JP7223728B2 - Radioactive contamination inspection device - Google Patents

Description

TECHNICAL FIELD The present disclosure relates to an apparatus for measuring surface contamination by radioactive substances of different shapes to be inspected with high accuracy, and particularly to a radioactive contamination inspection apparatus suitable for inspecting the presence or absence of contamination by α-rays. .

According to the Ionizing Radiation Hazards Prevention Ordinance, when radioactivity is handled with a dose rate exceeding a certain value at the site boundary, a controlled area is established, and when items are taken out of the controlled area, they are inspected for radioactive contamination. is stipulated. For this reason, in nuclear-related facilities, an article carry-out monitor is used.

Alpha rays, which are one type of radiation, have a very weak penetrating power, and their range in air is several centimeters. It has the characteristic of being easily blocked by Therefore, detection of α-ray emitting nuclides requires the ZnS (Ag) scintillation detector to be brought into almost close contact with the inspection object, making measurement very difficult depending on the shape of the inspection object.

On the other hand, it is necessary to bring the detector close to the object to be detected, but if the detector is brought into contact with the object to be inspected, the detector itself may be contaminated.

Here, there is the following prior art as a radiation measuring apparatus that detects α-rays (see, for example, Patent Document 1). The radiation measurement apparatus according to Patent Document 1 includes a measurement chamber containing an object to be measured, an ion collector for collecting ionized ions generated by radiation from the object to be measured, and a gas circulating between the measurement chamber and the ion collector. and an ion current measurement unit for measuring the ion current value of the ions collected in the ion collection unit.

Furthermore, the radiation measurement apparatus according to Patent Document 1 includes a shape data input unit for inputting shape data of the object to be measured, and transfer of ionized ions from the upstream end of the object to be measured to the ion collecting unit based on the shape data. An ion transfer time calculation unit that calculates time, and a correction coefficient calculation unit that obtains a correction coefficient for correcting the ion current value from the ratio of the number of ions that decrease due to ion recombination in the gas during the transfer time and the shape data. and a radiation dose conversion unit that converts the ion current value into a radiation dose using the correction coefficient.

With such a configuration, the radiation measuring apparatus according to Patent Document 1 realizes a radiation measuring apparatus capable of measuring the radiation intensity of measurement objects having different shapes.

JP 2012-127796 A

However, the prior art has the following problems.
In Patent Document 1, air containing electron ion pairs ionized by α-rays emitted from an object to be inspected placed in an inspection room is guided to a measurement room, and a high voltage is applied in the measurement room to detect electrons in the air. The presence or absence of contamination is determined by collecting the ion pairs on the electrode and collecting them as charges, and measuring the charges.

In this way, the air containing electron-ion pairs is led from the inspection room to the measurement room in order to measure the contamination inside the piping, which is difficult to apply voltage from the outside, and in various ways when applying voltage. This is because the shape of the test object complicates the shape of the electric field, makes it difficult to select the optimum voltage, and makes it impossible to apply a voltage that efficiently collects electron-ion pairs.

However, it takes a certain amount of time to guide the air into the measurement chamber. If it takes a long time, the generated electron-ion pairs will recombine, making it difficult to perform accurate measurements even if correction is performed. Furthermore, in order to introduce air from the examination room to the measurement room, there is also the problem that air circulation equipment such as a blower is required.

The present disclosure has been made to solve the above-described problems, suppressing deterioration in the calculation accuracy of the amount of radioactive contamination due to recombination of electron-ion pairs, An object of the present invention is to obtain a radioactive contamination inspection device capable of measuring the intensity with high precision.

