JP4891972B2 - Calibration equipment for radioactive contamination monitoring - Google Patents

Description

  The present invention relates to a calibration device for a monitor for measuring radioactive contamination of an object, and more particularly to a mechanism for self-running a calibration radiation source.

  In radioactive material handling facilities such as nuclear power plants and nuclear fuel processing facilities, it is necessary to confirm the presence of radioactive contamination in clothing worn by workers (coveralls, hats, socks, etc.). The confirmation is generally performed using a clothing monitor or a laundry monitor. Such monitoring may be performed after the clothes are washed and dried, or may be performed before the clothes are washed. In addition to clothing monitors, article monitors that measure radiation contamination of tools and the like are also known. Both the clothing monitor and the article monitor are a kind of radioactive contamination monitor or surface contamination measuring device.

  The clothes monitor will be described in detail. The clothes monitor has a horizontal slit-shaped clothes conveyance path, and its width is wide enough to accept clothes, which has a size of, for example, 70 cm. A large-area radiation detector is disposed on the upper and lower sides of the clothing conveyance path in order to perform measurement while conveying clothing spread in the horizontal and vertical directions. This clothing monitor is periodically calibrated (inspected). That is, an operation state (sensitivity, counting efficiency, etc.) is confirmed using a calibration radiation source and necessary adjustments are performed. At that time, a planar surface radiation source is used, which is fed into the clothes conveyance path, and the reference radiation from the surface radiation source is detected. At that time, it is necessary to repeatedly arrange the surface ray source at various positions in the transverse direction orthogonal to the carrying direction while operating the clothes carrying mechanism and to feed the surface ray source into the clothing carrying path. In some cases, the measurement must be repeated at the same position in the horizontal direction. Conventionally, the positioning is performed manually.

Japanese Patent Laid-Open No. 7-84051

  Conventionally, as described above, since the positioning of the surface radiation source has been performed manually, there is a problem in that measurement reproducibility cannot be ensured. Moreover, there is a problem that the work is complicated. Patent Document 1 describes an article monitor, which describes feeding a unit having a mechanism for sliding a radiation source in a lateral direction into a clothing conveyance path. In the vertical direction, that is, the article conveyance direction, the conveyance mechanism provided in the article monitor is used as it is. Therefore, there are problems that the radiation source cannot be moved at an arbitrary speed and the position of the radiation source on the horizontal plane cannot be determined freely.

  Note that the apparatus described in Patent Document 1 is an article monitor, and the height of the article conveyance path is relatively large. Therefore, it is easy to insert a relatively large mechanism there, but it is thin like clothing. However, in the case of a monitor that performs measurement, since the conveyance path is slit-shaped, there is an inherent problem that a mechanism having a thickness cannot be inserted therein.

  An object of the present invention is to increase the reproducibility of calibration or reduce the burden during calibration.

  Another object of the present invention is to provide a calibration device that can freely determine the position and movement of a radiation source.

  Another object of the present invention is to realize a two-dimensional movement of the radiation source even when the measurement path is thin.

  The present invention relates to a calibration apparatus used at the time of calibration of a radioactive contamination monitor for measuring radioactive contamination of an object, an insertion portion inserted into a measurement passage in the radioactive contamination monitor, connected to the insertion portion, and the measurement passage. A non-insertion portion that is positioned outside, a radiation source holder that is provided in the insertion portion and mounts a calibration radiation source, and is provided in the insertion portion, and the radiation source holder is disposed in a first horizontal direction. A first slide mechanism that slides in the first and second non-insertion portions, and a second slide mechanism that slides in the second horizontal direction perpendicular to the first horizontal direction. A drive unit provided on the non-insertion unit and configured to drive at least one of the first slide mechanism and the second slide mechanism.

  According to the said structure, the calibration apparatus used at the time of a calibration contains the insertion part inserted in a measurement channel | path, and the non-insertion part connected with it. The first slide mechanism is a mechanism that slides the radiation source holder in the first horizontal direction, and the second slide mechanism is a mechanism that slides the first slide mechanism in the second horizontal direction. With both functions, it is possible to scan the calibration radiation source two-dimensionally. That is, it is not necessary to operate the transport mechanism included in the radioactive contamination monitor. Therefore, the movement path of the radiation source can be freely determined, and the radiation source can be positioned freely. It is also easy to change the moving speed in both the first horizontal direction and the second horizontal direction as necessary. Since it is configured as a combination of an insertion part and a non-insertion part, it is possible to install a member with a height (for example, a drive motor) in the non-insertion part and to transmit power from there. is there. In general, the non-insertion portion is installed on a loading table having an open top, but the present invention is not limited thereto. For example, it may be positioned on the carry-out stand. In any case, according to the combined use of the insertion portion and the non-insertion portion, it is possible to obtain an advantage that various mechanisms can be rationally arranged according to individual properties. In particular, the drive source is relatively large in size, but if the transmission means is used, there is a degree of freedom in its installation location, so it is reasonable to arrange it in the non-insertion portion. In any case, since the radiation source positioning in both sliding directions can be performed accurately, the reproducibility is good and the burden on the user can be greatly reduced.

