JP7108530B2 - Shield inspection method - Google Patents

Description

The present invention relates to a method of inspecting a shield.

When storing, transporting, or handling radioactive materials, the concentration of radiation emitted from the radioactive materials is measured in order to reduce the exposure of workers. For example, Patent Literature 1 discloses a configuration for detecting a radiation dose (dose) with a germanium detector.

Such radioactive substances are housed in a housing space defined by a shield having a predetermined radiation shielding performance. In order to suppress leakage of radiation to the outside of the accommodation space, it is necessary to inspect whether or not the shield has a predetermined radiation shielding performance.

To inspect a shield, a source of radiation is placed on a first side of the shield and a detector is placed on a second side of the shield. A detector, on a second side of the shield, detects the dose of radiation emitted from the source and passed through the shield. The radiation attenuation rate by the shield is obtained from the dose emitted from the radiation source and the dose detected by the detector. Whether or not the shield has a predetermined radiation shielding performance can be determined based on this attenuation factor.

JP-A-9-230051

When inspecting the shield as described above, if the radiation source and the detector are shifted in the direction along the surface of the shield between the first side and the second side of the shield, attenuation rate detection accuracy is reduced. For this reason, it is necessary to accurately face the radiation source and the detector on the first side and the second side with the shield interposed therebetween. Inspection of the shield is performed over the entire surface of the shield. Therefore, the inspection positions of the shield are set at a number of positions spaced along the surface of the shield. At each of these many inspection positions, it takes time and effort to precisely align the radiation source and the detector across the shield. In addition, if the surface of the shield is not flat, but has unevenness or is connected to another wall, the radiation source and the detector may It may be difficult to accurately determine the position of
SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for inspecting a shield that can efficiently inspect the shield.

In order to solve the above problems, the present invention employs the following means.
According to the first aspect of the present invention, a shield inspection method is a shield inspection method for shielding radiation, comprising a correlation data acquiring step, a dose reference value acquiring step, a passing dose detecting step, an attenuation A rate acquisition process and a determination process are provided. The correlation data acquisition step acquires dose-distance correlation data indicating a correlation between a distance from a radiation source and a dose of radiation emitted from the radiation source. In the dose reference value acquisition step, when radiation is emitted from the radiation source spaced from the installation position of the shield to be installed to the first side of the installation position, it is set to the second side of the installation position. A reference dose value is obtained at each of a plurality of examination positions having different distances from the radiation source . Acquisition of the dose reference value at each of the plurality of examination positions is performed based on the distance between the radiation source and each of the examination positions and the dose distance correlation data. In the passing dose detection step, the radiation source is arranged on the first side of the shield installed at the installation position, and the detector is arranged on the second side of the shield. In the passing dose detection step, at each of the plurality of inspection positions on the second side of the shielding body, the passing dose of the radiation emitted from the radiation source in a fixed state passing through the shielding body is detected by the detector. do. In the attenuation rate obtaining step, at each of the examination positions where the passing dose is detected in the passing dose detecting step, the dose reference value obtained in the dose reference value obtaining step and the passing dose Attenuation rate of radiation by the shield is obtained based on the dose. The determination step determines whether or not the attenuation rate is equal to or less than a predetermined threshold.

With this configuration, in the dose reference value acquisition step, when radiation is emitted from the radiation source, the dose at a plurality of inspection positions set on the second side of the installation position of the shield is calculated as the radiation source. Acquired based on the distance to each examination position and the dose-distance correlation data. By obtaining in advance the correlation between the distance from the radiation source and the dose as dose-distance correlation data, it is possible to obtain the dose-distance correlation data at each of a plurality of examination positions with different distances from the radiation source without shields installed. can give a baseline dose of Therefore, it is possible to reduce the trouble of radiating radiation from the radiation source to a plurality of inspection positions before installing the shield and measuring the dose without installing the shield.
In the passing dose detection step, the passing dose of radiation emitted from the radiation source is detected at the inspection position on the second side of the shield. Here, in the dose reference value acquisition step, the dose reference values are acquired at a plurality of examination positions having mutually different distances from the radiation source. Therefore, in the passing dose detection step, even if the distances between the detector and the radiation source are different at a plurality of inspection positions, the attenuation rate can be obtained in the attenuation rate obtaining step. As a result, it is not necessary to move both the detector and the radiation source to the inspection position when detecting the dose at each inspection position. Just do it. Therefore, the need to move the radiation source according to the inspection position and accurately adjust the positional relationship with the detector can be suppressed. As a result, it is possible to efficiently inspect the shield.

