JP2725978B2 - Scintillation 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 scintillation detector in which a plurality of detection units including a scintillator are connected.

[0002]

2. Description of the Related Art In a nuclear power plant or the like, a large-area scintillation detector is used to inspect radioactive surface contamination of used clothes and tools. FIG. 4 shows an example of a conventional large-area scintillation detector. This scintillation detector is roughly divided into a detection unit 10 and a detection unit 12.
And the two detection units are coupled.

[0003] The two detection units 10 and 12 are:
Each has the same structure, and one of them will be described below as a representative.

In FIG. 4, a scintillator plate 20 is disposed on the inner bottom surface of the shield case 14. The bottom wall forming the sensitive surface of the shield case 14 is made of, for example, an aluminum foil 18 that transmits radiation. Two photomultiplier tubes 16 are provided on the upper part of the shield case 14.
When light emission is detected simultaneously by the two photomultiplier tubes 16, counting is performed in a measuring unit (not shown).

[0005] When detecting radioactivity adhering to clothing or the like using such a scintillation detector, a belt conveyor device (not shown) is provided below the scintillation detector, and the clothing is attached to the belt conveyor device. The measurement is performed in a state where it is carried and transported. In the example shown in FIG. 4, for example, an object to be measured is conveyed from the front side to the back side of the paper surface of FIG.

[0006]

However, in the conventional scintillation detector shown in FIG. 4, since the two detection units 10 and 12 are connected, there is a problem that a dead zone 100 is generated at the connection portion. That is, even if there is a radioactive substance under the region where the two detection units are connected, there is a problem that it cannot be detected.

Therefore, in order to solve such a problem, for example, it is possible to make the size of the shield case 14 double and make the scintillator plate twice the size. However, since the detection unit does not function independently, there is a problem that the approximate position of the radioactive substance cannot be specified and the background increases.

An object of the present invention is to provide a scintillation detector in which a dead zone is eliminated while maintaining a unique measurement area of each detection unit to some extent.

[0009]

In order to achieve the above object, the present invention provides a shield case having a hollow interior, a partition plate for separating the inside of the shield case into a plurality of detection units, wherein comprises a scintillator plate provided with continuous close while mutually Oite the shield case inner bottom surface <br/> of, and a photomultiplier tube provided in an upper portion of the shield case for each of the detection units, wherein A lower portion of the partition plate is cut off to form an adjustment optical path for communicating the detection units with each other.

[0010]

According to the above construction, the detection unit is partitioned by the partition plate, but the lower part of the partition plate is cut off to form an adjustment optical path. Part of the light emission can be detected, and as a result, the dead zone can be eliminated while mutually covering the area to which the detection unit is connected.

In this case, when the radioactive substance is present at a position shifted from the center to one side, the measured value of one of the detecting units becomes large, and the measured values of both of the detecting units are substantially the same. In this case, it can be determined that the radioactive substance is located at the central position or spread uniformly to both.

[0012]

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

FIG. 1 shows the structure of a scintillation detector according to the present invention. This scintillation detector comprises a detection unit 10 and a detection unit 1 as in the prior art.
2 is comprised. Note that the same components as those of the conventional configuration shown in FIG. 4 are denoted by the same reference numerals, and description thereof will be omitted.

In the scintillation detector of the present embodiment, the shield cases of the respective detection units are connected, and a large shield case 30 is formed as shown in FIG. On the inner bottom surface of the shield case 30, the scintillator plates 20 are close to each other for each detection unit as in the conventional case.
It is provided continuously while touching . Note that the scintillator plates 20 are optically separated at their tangent sides. That is, the wraparound of light via the scintillator is prevented.

The bottom wall of the shield case 30 is made of aluminum foil 34 as in the conventional case.

In the scintillation detector of this embodiment,
As shown in FIG. 1, a partition plate 32 for separating the inside of the shield case 30 into two detection units is provided.

FIG. 2 is an enlarged view of the partition plate 32. As shown in the figure, the upper part of the partition plate 32 is fixed to the ceiling wall of the shield case 30, and the lower part of the partition plate 32 is cut off to communicate the space in each detection unit. That is, the adjustment optical path 40 is formed. The cut amount H is set, for example, to about one tenth of the height from the upper surface of the scintillator plate 20 to the ceiling of the shield case 30, for example.

As described above, by providing the adjustment optical path 40, for example, a part of the light emission generated in the vicinity of the detection unit 10 in the detection unit 12 is detected by the detection unit 10, and the measurement of each detection unit is performed. The regions will overlap each other in the middle.

FIG. 3 shows the sensitivity of each detection unit. In the figure, 200 is the sensitivity of the detection unit 10 and 202 is the sensitivity of the detection unit 12. As shown, both sensitivities complement each other in a portion corresponding to the conventional dead zone 100. As a result, a substantially uniform sensitivity can be formed from the right end to the left end. Note that the scintillator plates in the two detection units are not separated from each other,
The sensitivities in the case of a single sheet are indicated by 300 and 302, and it is understood that light wraparound occurs.

As described above, according to the scintillation detector of this embodiment, it is possible to eliminate the conventional dead zone and maintain a sensitivity equal to or higher than a predetermined value in all ranges. In addition, since the mutual detection units are not completely communicated with each other but provided with a fixed partition plate,
A sensitivity distribution can be generated in each detection unit, and as a result, the position of the radioactive substance can be specified to some extent.

In the embodiment described above, the partition plate 3
Although 2 is a flat plate, for example, it is preferable that the cross section is an inverted triangle.

[0022]

As described above, according to the present invention,
The dead zone can be eliminated while maintaining the measurement area of each detection unit to some extent.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a scintillation detector according to the present invention.

FIG. 2 is an enlarged view of a partition plate 32.

FIG. 3 is an explanatory diagram showing a sensitivity distribution of each detection unit.

FIG. 4 is a sectional view showing a conventional scintillation detector.

[Explanation of symbols]

 10, 12 detection unit 16 photomultiplier tube 20 scintillator plate 30 shield case 32 partition plate

Claims (1)

(57) [Claims] A shield case having a hollow interior; a partition plate for separating the inside of the shield case into a plurality of detection units;
A scintillator plate provided in series with each other in close proximity to each other, and, for each of the detection units, a photomultiplier tube provided on an upper portion of the shield case. An scintillation detector, wherein an adjustment optical path for communicating the detection units is formed.