  The radioactive contamination monitor in which the calibration apparatus according to the present invention is used is preferably a clothing monitor, but may be another monitor such as an article monitor. Both the first slide mechanism and the second slide mechanism may be provided in the insertion portion, or the first slide mechanism may be provided in the non-insertion portion and the second slide mechanism may be provided in the non-insertion portion. The latter is advantageous in terms of the device configuration because the height restriction can be eliminated or relaxed for the second slide mechanism.

  Preferably, the radioactive contamination monitor is a clothing monitor that measures radioactive contamination in clothing as a measurement target, the measurement passage has a slit-like shape that extends horizontally, and the insertion portion is a flat surface that extends horizontally. It has a thin plate shape. Desirably, the said non-insertion part has the form enlarged in the height direction rather than the said insertion part. Since the non-insertion part is installed outside the measurement passage, that is, it is installed in a space where there is no limit or allowance for it, the non-insertion part should be larger in the height direction than the insertion part. Rather, if the large part is mounted on the non-insertion portion as much as possible, the insertion portion can be made thinner.

  Preferably, the non-insertion portion includes a first drive portion for the first slide mechanism and a second drive portion for the second slide mechanism as the drive portion. Preferably, the first horizontal direction is a direction orthogonal to a transport direction for transporting the measurement object, the second horizontal direction is the transport direction, and the insertion portion includes the first slide mechanism and the second slide mechanism. Have Preferably, the first horizontal direction is a transport direction for transporting a measurement object, the second horizontal direction is a direction orthogonal to the transport direction, the insertion portion includes the first slide mechanism, The insertion portion has the second slide mechanism.

  Preferably, a scanning control unit that performs two-dimensional scanning of the radiation source holder in the measurement path by controlling operations of the first slide mechanism and the second slide mechanism is included. The scanning control unit may be configured by a control unit of the radioactive contamination monitor, or may be configured as a dedicated control unit different from that. Preferably, a position detector that detects a two-dimensional scanning position of the radiation source holder, and a calibration unit that calibrates the radiation detector based on a measurement result of the calibration radiation source at each of the two-dimensional scanning positions. Including. According to this configuration, calibration can be fully automated or semi-automated.

  As described above, according to the present invention, the reproducibility of calibration can be improved, or the user burden at the time of calibration can be reduced. Alternatively, the position and movement of the radiation source can be freely determined. Alternatively, the two-dimensional movement of the radiation source can be realized even when the measurement path is thin.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.

  FIG. 1 shows an example of a clothing monitor that is a kind of radioactive contamination monitor. The configuration itself is known. This clothing monitor is installed in, for example, a nuclear power plant, a nuclear fuel processing facility, etc., and the target clothing is work clothes, underwear, hats, socks, gloves, etc. worn by workers. . Clothing that has been washed and dried may be targeted, or clothing before washing may be targeted. It should be noted that the present invention can also be applied to an article monitor other than a clothing monitor.

  In FIG. 1, a clothing monitor 30 has a carry-in table 30A on which clothes are placed while being unfolded, a measurement passage 30C through which clothes are fed, and a carry-out table 30B at the subsequent stage. They are continuous in the transport direction (X direction). The measurement passage 30 </ b> C has a flat shape that narrows up and down and spreads horizontally, and has a slit-like opening extending in the horizontal direction on the carry-in side and the carry-out side. The clothing monitor 30 includes a lower transport mechanism 34 and an upper transport mechanism 36. As will be described later, these mechanisms 34 and 36 use a metal net member as a conveyor belt, thereby conveying clothes while pinching or guiding them. At the center of the clothing monitor 30, a lower detection unit 38 and an upper detection unit 40 are provided via a measurement passage 30C. These units 38 and 40 are each composed of a plurality of detectors divided in the left-right direction. They may be composed of a plurality of detectors divided in the front-rear direction or divided in the front-rear and left-right directions. There are two portions rising upward on both sides of the carry-in table 30A, and an input device (display device) 44 is provided on one of them. The lower transport mechanism 34 and the upper transport mechanism 36 perform a transport operation at a constant speed during clothing measurement, but these operations are not necessary during calibration as will be described later.