According to the second aspect of the present invention, the passing dose detection step according to the first aspect may detect passing doses at a plurality of examination positions while the radiation source is fixed.
By configuring in this way, the radiation source is moved according to the inspection position by detecting the passing dose at a plurality of inspection positions while the radiation source is fixed, and the positional relationship with the detector is accurately adjusted. reduce the need to As a result, it is possible to efficiently inspect the shield.

According to the third aspect of the present invention, the correlation data acquisition step according to the first or second aspect calculates the dose when radiation is emitted from the radiation source at the first position of the shield to be installed at the installation position. Detecting at multiple positions along a virtual plane corresponding to two surfaces or at multiple positions linearly varying distances from the radiation source. The correlation data acquisition step includes, based on the detected dose value at each of the plurality of positions and the correlation of the distance between each of the positions and the radiation source, other distances different from the plurality of positions. The dose-distance correlation data is obtained by calculating the dose at the position.
By configuring in this way, if the dose is detected at a plurality of positions along the virtual plane, the dose is detected at a plurality of positions at different distances from the radiation source. Also, if the dose is detected at a plurality of positions whose distances from the radiation source are linearly changed, the doses are detected at a plurality of positions whose distances from the radiation source are different from each other. Based on the detection result, it is possible to interpolate the dose at other positions different in distance from the plurality of positions where the radiation was actually emitted and the dose was detected. As a result, when obtaining the dose-distance correlation data, it is possible to reduce the number of positions where radiation is actually emitted and the dose is detected. This also makes it possible to efficiently inspect the shield.

According to the shield inspection method, the shield can be inspected efficiently.

FIG. 4 is a diagram showing an example of a space partitioned using a shield to be inspected by the shield inspection method according to the embodiment of the present invention; It is a figure which shows an example of the said shielding body, and is sectional drawing which shows a shielding body extended in a horizontal direction. FIG. 10 is a view showing another example of the shield, and is a cross-sectional view showing the shield extending in the vertical direction; 4 is a flow chart of a shield inspection method according to the first embodiment of the present invention; It is a figure which shows the arrangement|positioning of a radiation source and a detector in the correlation data acquisition process of the said shielding inspection method. FIG. 4 is a plan view showing how doses are detected at a plurality of positions in the correlation data acquisition step; It is a graph which shows an example of the dose distance correlation data acquired by the said correlation data acquisition process. It is a figure which shows the arrangement|positioning of a radiation source and a detector in the correlation data acquisition process of the said shielding inspection method. FIG. 10 is a diagram showing a method of detecting at a plurality of positions where the distance from the radiation source is linearly changed in the correlation data acquisition step of the modified example of the shield inspection method.

A method for inspecting a shield according to an embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing an example of a space partitioned using a shield to be inspected by a shield inspection method according to an embodiment of the present invention. FIG. 2 is a diagram showing an example of the shield, and is a cross-sectional view showing the shield extending in the lateral direction. FIG. 3 is a diagram showing another example of the shield, and is a cross-sectional view showing the shield extending in the vertical direction.

As shown in FIG. 1, a space S in which radioactive materials are stored, transported, handled, etc. is partitioned by shields 20A and 20B.
As shown in FIGS. 1 and 2, the shield 20A is installed extending in the horizontal direction, and constitutes the floor, ceiling, etc. of the space S, for example. The shield 20A includes a steel plate 21 and a concrete layer 22 made of concrete laid on the steel plate 21 with a predetermined thickness.

As shown in FIGS. 1 and 3, the shield 20B is installed to extend in the vertical direction, and constitutes the wall of the space S, for example. The shield 20B includes a pair of two steel plates 23 spaced apart in the horizontal direction, and a concrete layer 24 placed and filled between the steel plates 23 .

