the convex surface of the airtight bag 10 whose surface has an uneven shape as shown in FIG. However, with a concave surface, the distance from the detection surface of the α-ray detector 12 becomes long, so it is very difficult to reliably detect weak radioactivity.

Furthermore, in the conventional device shown in FIG. There is a problem in that it is necessary to bring the surfaces as close as possible, move the α-ray detector 12, and measure the entire surface while reading the display on the measuring section 14, which requires a great deal of labor and time.

Purpose of the invention The present invention was made in view of the above-mentioned conventional problems, and its purpose is to provide a radioactive contamination measuring device that can measure the entire weak radioactivity from the surface of a sealed bag at once with high sensitivity. be.

[Means and effects for solving the problems] In order to achieve the above object, the present invention provides a reduced pressure container having a measurement chamber inside which seals an airtight bag for storing materials carried out from a radiation controlled area; It includes a detector consisting of a scintillator plate installed on the peripheral wall of the room and a photomultiplier tube connected to the scintillator plate. The method is characterized in that radioactive contamination on the surface of the sealed bag is measured by bringing the surface sufficiently close to the detector.

[Example] FIG. 2 shows a radioactive contamination measuring device according to the present invention, which includes a vacuum container 22 in which the pressure in a measurement chamber 24 is reduced by a pressure reduction device 20, and a measurement chamber 4.
It consists of a detector 26 consisting of a scintillator plate installed on the inner peripheral wall and a photomultiplier tube connected to the scintillator plate, and a measurement unit 28 that processes electrical signals from the detector 26. .

The unique feature of this invention is that by reducing the pressure inside the vacuum container, the airtight bag is inflated and the surface of the airtight bag is brought close enough to the detector, allowing radioactive contamination on the surface to be measured at once with high sensitivity. It is.

That is, according to the present invention, the airtight bag 10 as shown in FIG.
The vacuum container 22 is sealed by the vacuum device 20.
When the pressure inside the measurement chamber 24 is reduced, a difference between the internal pressure and the internal pressure of the airtight bag 10 is generated, causing the airtight bag 10 to expand, as shown in FIG.
0 and the detection surface of the detector 26 are brought into close contact.

Therefore, in such a state of high detection sensitivity, the α rays on the surface of the sealed bag 10 are reliably detected at once by the detector 26 and sent as a signal to the measuring section 28.

As explained above, surface contamination can move and spread, and there is also a risk that it may become a source of contamination on hands, etc., and be ingested, so it is important to avoid removing waste from controlled areas. Control standards for surface contamination are strictly defined, but according to the present invention, it is possible to reliably measure weak spots and radioactivity on the surface of an airtight bag having an uneven shape with high sensitivity.

[Effects of the invention] As described above, according to the invention, it is possible to reliably measure the weak radioactivity on the surface of a sealed bag with high sensitivity and in a short time, thereby reducing radioactive contamination. It has a great effect on prevention.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a conventional radioactive contamination measuring device, and FIG. 2 is an explanatory diagram showing a radioactive contamination measuring device according to the present invention. 10... airtight bag, 20... pressure reducing device, 22...
Decompression container, 24...Measurement chamber, 26...Detector, 2
8...Measurement section.

Claims (1)

[Scope of utility model registration request] A depressurized container having a measurement chamber in which a sealed bag containing items carried out from the radiation control area is housed, a scintillator plate installed on the peripheral wall of the measurement chamber, and a photomultiplier tube connected to the scintillator plate. A detector consisting of a detector, characterized in that by reducing the pressure inside the vacuum container, the airtight bag is inflated to bring the surface of the airtight bag sufficiently close to the detector, and radioactive contamination on the surface of the airtight bag is measured. Radioactive contamination measuring device.