  FIG. 2 specifically shows the internal configuration of the clothing monitor 30. The lower transport mechanism 34 includes a transport belt 46 and two rollers 48 and 50. In the present embodiment, the conveyor belt 46 is constituted by a wire mesh. This is for durability and prevention of static electricity. The wire mesh is stretched around two rollers 48 and 50. The upper transport mechanism 36 includes a transport belt 52 and four rollers 54-60. The conveyor belt 52 is also composed of a wire mesh, and is stretched around four rollers 54-60. The driving directions of the conveyor belts 46 and 52 are as shown in the figure.

  As described above, the two detection units 38 and 40 are provided at the center of the clothing monitor 30. Since they basically have the same configuration, the structure of the lower detection unit 38 will be described as a representative. The lower detection unit 38 includes a shielding member 62, a scintillator plate 64 provided therein, four photomultiplier tubes (PMT) 66 for detecting light generated there, and the like. The scintillator plate 64 is divided into a plurality of parts, so that, for example, it is possible to determine the presence or absence of contamination in the four areas on the left and right and front and rear in the transport direction. Of course, the distinction may be made only on the left and right or only on the front and back. Unlike the upper detection unit 40, the lower detection unit 38 has a protection member 68. This is a member that protects the surface of the scintillator plate 64 from contamination.

  A sensor 70 is provided on the inlet side in the transport path. The sensor 70 detects the garment that has been thrown in. The sensor 70 determines that the garment has reached the position where the sensor 70 is disposed, and detects the length of the garment in the transport direction. In this embodiment, the sensor 70 includes a light emitter 70a and a light receiver 70b. That is, by forming a light beam between them, clothing can be detected by the light beam. Of course, as the sensing method, a magnetic sensor or a contact sensor can be used in addition to the optical one.

  In this embodiment, the input device 44 is constituted by a liquid crystal panel with a touch sensor. The operator inputs the type of clothes to be thrown in using the input device 44. Usually, since the same type of clothing is continuously input, if the setting is performed at the start time, it is not necessary to input the type every time each clothing is input. Of course, each input of clothing may be input. The controller 42 controls the operation of each component included in the clothing monitor 30.

  Next, a preferred embodiment of the calibration apparatus according to the present invention will be described with reference to FIGS. FIG. 3 shows the calibration device 150 as viewed from the side. The calibration device 150 is used when the clothing monitor 30 is calibrated (inspected). The calibration device 150 is roughly composed of an insertion part 152 and a non-insertion part 154. As will be described later, the insertion unit 152 functions as an XY scanning unit, and the non-insertion unit 154 is exclusively provided with a drive unit. As shown in FIG. 3, in this embodiment, the height of the non-insertion portion 154 is larger than the height (thickness) of the insertion portion 152.

  That is, the insertion portion 152 is a portion inserted into the horizontal slit-shaped measurement passage 30C, which has a thin plate shape spreading in the horizontal direction, whereas the non-insertion portion 154 has no spatial restriction. In this case, it is provided at a position outside the insertion passage 30C and opened upward, and basically has no height restriction. Therefore, it is possible to correct it with a form enlarged in the height direction.

  Incidentally, it is desirable to calibrate the insertion portion 152 as having an extent that covers the entire sensitive area by the two detection units 38 and 40. In the example shown in FIG. 3, the non-insertion portion 154 is installed on the carry-in table 30A, but it may be installed on the carry-out table 30B. FIG. 4 shows the calibration device 150 as viewed from above. The calibration device 150 is calibrated by the insertion unit 152 and the non-insertion unit 154 as described above. In the example shown in FIG. 4, the insertion unit 152 has two slide mechanisms, that is, slide mechanisms 156 and 158. The slide mechanism 156 is a slide mechanism in the X direction, and the slide mechanism 158 is a slide mechanism in the Y direction. The holder 160 holding the planar radiation source 162 is scanned in the Y direction by the slide mechanism 158. Specifically, the radiation source holder 160 slides on a rail extending in the Y direction.