A radioactive contamination inspection apparatus according to the present disclosure includes a shape measuring unit that measures the surface shape of an object to be inspected for the amount of radioactive contamination, and an electron ion pair that is ionized and generated by radiation emitted from the object to be inspected. Based on the measurement result of the electrode and the shape measurement unit, the position of the electrode is adjusted so that the distance from the surface shape is within the allowable distance range, and based on the electron ion pair amount collected by the electrode The object to be inspected and the electrode are placed in the same inspection room, and the electrode collects electron ion pairs generated by being ionized by α-rays. It is an electrode included in the detector, and the controller calculates the electric field strength in the vicinity of the inspection object based on the measurement result by the shape measurement unit, and efficiently generates electron-ion pairs according to the calculated electric field strength. The applied voltage value for collection and the distance between the test object and the electrode are determined, the electrodes are aligned so that the determined distance is obtained, and the determined applied voltage value is applied between the test object and the electrode. Alternatively, by applying between the examination room and the electrode, electron ion pairs are collected, and based on the collection result, the α-ray dose emitted from the inspection object is calculated as the amount of radioactive contamination.

According to the present disclosure, a radioactive contamination inspection capable of suppressing deterioration in the calculation accuracy of the amount of radioactive contamination due to recombination of electron-ion pairs and measuring the radiation intensity of an inspection object having a different shape with high accuracy You can get the device.

1 is a diagram for explaining the overall configuration of a radioactive contamination inspection apparatus according to Embodiment 1 of the present disclosure; FIG. FIG. 4 is an image diagram when scanning electrodes along the surface shape of an inspection object in the first embodiment of the present disclosure; FIG. 5 is an image diagram showing how to grasp the shape of an inspection object when a 3D scanner is used as a shape measuring unit in Embodiment 1 of the present disclosure; FIG. 4 is an image diagram showing how to grasp the shape of an inspection object when a light emitting element group and a light receiving element group are used as a shape measuring unit in Embodiment 1 of the present disclosure; FIG. 4 is an image diagram showing a state in which the electrodes are scanned along the surface shape of the inspection object in the first embodiment of the present disclosure; FIG. 6 is an image diagram different from FIG. 5 showing a state in which the electrodes are scanned along the surface shape of the inspection object in the first embodiment of the present disclosure; FIG. 4 is a diagram for explaining a proportional counter region in Embodiment 1 of the present disclosure; FIG. 4 is a flowchart relating to processing for calculating the amount of radioactive contamination according to Embodiment 1 of the present disclosure;

Preferred embodiments of the radioactive contamination inspection apparatus of the present disclosure will be described below with reference to the drawings.

Embodiment 1.
[Overview of technical features]
First, an overview of the technical features of the radioactive contamination inspection apparatus according to the present disclosure will be described with reference to FIG. FIG. 1 is a diagram for explaining the overall configuration of a radioactive contamination inspection apparatus according to Embodiment 1 of the present disclosure. As shown in FIG. 1, the radioactive contamination inspection apparatus according to the first embodiment includes a shape measuring section 11, an electrode 12, an electrode driving section 13, a controller 14, and a display 21. As shown in FIG.

The shape measurement unit 11 measures the surface shape of the inspection object 1, which is the target for measuring the amount of radioactive contamination. The electrode 12 is a detector for collecting electron ion pairs ionized by radiation emitted from the inspection object 1 . The electrode driving unit 13 scans the electrode 12 along the shape of the inspection object 1 measured by the shape measuring unit 11 (while maintaining a predetermined distance from the inspection object 1). Based on the result of measurement by the shape measuring unit 11, the controller 14 issues an alignment command to the electrode driving unit 13 so that the distance from the surface shape is within the allowable distance range. The amount of radioactive contamination emitted from the inspection object 1 is calculated based on the amount.

The radioactive contamination inspection apparatus according to the first embodiment has the following features 1 and 2 in order to solve the problems of the prior art.

<Feature 1: Method for collecting electron-ion pairs>
In the radioactive contamination inspection apparatus according to the present disclosure, an inspection room for containing the inspection object 1 and a measurement room for collecting electron ion pairs by applying a voltage are not provided separately, and in the inspection room where the inspection object 1 is placed, It has a configuration in which a voltage is directly applied and electron ion pairs are collected by the electrode 12 . That is, the electrode 12 is provided at the same place as the inspection room in which the inspection object 1 is placed, and is configured to be able to directly apply a voltage to the inspection object 1 in the inspection room.

