JPH08248134A - Body-surface gate monitor - Google Patents

Abstract

PURPOSE: To obtain a body-surface gate monitor by which a constant detection efficiency is always relaized irrespective of the bodily shape of an operator by arranging a detector so as to match the bodily shape of the operator. CONSTITUTION: In a body-surface gate monitor, whether a contamination exists or not on the body surface of a subject M who has entered a monitor body from an entrance door is decided, and the subject who is not contaminated leaves from an exit door. Radiation detectors 21 are arranged on the inside wall of the monitor body and in a region which faces the front face, the rear face or the side face of the subject so as to be freely approached and retreated independently with reference to the subject, and positions of the respective radiation detectors 21 with reference to the subject are detected by position detecting sensors 64, and a drive part is controlled on the basis of positional information detected by the position detecting sensors 64. Thereby, the radiation detectors 21 are stopped at a constant distance from the position of the body surface of the subject.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is installed at an entrance / exit to a radiation controlled area in a nuclear power plant or a treatment facility for handling radioactive substances, and measures the degree of contamination of workers in order to inspect for the presence or absence of radiation contamination. Body surface gate monitor.

[0002]

2. Description of the Related Art FIG. 9 shows a configuration example of a conventional body surface gate monitor. The body surface gate monitor 1 shown in the figure includes a front detector accommodating portion 2, a rear surface detector accommodating portion 3, side surface detector accommodating portions 4, 5, a head detector accommodating portion 6, and a foot detector accommodating portion 7. It is configured. The radiation detectors 21 to 26 are housed in the front surface detector housing portion 2 facing the front surface of the worker M who has entered the gate monitor.
Radiation detectors 31 to 36 are housed in the rear surface detector housing portion 3 whose rear surfaces face each other. Radiation detectors 41 to 44 and 51 to 54 are housed in the left and right side surface detector accommodating portions 4 and 5 facing the right and left side surfaces of the worker M. The left and right side surface detector accommodating portions 4 and 5 are attached to the revolving door with respect to the left and right entrances and exits of the body surface gate monitor 1, as shown in FIG. 9C. Further, the radiation detectors 61 to 63 are accommodated in the head detector accommodating portion 6 that moves up and down according to the height of the worker M, and the radiation detectors 71 to 72 are accommodated in the foot detector accommodating portion 7. There is.

In the body surface gate monitor 1, when the worker who enters the gate monitor stands still at the measurement position and becomes ready for measurement, the radiation detector measures the radiation density on the whole body surface of the worker. . When the surface contamination density exceeds a predetermined threshold, the exit door is locked to prevent workers from leaving (meaning to go out of the radiation control area) and to give an alarm to the radiation administrator. Emit.

[0004]

However, in the above-mentioned conventional body surface gate monitor, the detection efficiency varies depending on the individual difference of the examinees, so that the detection efficiency is constant for all examinees. It was difficult to measure the pollution.

The foot detector on which the operator's foot rests and the head detector which descends according to the height of the operator can maintain a constant distance between the measurement site and the detector. Therefore, the detection efficiency is constant even among subjects of different body types. However, the detectors on the front and back surfaces and the left and right sides are different in the detection efficiency depending on the worker because the distance between the detector and the measurement site varies greatly depending on the worker's body type (obesity type, lean type). There is a problem of coming up.

For example, as shown in FIGS. 10 (a) and 10 (b), when an obese worker M1 and a lean worker M2 stand at the same measurement position in the gate monitor, the obese worker M1 The distance d1 between the abdomen and the detectors 23 and 24 is significantly shorter than the distance d2 between the abdomen of the thin worker M2 and the detectors 23 and 24. Therefore, the detection efficiency of the abdomen of both workers does not match. In particular, when precision measurement is performed, the influence of fluctuations in the detection efficiency on the detection sensitivity near the detection limit becomes very large.

The present invention has been made in view of the above circumstances, and the detectors on the front and rear surfaces and the left and right side surfaces can be arranged close to the operator in accordance with the operator's body shape. It is an object of the present invention to provide a highly reliable body surface gate monitor which can always realize a constant detection efficiency regardless of the above, and which has no uneven detection sensitivity.