  The slide mechanism 156 is a mechanism that slides the slide mechanism 158 in the X direction. Specifically, the slide mechanism 158 is scanned in the X direction by a rail that the slide mechanism 156 has. Incidentally, the slide mechanism 158 has a length close to the horizontal width of the measurement passage 30C, that is, the width in the Y direction, and the slide mechanism 164 has a length that exceeds the sensitive area by the detection unit, so that the sensitivity can be measured. The source 162 can be positioned over the entire required area or at any point within the area. That is, the two slide mechanisms 156 and 158 together constitute a two-dimensional scanning mechanism.

  The slide mechanism 156 has a mechanism for driving the slide mechanism 158, and the mechanism includes a pair of pulleys 168 and 170 and a belt 166 spanned between them. The slide mechanism 158 is also provided with a belt conveyance mechanism, but details thereof are not shown.

  The non-insertion portion 154 is provided with the pulley 168 described above, and motors 171 and 172 as drive sources. The motor 171 is a drive source for driving the slide mechanism 156, and the motor 172 is a drive source for driving the slide mechanism 158. In general, since motors, gear mechanisms, and the like have a certain amount of material, it is often difficult to arrange them in the measurement space 30C, but in this embodiment, a non-insertion unit connected to the insertion unit 152 These members can be arranged at 154. However, the entire calibration device 150 may include a flat plate shape including the non-insertion portion 154.

  In the embodiment shown in FIGS. 3 and 4, the slide mechanism 158 is supported on one side thereof, but the slide mechanism 158 may be supported on both sides thereof and may be slid. This can also be pointed out in the embodiment shown in FIG. 7 described later.

  FIG. 5 conceptually shows the scanning path of the radiation source. (A) shows a moving path of a radiation source such as a raster scan. That is, the scan 174 along the X direction can be repeatedly executed while changing the position in the Y direction. In this case, scanning in the X direction is performed from the right side to the left side, that is, from the upstream side to the downstream side, and during each scan, the radiation source is returned to the upstream side in the X direction. May be performed simultaneously. The moving path in that case is indicated by a broken line 176.

  (B) shows an example in which measurement is performed in both the forward path and the return path of the radiation source. That is, a path having a zigzag shape is shown. (C) shows a spiral path. (D) shows a path pattern in which scanning in the Y direction is the basis, and this is repeatedly executed while changing the position in the X direction.

  In the present embodiment, independent scanning mechanisms are provided for the X direction and the Y direction, respectively, and the source can be positioned at an arbitrary position on the two-dimensional plane by controlling them independently. There is an advantage that the moving speed of the source can be freely determined. Therefore, in particular, if there is a position where the drop or deterioration in sensitivity is a problem, it is easy to first perform the inspection by positioning the radiation source at that position. That is, it is possible to realize a calibration process that cannot be performed by a conventional apparatus such as multi-point spot observation.

  FIG. 6 shows a module configuration when automatic calibration or semi-automatic calibration is performed. The lower detection unit 38 includes a plurality of detectors 38A and 38B, and similarly, the upper detection unit 40 includes a plurality of detectors 40A and 40B. Each detector can detect radiation independently. Each detector may detect radiation by a so-called simultaneous coefficient method. The calibration device 150 includes an X position sensor 180 that detects the position of the radiation source in the X direction, and a Y position sensor 182 that detects the position of the radiation source in the Y direction.

  Output signals from the plurality of detectors 40A, 40B, 38A, 38B and the plurality of position sensors 180, 182 are input to the calibration controller 178. The calibration controller 178 may be a dedicated controller incorporated in the calibration apparatus shown in FIG. 1, or may be a personal computer connected to the calibration apparatus. Alternatively, the function of the calibration controller 178 may be realized by the controller 42 shown in FIG. The sensitivity distribution forming unit 184 forms a sensitivity distribution for the upper unit 40. That is, the sensitivity distribution on the two-dimensional plane is formed by associating the two-dimensional coordinates of the radiation source with the measurement values. The same applies to the sensitivity distribution forming unit 186 that receives an output signal from the lower detection unit 38, thereby forming a sensitivity distribution for the lower detection unit. The display 188 displays the sensitivity distribution for the upper detection unit and the sensitivity distribution for the lower detection unit 38, respectively. Therefore, by observing such sensitivity distribution, it is possible to immediately recognize which part has high sensitivity and which part has low sensitivity.

  The module 190 functions as a pass / fail determination unit and a sensitivity adjustment unit. That is, the module 190 determines whether or not the sensitivity of each detector is appropriate based on the two sensitivity distributions output from the sensitivity distribution forming units 184 and 186. For a detector whose sensitivity is determined to be inappropriate, the power supply voltage supplied to the detector is adjusted and the sensitivity is calibrated.