Here, when the radiation to be shielded is gamma rays, the concrete layers 22 and 24 are used for the shields 20A and 20B as described above. When the radiation to be shielded is neutron rays, the shields 20A and 20B may be provided with paraffin layers 22P and 24P made of paraffin (including polyethylene) instead of the concrete layers 22 and 24. Moreover, even when the radiation to be shielded is neutron rays, the concrete layers 22 and 24 may be used for the shields 20A and 20B.

By partitioning the space S with such shields 20A and 20B (hereinafter, the shields 20A and 20B are simply referred to as the shields 20), leakage of radiation to the outside of the space S is suppressed.

Next, a method for inspecting the shield 20 as described above will be described.
FIG. 4 is a flow chart of the shield inspection method according to the first embodiment of the present invention. FIG. 5 is a diagram showing the arrangement of the radiation source and the detector in the correlation data acquisition step of the shield inspection method. FIG. 6 is a plan view showing how doses are detected at a plurality of positions in the correlation data acquisition step.
As shown in FIG. 4, the inspection method for the shield 20 according to the present embodiment includes a correlation data acquisition step S1, a dose reference value acquisition step S2, a shield installation step S3, a passing dose detection step S4, an attenuation It includes a rate acquisition step S5 and a determination step S6. In the inspection method of the shield 20, it is inspected whether the shield 20 has a predetermined radiation shielding performance.

As shown in FIGS. 5 and 6, the inspection method for the shield 20 uses a radiation source 101 and a detector 102 .
The radiation source 101 emits, for example, gamma rays as radiation for inspecting the shield 20 . The radiation source 101 includes a radiation source container 101a containing a radiation source, a transmission tube 101b, and a collimator 101c. As the radiation source housed in the radiation source container 101a, for example, when the target radiation is gamma rays, a radioactive isotope ⁶⁰ Co (cobalt 60) or the like can be used. When the target radiation is a neutron beam, a radioactive isotope ²⁵² Cf (Californium 252) or the like can be used as the radiation source.
In the radiation source 101, the radiation source accommodated in the radiation source container 101a is pushed out to the collimator 101c via the transmission tube 101b and moves. A radiation source moved to the collimator 101c emits radiation.

Detector 102 detects the dose of radiation. If the target radiation is gamma rays, the detector 102 may be, for example, an ionization chamber survey meter. When the target radiation is a neutron beam, the detector 102 can use, for example, a neutron survey meter.

In the correlation data obtaining step S1, dose-distance correlation data indicating the correlation between the distance from the radiation source 101 and the dose of radiation emitted from the radiation source 101 is obtained. The correlation data acquisition step S1 detects the dose of radiation emitted from the radiation source 101 at a plurality of positions without the shield 20 provided.

In the correlation data acquisition step S1, the radiation source 101 is arranged in a predetermined positional relationship. Specifically, the collimator 101c of the radiation source 101 is separated from the planned installation position (installation position) P of the shield 20 to be installed to the first side of the shield 20 (the right side of the paper surface in FIGS. 5 and 6). position R. Here, in order to indicate the position R where the collimator 101c is installed in preparation for the dose detection step S4 to be performed later, the floor surface or the like may be marked.
The detector 102 corresponds to the surface 20f on the second side of the shield 20 to be installed at the planned installation position P of the shield 20 (the side opposite to the first side with the shield 20 interposed therebetween). It is placed at a position along the virtual plane V where the

As shown in FIG. 6, after the radiation source 101 and the detector 102 are arranged in this manner, at each of a plurality of positions X along the virtual plane V, the radiation emitted from the collimator 101c of the radiation source 101 A dose D 0 is detected by the detector 102 . For this, the radiation source 101 is fixed at the position R, the detector 102 is moved to a plurality of positions X along the virtual plane V, and the dose D0 is detected at each position X.

Specifically, first, the detector 102 is placed at a position X1 directly facing the radiation source 101 (the position where the distance L from the radiation source 101 is the closest). In this state, the detector 102 detects the dose D0 of radiation emitted from the collimator 101c of the radiation source 101 .