With such a configuration, there is no need for a mechanism for guiding air containing electron-ion pairs from the examination room to the measurement room. Furthermore, by eliminating the transfer time for introducing the air containing the electron-ion pairs from the examination room to the measurement room, it is possible to suppress deterioration in the calculation accuracy of the amount of radioactive contamination due to recombination of the electron-ion pairs.

<Feature 2: Setting the optimum inspection conditions according to the surface shape of the inspection object 1>
As a countermeasure against changes in the electric field depending on the shape of the inspection object 1 , the controller 14 calculates the electric field strength in the vicinity of the inspection object 1 based on the recognition result of the surface shape of the inspection object 1 by the shape measuring unit 11 .

Furthermore, the electrode driving unit 13 scans the electrode 12 along the surface shape of the inspection object 1 at the optimum electric field intensity position according to the electric field intensity calculated by the controller 14, and efficiently collects electron-ion pairs. . By adopting a method of scanning the surface of the inspection object 1 using the electrodes 12 that are smaller than the inspection object 1 , the controller 14 can identify the contamination positions on the inspection object 1 .

FIG. 2 is an image diagram when scanning the electrode 12 along the surface shape of the inspection object 1 in the first embodiment of the present disclosure. As exemplified in FIG. 2, based on the command from the controller 14, the electrode driving unit 13 scans the electrode 12 along the surface shape of the inspection object 1, and can efficiently collect electron-ion pairs. .

If it is known whether the material of the inspection object 1 is a conductor, an insulator, or a dielectric, the controller 14 can calculate the electric field. However, if the material of the inspection object 1 is unknown or if the inspection object 1 is a mixture, the controller 14 scans the electrodes 12 at a predetermined distance from the inspection object 1 .

In this way, the controller 14 calculates the electric field in the vicinity of the inspection object 1, and adjusts the distance between the inspection object 1 and the electrodes and the voltage applied to the electrodes in order to efficiently collect electron ion pairs. can be selected.

[Regarding shape recognition of inspection object 1]
Next, a specific method of recognizing the shape of the inspection object 1 by the shape measuring unit 11 will be described. In order to more accurately detect α-rays emitted from the inspection object 1, it is important to bring the electrode 12 for charge collection as close to the inspection object 1 as possible. For this purpose, the shape measuring unit 11 recognizes the surface shape of the inspection object 1 by any of the following methods 1 to 3.

<Method 1: Surface shape recognition method by 3D scanner>
The shape measuring unit 11 irradiates the inspection object 1 with a laser beam and measures the angle of reflection of the laser beam by a triangulation method or by a TOF method of measuring the time until the reflected light returns. It can recognize the distance to 1.

Therefore, the shape measurement unit 11 continuously performs such measurements at different positions and synthesizes the point data, thereby creating the three-dimensional shape of the inspection object 1 by synthesizing the point cloud data. . Such a method can be realized by using a 3D scanner as the shape measuring unit 11. FIG.

FIG. 3 is an image diagram showing grasping of the shape of the inspection object 1 when a 3D scanner is used as the shape measuring unit 11 in the first embodiment of the present disclosure. By scanning the upper portion of the inspection object 1 with a 3D scanner, the three-dimensional shape of the inspection object 1 can be obtained. If the inspection object 1 has an elongated shape, the three-dimensional shape of the inspection object 1 can be obtained by moving the inspection object 1 at a constant speed without scanning with a 3D scanner. .

<Method 2: Surface shape recognition method using light emitting element group and light receiving element group>
FIG. 4 is an image diagram showing how the shape of the inspection object 1 is grasped when the light emitting element group and the light receiving element group are used as the shape measuring unit 11 in the first embodiment of the present disclosure. As shown in FIG. 4, the shape measurement unit 11 scans the inspection object 1 with a group of sensors in which a plurality of light emitting elements and a plurality of light receiving elements are arranged so as to face each other. Slice data of the inspection object 1 can be obtained.