  The sensitivity adjustment is executed after the two-dimensional scanning of the radiation source is completed. Of course, the sensitivity adjustment may be performed in parallel with the movement of the radiation source. In order to confirm that the sensitivity is uniform after the sensitivity adjustment, the two-dimensional scanning of the radiation source may be performed again.

  FIG. 7 shows another embodiment. The calibration device 192 shown in FIG. 7 has an insertion portion 196 and a non-insertion portion 194 connected thereto, and the insertion portion 196 functions as an X scanning portion. On the other hand, the non-insertion part 194 has a function as a Y scanning part and a function as a drive part. That is, in the embodiment shown in FIGS. 3 and 4, both the Y-direction slide mechanism and the X-direction slide mechanism that supports the Y-direction slide mechanism are inserted into the measurement space. However, in the embodiment shown in FIG. Only the directional slide mechanism is inserted into the measurement passage 30C. On the other hand, since the Y-direction slide mechanism is positioned outside the measurement passage 30C and the height restriction is eliminated, there is an advantage that the Y-direction slide mechanism can be made robustly.

It is a schematic diagram which shows the whole structure of a clothing monitor. It is a figure which shows the internal structure of a clothing monitor. It is a side view which shows suitable embodiment of the calibration apparatus which concerns on this invention. FIG. 4 is a top view of the calibration device shown in FIG. 3. It is a figure which shows the various examples of the scanning path | route of a radiation source. It is a figure which shows the calibration controller which performs automatic calibration. It is a top view of a calibration device in other embodiments.

Explanation of symbols

  30 clothing monitor, 30A carry-in stand, 30B carry-out stand, 30C measurement path, 34 upper transport mechanism, 36 lower transport mechanism, 38 lower detection unit, 40 upper detection unit, 150 calibration device, 152 insertion section, 154 non-insertion section 156 slide mechanism, 158 slide mechanism.

Claims (8)

In a calibration device used when calibrating a radioactive contamination monitor that measures the radioactive contamination of an object,
An insertion part to be inserted into a measurement passage in the radioactive contamination monitor;
A non-insertion portion connected to the insertion portion and positioned outside the measurement passage;
Including
A radiation source holder that is provided in the insertion portion and carries a calibration radiation source;
A first slide mechanism provided in the insertion portion and configured to slide the radiation source holder in a first horizontal direction;
A second slide mechanism that is provided in the insertion part or the non-insertion part and that slides the first slide mechanism in a second horizontal direction orthogonal to the first horizontal direction;
A drive unit provided in the non-insertion unit for driving at least one of the first slide mechanism and the second slide mechanism;
A calibration apparatus for a radioactive contamination monitor, comprising: The apparatus of claim 1.
The radioactive contamination monitor is a clothing monitor that measures radioactive contamination in clothing as a measurement target;
The measurement passage has a slit-like shape extending horizontally,
The insertion part has a flat thin plate shape extending horizontally,
A calibration apparatus for a radioactive contamination monitor characterized by the above. The apparatus of claim 2.
The calibration apparatus for a radioactive contamination monitor, wherein the non-insertion portion has a form enlarged in the height direction than the insertion portion. The device according to any one of claims 1 to 3,
The non-insertion unit includes a first drive unit for the first slide mechanism and a second drive unit for the second slide mechanism as the drive unit.
A calibration apparatus for radiation contamination monitoring characterized by the above. The apparatus according to any one of claims 1 to 4,
The first horizontal direction is a direction orthogonal to the transport direction for transporting the measurement target;
The second horizontal direction is the transport direction;
The insertion portion has the first slide mechanism and the second slide mechanism,
A calibration apparatus for radiation contamination monitoring characterized by the above. The apparatus according to any one of claims 1 to 4,
The first horizontal direction is a transport direction for transporting a measurement target;
The second horizontal direction is a direction orthogonal to the transport direction;
The insertion portion has the first slide mechanism,
The non-insertion part has the second slide mechanism,
A calibration apparatus for radiation contamination monitoring characterized by the above. The device according to any one of claims 1 to 6,
A scanning control unit that performs two-dimensional scanning of the radiation source holder in the measurement path by controlling operations of the first sliding mechanism and the second sliding mechanism;
A calibration apparatus for radiation contamination monitoring characterized by the above. The apparatus of claim 7.
A position detector for detecting a two-dimensional scanning position of the radiation source holder;
A calibration unit for calibrating the radiation detector based on the measurement result of the calibration radiation source at each two-dimensional scanning position;
A calibration apparatus for a radiation contamination monitor, comprising:

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