Next, the detector 102 is moved along the virtual plane V in one direction (for example, vertical direction) from the position X1 directly facing the radiation source 101 to a position X2 separated by a predetermined dimension, for example, 100 to 200 mm. In this state, the detector 102 detects the dose D0 of radiation emitted from the collimator 101c of the radiation source 101 .

Thereafter, the position of the detector 102 is moved along the virtual plane V by a predetermined distance, and the dose of radiation emitted from the collimator 101c is detected at each position X, which is sequentially repeated.
In this way, the radiation dose D0 emitted from the collimator 101c of the radiation source 101 fixed at the position R is detected at a plurality of positions X by moving the detector 102 along the virtual plane V. FIG.

Here, the dose D0 may be detected at a plurality of positions X spaced apart on a straight line along the virtual plane V, for example. Of course, the dose D0 may be detected at a plurality of vertically spaced positions X within a plane along the virtual plane V, or may be performed at a plurality of vertically and horizontally spaced grid positions. It may be performed at a plurality of positions X in a shape.
The detection of the radiation dose D0 at the plurality of positions X may be performed at a location different from the installation location of the shield 20. is preferably carried out at

Next, in the correlation data acquisition step S1, based on the dose D0 detected at each of the plurality of positions X, the dose indicating the correlation between the distance L from the radiation source 101 and the dose D0 of the radiation emitted from the radiation source 101 Distance correlation data is acquired by calculation. For this, based on the correlation between the distance L from the collimator 101c of the radiation source 101 at each of the plurality of positions X and the dose D0 detected at the plurality of positions X, the distance L from the plurality of positions X is A dose at a different position (for example, a position between the position X1 and the position X2) is obtained by calculation using an appropriate interpolation formula.

FIG. 7 is a graph showing an example of dose-distance correlation data obtained in the correlation data obtaining step.
As shown in FIG. 7, in the dose distance correlation data K, the dose tends to decrease as the distance of the radiation source 101 from the collimator 101c increases.

FIG. 8 is a diagram showing the arrangement of the radiation source and the detector in the correlation data acquisition step of the shield inspection method.
In the dose reference value acquisition step S2, a dose reference value D1 is acquired at each of a plurality of inspection positions M where the passage dose D2 is detected in the passage dose detection step S4. As shown in FIG. 8, a plurality of inspection positions M are set at a plurality of positions along the virtual plane V. As shown in FIG. A plurality of inspection positions M are set (planned), for example, in a grid pattern with intervals in the horizontal direction and the vertical direction.
In order to acquire the dose reference value D1 in the dose reference value acquisition step S2, radiation was emitted from the radiation source 101 spaced from the planned installation position P of the shield 20 toward the first side without the shield 20. Specify the dose value at the inspection position M in the case. Acquisition of the reference value D1 of the dose at each of the plurality of examination positions M is performed based on the distance L between the radiation source 101 and each examination position M and the dose distance correlation data K. FIG. Specifically, the distance L between each inspection position M and the position R where the collimator 101c of the radiation source 101 is installed can be calculated from design drawing information or the like. By referring to the dose-distance correlation data K as shown in FIG. 7 based on the calculated distance L at each inspection position M, the reference value D1 of the dose corresponding to the distance L at each inspection position M can be specified. .

In the shield installation step S3, the shield 20 is installed at a predetermined location. As shown in FIG. 2, the shield 20A is formed by pouring concrete with a predetermined thickness on a steel plate 21 and curing it for a predetermined period to form a concrete layer 22. As shown in FIG. As shown in FIG. 3, the shield 20B is formed by pouring and filling concrete between a pair of steel plates 23 horizontally spaced apart from each other, and curing for a predetermined period to form a concrete layer 24. Form.

In the passing dose detection step S4, as shown in FIG. 8, with the shield 20 installed, the radiation dose emitted from the collimator 101c and passed through the shield 20 is detected by the detector 102 at a plurality of inspection positions M. actually detected.
This involves placing a radiation source 101 at a position R on a first side of the shield 20 and a detector 102 on a second side of the shield 20 . The collimator 101c of the radiation source 101 can be easily and accurately positioned at the position R by setting it in accordance with the marking performed in the dose reference value acquisition step S2.