By performing such scanning in the X direction and the Y direction, the shape measurement unit 11 can specify the surface shape of the inspection object 1 . Compared to Method 1, Method 2 has the advantage of being able to identify the surface shape with an inexpensive configuration.

<Method 3: Surface Shape Recognition Method Using Image of Inspection Object 1>
The surface shape of the inspection object 1 can also be recognized by using an image processing device as the shape measuring unit 11 . In this case, the shape measuring unit 11 can specify the surface shape of the inspection object 1 by taking a photograph of the inspection object 1 and performing image processing on the taken image.

[Specification of the position of the electrode 12 and the applied voltage based on the surface shape of the inspection object 1]
Next, based on the measurement result of the surface shape of the inspection object 1 by the shape measuring unit 11, the distance between the inspection object 1 and the electrode 12 and A method for determining the applied voltage of is described.

The controller 14 receives the measurement results regarding the surface shape of the inspection object 1 by the shape measuring unit 11 . Then, if the material of the inspection object 1 is known, the controller 14 can calculate the electric field intensity for each vicinity of the surface position of the inspection object 1 .

Furthermore, the controller 14 can determine the applied voltage value and the distance between the test object 1 and the electrode 12 for efficiently collecting electron-ion pairs according to the calculated electric field strength. Then, the controller 14 controls the electrode drive unit 13 so as to achieve the determined distance, thereby aligning the electrodes 12 included in the α-ray detector, and applying the determined applied voltage value to the inspection object 1 and the electrodes. 12, or between the examination chamber and the electrode 12.

In addition, there may be a case where the surface shape of the inspection object 1 is complicated and the electric field intensity cannot be calculated. In this case, the controller 14 determines the distance between the inspection object 1 and the electrode 12 when scanning the electrode 12 and the applied voltage so that the charge can be efficiently collected and the distance between the inspection object 1 and the electrode 12 is By determining the distance and the voltage at which discharge does not occur between them offline, the values determined offline can be adopted.

[Regarding scanning method and charge collection method of electrode 12]
Next, a specific method of collecting charges while scanning the electrodes 12 will be described.
The controller 14 performs voltage control so as to apply the determined applied voltage to the electrodes 12 and performs scanning control of the electrodes 12 so that the electrodes 12 are kept at a constant distance from the inspection object 1 . As a result, the electrode 12 can collect electrons and ions ionized by α-rays at each scanning position.

FIG. 5 is an image diagram showing a state in which the electrode 12 is scanned along the surface shape of the inspection object 1 in the first embodiment of the present disclosure. FIG. 5 shows the inspection object 1 as viewed from the side. The controller 14 scans so that the electrode 12 maintains a constant distance from the inspection object 1, as shown in FIG.

If the inspection object 1 is contaminated with α-rays, the electron-ion pairs ionized by the α-rays will gather at the electrode. Therefore, the controller 14 detects the degree of contamination by measuring the charge amount collected by the electrode 12 if the inspection object 1 is contaminated by α-rays while scanning the electrodes to which the voltage is applied. can be done.

FIG. 6 is an image diagram different from FIG. 5 showing a state in which the electrode 12 is scanned along the surface shape of the inspection object 1 in the first embodiment of the present disclosure. FIG. 6 shows the inspection object 1 as viewed from above. The size of the electrode 12 can be changed according to the size of the inspection object 1 and the surface shape of the inspection object 1 . Moreover, the detection sensitivity can be adjusted by variably setting the scanning speed of the electrodes and the integration time of the charges.

The scanning speed of the electrode 12 will depend on the collection time during which the charge generated by the alpha rays can be efficiently collected. However, since the moving speed of electric charges is high, the scanning speed is set as a feasible scanning speed in consideration of safety in the electrode drive system. In other words, the scanning speed is selected such that the electrode 12 does not come into contact with the unevenness of the inspection object 1 .

