JP2005214869A - Equivalent dose type radiation detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem wherein a perforated filter or the like is provided to satisfy a specification by one detector since efficiency for energy is specified in an equivalent dose type radiation detector, wherein a material of the perforated filter, a numerical aperture of a hole therein and the like are required to be optimized and regulation therefor is troublesome, and wherein measuring precision is low because one portion of a radiation is shielded by the perforated filter. <P>SOLUTION: This semiconductor radiation detector is constituted of plurality of layers of semiconductor radiation detectors 2a-2c, and detects the radiation of low energy by the first layer of the radiation detector 2a, the radiation of middle energy by the second layer of the radiation detector 2b, and the radiation of high energy by the third of the radiation detector 2c, respective radiation detection signals are multiplied with weighting factors by multiplying factor multiplexing parts 31, 32, 33, and values therein are summed up to obtain a proper energy characteristic. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an equivalent dose type radiation detector that monitors the radiation dose in the surrounding environment of a nuclear facility from the viewpoint of radiation protection.

  In a nuclear power plant such as a nuclear power plant, during normal operation, the radiation exposure exceeding the dose target value stipulated in the basic guidelines for safety design is considered from the viewpoint of radiation protection for the general public and employees of the power plant. Must not be given.

  The release of radioactive materials contained in gaseous and liquid waste from nuclear power plants to the environment must not exceed the amount specified for one year as the allowable exposure dose outside the power station's surrounding monitoring area. Don't be.

Furthermore, based on the guidelines, radiation protection is aimed at by determining the target effort for the exposure dose to the general public.
As one of methods for evaluating these exposure doses, an equivalent dose type radiation detector has been conventionally used.

  FIG. 5 is a diagram schematically showing a conventional equivalent dose radiation detector, wherein 1 is radiation such as X-rays and γ-rays, 2 is a semiconductor radiation detector provided facing the incident direction of the radiation 1, 3 is a signal amplifier.

  In such a conventional equivalent dose type radiation detector, the radiation 1 incident on the semiconductor radiation detector 2 from the ambient environment is detected as the radiation detection signal S by the semiconductor radiation detector 2 and an electric signal corresponding to the radiation dose. 4 is input to the signal amplifier 3.

  The dose equivalent of the surrounding environment is monitored from the radiation detection signal amplified by the signal amplifier 3, and if the dose equivalent exceeds the effort target value, an alarm is issued to protect the radiation.

  However, in the conventional equivalent dose type radiation detector, the efficiency with respect to the energy of the semiconductor radiation detector 2 is defined. Therefore, in order to satisfy the specification with one semiconductor radiation detector, the semiconductor radiation detector 2 is used. It is suitable by providing a perforated filter 5 on the front surface of the substrate and allowing the radiation 1 to enter the semiconductor radiation detector 2 through the perforated filter 5 and optimizing the material of the perforated filter 5, the aperture ratio of the holes, etc. It was necessary to obtain good energy characteristics.

  However, in order to optimize the material of the perforated filter 5, the aperture ratio of the holes, etc., it is necessary to make troublesome adjustments, so it is difficult to easily set the energy sensitivity characteristics of the semiconductor radiation detector 2. .

  Further, when the perforated filter 5 is provided on the front surface of the semiconductor radiation detector 2, the incidence of radiation is partially blocked by the perforated filter 5, and the measurement accuracy is lowered due to blocking of the detection signal.

  The present invention has been made to solve the above problems, and an object thereof is to obtain an equivalent dose type radiation detector that can easily set the energy sensitivity characteristic of a semiconductor radiation detector and has improved measurement accuracy. To do.

  In order to achieve the above object, the invention according to claim 1 is provided with a plurality of layers provided opposite to the incident direction of radiation and absorbing radiation in different energy regions and outputting a radiation detection signal corresponding to the radiation dose. The semiconductor radiation detectors of the above, the radiation detection signals from the semiconductor radiation detectors of the respective layers are inputted as electric signals, amplified, and the radiation detection signals amplified by the signal amplifiers are multiplied by the weight, And a signal calculation unit for adding calculation results.

  According to the equivalent dose type radiation detector of the present invention, the energy sensitivity characteristic of the semiconductor radiation detector can be easily set, and the measurement accuracy can be improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description of the embodiment, the same parts as those in the conventional equivalent dose type radiation detector shown in FIG.

  FIG. 1 is a diagram showing a first embodiment of the present invention. In FIG. 1, 1 is radiation such as X-rays and γ-rays, 2a, 2b and 2c are provided opposite to the incident direction of the radiation 1. FIG. The first layer semiconductor radiation detector 2a, which is arranged next to each other, for example, three layers of semiconductor radiation detectors, which is disposed closest to the radiation 1 incident side, absorbs radiation having a relatively low energy, and the second layer The semiconductor radiation detector 2b absorbs radiation with energy up to an intermediate region, and the semiconductor radiation detector 2c of the third layer is set so as to absorb radiation up to high energy such as X-rays and γ-rays. . 3 is a signal amplifier, and 6 is a signal calculation unit.

According to the equivalent dose type radiation detector according to the first embodiment of the present invention, the radiation 1 incident on the semiconductor radiation detector 2 from the surrounding environment has a relatively low energy region of the first layer. It is absorbed by the semiconductor radiation detector 2a and detected as a radiation detection signal S1.
Similarly, the radiation in the intermediate energy region is absorbed by the semiconductor radiation detectors 2a and 2b in the first layer and the second layer, and is detected as a radiation detection signal S2.

Furthermore, radiation in a high energy region such as X-rays and γ-rays is absorbed by the semiconductor radiation detectors 2a, 2b, and 2c of the first layer, the second layer, and the third layer, and is detected as a radiation detection signal S3.
The radiation detection signals S <b> 1 to S <b> 3 detected by the semiconductor radiation detectors 2 a, 2 b, and 2 c of each layer are converted into electrical signals 4 corresponding to the radiation doses, output, and sent to the signal amplifier 3.