The detector 102 is brought into close contact with the surface 20 f of the shield 20 on the second side. The detector 102 is first arranged at an inspection position M1 facing the collimator 101c across the shield 20, for example.
In this state, the detector 102 detects a passing dose D2 of radiation emitted from the radiation source 101 and passed through the shield 20 .

Next, while the radiation source 101 is fixed at the position R, the position of the detector 102 is moved in the plane along the surface 20 f on the second side of the shield 20 . Specifically, the detector 102 is moved to an inspection position M2 separated from the inspection position M1 by a predetermined dimension, for example, 50 mm, within a plane along the surface 20f. In this state, the passing dose D2 of radiation emitted from the collimator 101c of the radiation source 101 is detected by the detector 102 at the inspection position M2.

After that, the position of the detector 102 is moved by a predetermined distance within the plane along the surface 20f, and the detection of the passing dose D2 at each inspection position M is sequentially repeated.
In this manner, the radiation dose emitted from the collimator 101c of the radiation source 101 fixed at the position R is actually detected by the detector 102 at a plurality of inspection positions M. FIG.

In FIG. 8, as the shield 20, a shield 20B installed in the vertical direction is exemplified. When the shield 20 is the shield 20A extending in the horizontal direction, the radiation source 101 and the detector 102 arrange the shield 20 on the first side and the second side in the vertical direction to detect the passing dose D2. conduct.

The attenuation rate acquisition step S5 acquires the attenuation rate DL of radiation by the shield 20 . For this, based on the passing dose D2 at a plurality of inspection positions M detected in the passing dose detection step S4 and the dose reference value D1 at each inspection position M acquired in the dose reference value acquisition step S2, each inspection position Calculate the attenuation factor DL in M.
The attenuation rate DL is calculated from the ratio of the detected value (passing dose D2) in the passing dose detection step S4 to the reference value D1 of the dose at the plurality of acquired inspection positions M.
i.e.
Attenuation rate DL=D2/D1
is.

Here, in the correlation data acquisition step S1, the space dose D3 in the space S without the shield 20 may be detected. In this case, the detection value (dose reference value D1) in the dose reference value obtaining step S2 and the detection value (passing dose D2) in the passing dose detection step S4 are each corrected with the air dose D3. i.e.
Attenuation rate DL = (D2-D3)/(D1-D3)
can be

In the determination step S6, it is determined whether or not the attenuation rates DL at the plurality of inspection positions M of the shield 20 acquired in the attenuation rate acquisition step S5 are equal to or less than a predetermined attenuation rate threshold. When the attenuation rate DL at all inspection positions M is equal to or less than a predetermined threshold, it is determined that the radiation shielding performance of the shield 20 to be inspected satisfies a predetermined standard. If the attenuation rate DL at at least some of all inspection positions M is equal to or greater than a predetermined threshold, it is determined that the radiation shielding performance of the shield 20 to be inspected does not meet a predetermined standard. do. Here, the shield 20 may be set with a plurality of types of required radiation shielding performance depending on its installation location, application, and the like. In this case, a plurality of “predetermined attenuation rate threshold values” are set according to the type of radiation shielding performance required of the shield 20 .

In the inspection of the radiation shielding performance of the shields 20 in this embodiment, the shields 20 (shields 20A and 20B) that partition the space S are each sequentially subjected to the series of steps S1 to S6.

As described above, in the method for inspecting the shield 20 of this embodiment, the correlation between the distance L from the radiation source 101 and the dose is previously obtained as the dose-distance correlation data K in the correlation data obtaining step S1. In the dose reference value acquisition step S2, the reference value D1 of the dose at a plurality of examination positions M when radiation is emitted from the radiation source 101 is calculated from the distance L between the radiation source 101 and each examination position M and the dose distance correlation obtained based on the data K. As a result, at each of a plurality of inspection positions M having different distances L from the radiation source 101, the reference value D1 of the dose in the state where the shield 20 is not installed can be obtained without actually measuring the dose. , can be obtained easily. Therefore, before the shield 20 is installed, radiation is emitted from the radiation source 101 to a plurality of inspection positions M, and the effort of measuring the reference value D1 of the dose in a state where the shield 20 is not installed can be reduced. can.