The inside of the inspection chamber in which the object 1 to be inspected is placed may be at atmospheric pressure. However, if the electron-ion pair collection efficiency is low at atmospheric pressure and a stable output cannot be obtained, it is conceivable to seal the counting gas in the examination chamber and apply a voltage to the electrodes to cause gas amplification.

FIG. 7 is a diagram for explaining a proportional counter region according to Embodiment 1 of the present disclosure. In FIG. 7, the horizontal axis indicates the applied voltage, and the vertical axis indicates the number of electron-ion pairs. By enclosing the counting gas, the electrode 12 and the test object 1 act as a proportional counter tube and have a proportional counter area in which the vertical axis and the horizontal axis are in a proportional relationship, as shown in FIG. Therefore, by applying a voltage that causes gas amplification to the electrodes, the amount of electron-ion pairs collected by the electrodes 12 can be increased and the output can be stabilized.

[Presence or absence of contamination and calculation of contamination concentration]
Next, a specific method for calculating the position and concentration of contamination on the inspection object 1 from the collected charge amount will be described. If all electron-ion pairs ionized by α-rays can be collected in the electrode, the number of α-rays per unit area can be evaluated as the amount of α-rays emitted from the inspection object 1 from the amount of charge obtained as the collection result. . However, in practice, the collection efficiency does not reach 100% due to recombination of electron-ion pairs and the like.

Therefore, in order to grasp the detection efficiency in advance and accurately calculate the contamination concentration (Bq/cm ² ), a simulated contamination source composed of a plurality of standard radiation sources is used to determine the concentration of the contamination source and the amount of collected charge. It is conceivable to specify in advance the relationship between The relationship between the concentration of the pollution source specified in advance and the collected charge amount can be set in advance as a table or a calculation formula. Therefore, the controller 14 can easily convert the charge amount collected by the electrode 12 into the contamination concentration by using a preset table or formula.

[Display of test results]
The controller 14 can compare the calculated contamination concentration to a predetermined alarm setpoint and issue an alarm if the contamination concentration exceeds the alarm setpoint. In addition, the controller 14 can cause the display 21 to display the calculated contamination concentration, alarm message, and the like.

Summarizing the above contents, according to the radioactive contamination inspection apparatus according to the first embodiment, the following effects can be realized.
(Effect 1) It is possible to directly collect electron-ion pairs generated in the vicinity of the object to be inspected. For this reason, the detection error of radioactive contamination can be suppressed to a small amount, and correction processing associated with recombination is not required, and a transfer device can be eliminated.

(Effect 2) It is possible to collect electron ion pairs at a plurality of different positions along the surface shape of the inspection object using relatively small electrodes, and to calculate the amount of radioactive contamination at each different position. . Therefore, it is possible to identify the contaminated portion of the object to be inspected based on the calculation result, and to detect contamination with high efficiency and high accuracy of charge collection.

(Effect 3) Since electron-ion pairs generated in the vicinity of the object to be inspected are directly collected, only the space between the object to be inspected and the electrode is subject to background. As a result, it is possible to perform the radioactive contamination inspection while suppressing the influence of the background, and improve the inspection accuracy.

(Effect 4) The shape and size of the electrodes for voltage application and charge collection can be appropriately selected according to the measurement result of the surface shape of the inspection object. As a result, by using an appropriately selected electrode, it is possible to apply it to various inspection objects, and it is possible to measure the radiation intensity of inspection objects having different shapes with high accuracy.

(Effect 5) By measuring the surface shape of the object to be inspected, the electric field strength in the vicinity can be calculated. Thus, up to a maximum voltage that does not cause a discharge can be applied to the electrodes and charge can be collected in the proportional counter region.

Finally, a method for calculating the amount of radioactive contamination by the radioactive contamination inspection apparatus according to the first embodiment described above will be described using a flowchart.

FIG. 8 is a flowchart relating to processing for calculating the amount of radioactive contamination according to Embodiment 1 of the present disclosure. In step S<b>801 , the shape measurement unit 11 measures the surface shape of the inspection object 1 .