The radiation detection signals S <b> 1 to S <b> 3 input as the electric signal 4 are amplified by the signal amplifier 3 and sent to the signal calculation unit 6.
In the signal calculation unit 6, as shown in FIG. 2, the radiation detection signals S <b> 1 to S <b> 3 are multiplied by multiplication factors 21, 22, and 23 in the weight multiplication units 31, 32, and 33, and the calculation results are added in the addition calculation unit 7. to add.

For example, when the energy sensitivity is low, it is absorbed by the semiconductor radiation detector 2a of the first layer, and the detected radiation detection signal S1 is multiplied by a higher weight factor 21.
Energy sensitivity is obtained by multiplying the radiation detection signals S1 to S3 detected by the semiconductor radiation detectors 2a, 2b, and 2c of each layer in this way by the weights 21 to 23 and adding the values to obtain the detection output 8. The characteristics are corrected, the dose equivalent of the surrounding environment is monitored from the added radiation detection output 8, and if the effort target value is exceeded, an alarm is issued to protect the radiation.

According to the present embodiment, energy is obtained by multiplying the radiation detection signals S1 to S3 detected by the semiconductor radiation detectors 2a, 2b, and 2c of each layer by the weights 21 to 23 and adjusting the added weight of each layer. Sensitivity characteristics can be set easily.
Further, since a perforated filter is not used as in the prior art, there is no blockage of radiation incidence, and a large amount of detection signal can be obtained, thereby improving measurement accuracy.

  Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 3 is a block diagram showing a signal calculation unit according to the second embodiment of the present invention. In FIG. 3, 9 is a signal ratio for inputting the radiation detection signals S1 to S3 and calculating the output ratio of the radiation detection signals. The calculation unit 10 is a nuclide estimation calculation unit that measures the ratio of the radiation detection signal to the measurement nuclide in advance and stores the table.

  In the case of such an equivalent dose type radiation detector, the radiation detection signals S1 to S3 detected by the semiconductor radiation detectors 2a, 2b and 2c are sent to the signal comparison calculation unit 9, where each radiation detection signal S1 to S1 is detected. The ratio of the output of S3 (eg, S2 / S1, S3 / S1, S3 / S2) is calculated.

The value of the calculated ratio is sent to the nuclide estimation calculation unit 10, where it is compared with the ratio of the measured nuclide stored in the table, and if the ratio matches, the nuclide is identified and displayed. Alternatively, it is output to a host computer.
According to the present embodiment, the measurement target nuclide can be estimated, and the cause of the exposure can be easily estimated.

Next, a third embodiment of the present invention will be described with reference to the drawings.
In FIG. 4, 2a to 2c are three-layer semiconductor radiation detectors arranged side by side, and the first-layer semiconductor radiation detector 2a arranged closest to the radiation 1 incident side is a color CCD detector. The color sensor 11 has a function of discriminating colors.

  Reference numeral 12 denotes a scintillator disposed on the front surface of the color sensor 11. A scintillator sensitive to α rays (for example, ZnS) is provided on the front surface, and a scintillator sensitive to β rays and γ rays on the rear surface (for example, a plastic scintillator). ).

  According to this embodiment, since the emission color of the scintillator 12 differs depending on the type of radiation 1 incident on the semiconductor radiation detector, the line type of the radiation 1 can be easily identified by detecting the emission color with the color sensor 11. can do.

The block diagram which shows schematic structure of the equivalent dose type radiation detector by the 1st Embodiment of this invention. The block diagram which shows the structure of the signal calculating part in the 1st Embodiment of this invention. The block diagram which shows the structure of the signal calculating part of the equivalent dose type radiation detector by the 2nd Embodiment of this invention. The block diagram which shows schematic structure of the equivalent dose type | mold radiation detector by the 3rd Embodiment of this invention. The block diagram which shows schematic structure of the conventional equivalent dose type radiation detector.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Radiation, 2, 2a, 2b, 2c ... Semiconductor radiation detector, 3 ... Signal amplifier, 4 ... Electric signal, 5 ... Perforated filter, 6 ... Signal calculating part, 7 ... Addition calculating part, 8 ... Detection output, DESCRIPTION OF SYMBOLS 9 ... Signal comparison calculating part, 10 ... Nuclide estimation calculating part, 11 ... Color sensor, 12 ... Scintillator 21, 22, 23 ... Weight factor, 31, 32, 33 ... Weight factor multiplication part, S1, S2, S3 ... Radiation Detection signal.

Claims (3)

  A plurality of layers of semiconductor radiation detectors provided opposite to the direction of incidence of radiation and absorbing radiation in different energy regions and outputting radiation detection signals according to the radiation dose; and from the semiconductor radiation detectors of the respective layers A signal amplifier for inputting and amplifying a radiation detection signal as an electric signal, and a signal calculation unit for multiplying each radiation detection signal amplified by the signal amplifier by a weight and adding the calculation result. Equivalent dose type radiation detector.   A signal ratio calculation unit that calculates the ratio of the radiation detection signal output from the semiconductor radiation detector of each layer, and a nuclide estimation that identifies the radionuclide from the ratio of the radiation detection signal output calculated by the signal ratio calculation unit The equivalent dose type radiation detector according to claim 1, further comprising a calculation unit. The semiconductor radiation detector arranged on the most radiation incident side of the multi-layer semiconductor radiation detector is constituted by a color sensor, and the front surface on the radiation incidence side of the color sensor is sensitive to different types of radiation. 2. The equivalent dose radiation detector according to claim 1, further comprising a scintillator.

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