In the passing dose detection step S<b>4 of this embodiment, the passing dose D<b>2 of radiation emitted from the radiation source 101 is detected at the inspection position M on the second side of the shield 20 . In this dose reference value acquisition step S2, the dose reference values D1 are acquired at a plurality of examination positions M having different distances L from the radiation source 101 . Therefore, even if the distances L between the detector 102 and the radiation source 101 are different at a plurality of examination positions M in the passing dose detection step S4, the attenuation rate DL can be obtained in the attenuation rate obtaining step S5. Accordingly, when detecting the passing dose D2 at each inspection position M, there is no need to move both the detector 102 and the radiation source 101 to the inspection position M, and only the detector 102 is moved to the inspection position M. should be placed. Therefore, the need to move the radiation source 101 according to the inspection position M and accurately adjust the positional relationship with the detector 102 is suppressed. As a result, it is possible to efficiently inspect the shield 20 .

In the passing dose detection step S4 of this embodiment, the shield 20 can be efficiently inspected by detecting passing doses at a plurality of inspection positions M while the radiation source 101 is fixed.

In the correlation data acquisition step S1 of this embodiment, the dose D0 when radiation is actually emitted is detected at a plurality of positions X along the virtual plane V, and the doses at other positions are interpolated by calculation. Dosage-distance correlation data K is acquired by doing. As a result, when obtaining the dose-distance correlation data K, the number of positions X at which radiation is actually emitted and doses are detected can be reduced. This also makes it possible to efficiently inspect the shield 20 .

(Modification of embodiment)
In the correlation data acquisition step S1 of the above embodiment, the dose D0 is detected when radiation is emitted at a plurality of positions X along the virtual plane V, but the present invention is not limited to this.
FIG. 9 is a diagram showing a method of detecting at a plurality of positions in which the distance from the radiation source is linearly changed in the correlation data acquisition step of the modified example of the shield inspection method.
As shown in FIG. 9, in the correlation data acquisition step S1 of this modified example, the radiation dose D0 is detected at a plurality of positions X' obtained by linearly changing the distance L' of the radiation source 101 from the collimator 101c.
This is done by first placing the detector 102 at a position X′1 at a first distance L′1 from the collimator 101c of the radiation source 101 . After that, the dose D0 of radiation emitted from the collimator 101c of the radiation source 101 is detected by the detector .

Next, the position of the detector 102 is moved to a position spaced apart from (or close to) the collimator 101c by a predetermined distance from the position X′1, and a second distance from the collimator 101c different from the first distance L′1 is obtained. at a position X'2 at a distance L'2. At the position X'2, the detector 102 detects the dose D0 of radiation emitted from the collimator 101c of the radiation source 101. FIG.

Thereafter, the detector 102 is linearly moved from the collimator 101c of the radiation source 101 by a predetermined distance, and the dose D0 of the radiation emitted from the collimator 101c is detected at each position X', which is sequentially repeated.
In this way, the dose D0 of radiation emitted from the collimator 101c of the radiation source 101 fixed at the position R is detected at a plurality of positions X' in which the detector 102 is linearly changed.

Next, in the correlation data acquisition step S1, the correlation between the distance L′ from the radiation source 101 and the dose D0 of the radiation emitted from the radiation source 101 is calculated based on the dose D0 detected at each of the plurality of positions X′. The shown dose-distance correlation data is acquired by calculation. For this, based on the correlation between the distance L' from the collimator 101c of the radiation source 101 at each of the plurality of positions X' and the dose D0 detected at the plurality of positions X', obtains the dose at another position with a different distance L' (for example, a position between the position X'1 and the position X'2) by calculating it with an appropriate interpolation formula.
In this way, the dose-distance correlation data K as shown in FIG. 7 are obtained.