Next, in step S<b>802 , the controller 14 calculates the electric field intensity near the inspection object 1 based on the measurement result of the surface shape of the inspection object 1 by the shape measuring unit 11 . Furthermore, the controller 14 determines the distance between the electrodes and the test object 1 and the applied voltage according to the calculated electric field strength.

It is also possible to change the shape and size of the electrodes as necessary based on the measurement result of the surface shape of the inspection object 1 . Further, with respect to the processing of steps S801 and S802, it is possible to perform data processing in advance as off-line.

Next, in step S<b>803 , the controller 14 scans the small electrodes along the surface shape of the inspection object 1 .

Next, in step S804, the controller 14 collects charges for each scanning position via the electrodes 12 and stores them as detection data in the storage unit.

Finally, in step S805, the controller 14 calculates the contamination concentration at each scanning position based on the amount of charge collected for each scanning position. At this time, the controller 14 can use a preset table or formula to convert the amount of charge collected to the concentration of contamination.

Furthermore, the controller 14 can compare the calculated contamination concentration with the alarm set value, and display an alarm via the display 21 when the contamination concentration exceeds the alarm set value.

As described above, according to Embodiment 1, deterioration in the calculation accuracy of the amount of radioactive contamination due to recombination of electron-ion pairs is suppressed, and the radiation intensity of inspection objects having different shapes is measured with high accuracy. It is possible to realize a radioactive contamination inspection apparatus that can

In the above-described embodiment, the radioactive contamination inspection device suitable for contamination inspection by α-rays was mainly described, but the radioactive contamination inspection device according to the present disclosure is also applicable to radiation other than α-rays. It is possible. In other words, the technical idea of identifying the contamination position on the inspection object by using a smaller electrode than the inspection object and scanning the surface of the inspection object is the is also applicable.

1 test object, 11 shape measuring section, 12 electrode, 13 electrode driving section, 14 controller, 21 display.

Claims (4)

a shape measuring unit for measuring the surface shape of an object to be inspected for radioactive contamination;
an electrode for collecting electron ion pairs ionized by radiation emitted from the inspection object;
Aligning the electrodes so that the distance from the surface shape is within the allowable distance range based on the measurement result by the shape measuring unit, and based on the amount of electron ion pairs collected by the electrodes, the inspection object and a controller for calculating the amount of radioactive contamination of an object ,
The test object and the electrode are placed in the same examination room, and the electrode is an electrode included in an α-ray detector that collects electron ion pairs generated by being ionized by α-rays. , the controller calculates an electric field strength in the vicinity of the inspection object based on the measurement result by the shape measurement unit, and applies an electric field strength for efficiently collecting the electron-ion pairs according to the calculated electric field strength. A voltage value and a distance between the inspection object and the electrode are determined, the electrodes are aligned so as to achieve the determined distance, and the determined applied voltage value is applied to the inspection object and the electrode. By applying between or between the examination room and the electrode, the electron ion pair is collected, and the α-ray dose emitted from the inspection object based on the collection result is used as the radioactive contamination amount calculate
Radioactive contamination inspection equipment. the size of the electrode is smaller than the size of the surface shape of the inspection object;
The controller performs the alignment of the electrodes so that the distance from the surface shape is within the allowable distance range at a plurality of different positions with respect to the inspection object, and at each of the plurality of different positions The radioactive contamination inspection apparatus according to claim 1, wherein the amount of radioactive contamination is calculated, and a contaminated portion of the inspection object is specified based on the calculation result. 3. The radiation according to claim 1 or 2, wherein the α-ray detector selects an electrode shape suitable for collecting the electron-ion pair according to the measurement result by the shape measuring unit and the determined distance. contamination inspection equipment. The controller collects the electron-ion pairs while scanning the electrodes along the surface topography of the inspection object while aligning the electrodes to achieve the determined distance. 4. A radioactive contamination inspection apparatus according to any one of claims 1 to 3, wherein the amount of alpha rays emitted from the object is calculated.

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