In the correlation data acquisition step S1 of this modified example, the dose D0 when the radiation is actually emitted is detected at a plurality of positions X' in which the distance L' from the radiation source 101 is linearly changed, and other As for the dose at the position of , the dose-distance correlation data K is obtained by interpolating by calculation. Thereby, when acquiring the dose-distance correlation data K, it is possible to suppress the number of positions X' where radiation is actually emitted and the dose is detected.
Also, in order to detect the dose D0 at a plurality of positions X', the detector 102 may be moved linearly so that the distances L' from the radiation source 101 are different. Compared to moving the detector 102 along the virtual plane V as in the above embodiment, the movement and arrangement of the detector 102 can be easily performed. This makes it possible to inspect the shield 20 more efficiently.

(Other modifications)
It should be noted that the present invention is not limited to the above-described embodiment, and includes various modifications to the above-described embodiment within the scope of the present invention. That is, the specific shapes, configurations, and the like given in the embodiments are merely examples, and can be changed as appropriate.
For example, in the above embodiment, in the passing dose detection step S4, the passing dose D2 of the radiation emitted from the radiation source 101 is detected at the inspection position M on the second side of the shield 20.
At a plurality of inspection positions M on the second side of the shield 20, the radiation dose D2 may be detected simultaneously.

Further, for example, in the above embodiment, the shields 20A and 20B are illustrated as the shields 20, but the structure and shape are not limited to those described above. For example, even if the surface shape of the first side or the second side of the shield 20 is uneven, the inspection method of the shield 20 described above can be applied.

20, 20A, 20B Shield 20f Surface 21 Steel plate 22, 24 Concrete layer 22P, 24P Paraffin layer 23 Steel plate 101 Radiation source 101a Radiation source container 101b Transmission pipe 101c Collimator 102 Detector D0 Dose D1 Reference value D2 Passing dose D3 Space dose DL Attenuation rate K Dose distance correlation data L Distances M, M1, M2 Inspection position P Planned installation position S Space S1 Correlation data acquisition step S2 Dose reference value acquisition step S3 Shield installation step S4 Passing dose detection step S4 Dose detection step S5 Attenuation rate Acquisition step S6 Judgment step V Virtual plane X, X' position

Claims (3)

A method for inspecting a shield that shields radiation,
a correlation data obtaining step of obtaining dose-distance correlation data indicating a correlation between a distance from a radiation source and a dose of radiation emitted from the radiation source;
When radiation is emitted from the radiation source spaced apart from the installation position of the shield to be installed on the first side of the installation position, the distance from the radiation source set on the second side of the installation position is different from each other. a dose reference value obtaining step of obtaining a reference dose value at each of a plurality of different examination positions based on the distance between the radiation source and each examination position and the dose distance correlation data;
The radiation source is arranged on a first side of the shield installed at the installation position, the detector is arranged on a second side of the shield, and the plurality of inspection positions on the second side of the shield. In each of the above, a passing dose detection step of detecting, by the detector, a passing dose of the radiation emitted from the radiation source that has passed through the shield;
At each of the examination positions where the passing dose is detected in the passing dose detection step, based on the dose reference value obtained in the dose reference value obtaining step and the passing dose detected in the passing dose detection step, an attenuation rate acquisition step of acquiring an attenuation rate of radiation by the shield;
and a determination step of determining whether the attenuation rate is equal to or less than a predetermined threshold. The passing dose detection step includes
2. The method of inspecting a shield according to claim 1, wherein passing doses are detected at a plurality of inspection positions while the radiation source is fixed. The correlation data acquisition step includes:
The dose when radiation is emitted from the radiation source is measured at a plurality of positions along a virtual plane corresponding to the surface of the second side of the shield to be installed at the installation position, or the distance from the radiation source is a straight line detected at multiple positions with
Calculating the dose at another position different in distance from the plurality of positions based on the detected dose value at each of the plurality of positions and the correlation of the distance between each of the positions and the radiation source The method for inspecting a shield according to claim 1 or 2, wherein the dose-distance correlation data is obtained by:

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