[0008]

The present invention has taken the following means in order to achieve the above object. The present invention corresponding to claim 1 has an entrance door and an exit door, and an examinee who is not contaminated by determining the presence or absence of contamination on the body surface of the examinee who entered the monitor main body from the entrance door In the body surface gate monitor for exiting from the exit door, the inner wall of the monitor main body is independently approached and retreated with respect to the region facing the front surface, rear surface or side surface of the subject. A group of freely arranged radiation detectors, a plurality of drive units for independently moving the radiation detectors toward and away from the subject, and detection of the radiation detectors provided in the radiation detectors A plurality of position detection sensors each detecting the body surface position of the subject corresponding to the range, and each radiation detection by controlling each drive unit based on each body surface position information detected by each position detection sensor In front of And a control means for stopping at a fixed distance from each body surface position of the object.

According to a second aspect of the present invention, in the body surface gate monitor having the above structure, between the feet of the subject, which is provided at the height of the foot of the subject and is upright in the monitor body. And a foot inner surface detector for detecting contamination of the foot inner surface inserted into the.

[0010]

The present invention has the following effects by taking the above measures. According to the present invention, which corresponds to claim 1, a plurality of radiation detectors independently approach and approach an inner wall of the monitor main body and face a front surface, a rear surface, or a side surface of the subject. It is arranged so that it can move backward. Before the inspection is started, each radiation detector independently approaches the subject by the drive unit, and the approaching operation is stopped based on each body surface position information detected by each position detection sensor. Therefore, the radiation detector can be stopped at a constant distance from each body surface position of the subject.

According to the second aspect of the present invention, since the foot inner surface detector can be inserted between the feet of the subject in the upright state in the monitor body, contamination of the foot inner surface can be prevented. Can be detected.

[0012]

Embodiments of the present invention will be described below. In this embodiment, the detectors 21 to 26 on the front and rear surfaces and the left and right side surfaces are used.
(Front surface detector), 31 to 36 (rear surface detector), 41 to 4
4 (left side detector), 51-54 (right side detector)
It is configured to be able to independently approach and retreat to the operator according to the body shape of the operator. Note that this embodiment has the same configuration as the body surface gate monitor of FIG. 9 described above, except for the configuration for approaching the respective detectors. FIG. 1 shows a state in which the front surface detectors 21 to 26 are moved close to the worker M so that the distance between the worker M and the detector is constant.

Here, the configuration of the drive unit and the control system (which exemplifies the detector 21) will be described by taking one detector in the front detector group as an example. FIG. 2 is a diagram showing a configuration of a drive unit and a control system regarding the detector 21. The detector 21 is supported via a plurality of support rods 62a and 62b on a detector mounting base 61 that is movably held in a horizontal direction (arrow A), which is a direction toward the worker, by a support structure (not shown). There is. Each of the support rods 62a and 62b has a tip end fixed to the detector 21, and a base end thereof slidable in a longitudinal direction (horizontal direction) in each through hole provided in the detector mounting base 61. Has been inserted. Springs 63a and 63b having the same length are wound around the outer peripheral surface of the support rod between the detector 21 and the detector mounting base 61. Both ends of the springs 63a and 63b are fixed to the detector 21 and the detector mounting base 61, respectively. Piezoelectric switches 64a to 64c as position detection sensors are attached to the radiation detection surface of the detector 21, that is, the surface facing the worker. The piezoelectric switches 64a to 64c can detect a pressure applied by contact with an object and output a detection signal.

FIG. 3 shows an arrangement example of the piezoelectric switches 64a to 64c. In this example, a plurality of piezoelectric switches 64 are provided on the center line of the radiation detection surface of the detector 21.
a to 64c are arranged, and the approach operation is stopped after a predetermined time has elapsed after any one of the piezoelectric switches outputs a detection signal.

The detector mounting base 61 has a longitudinal direction indicated by an arrow A.
One end of the rack 65 parallel to the direction is fixed. A pinion 66 is meshed with the rack 65, and the pinion 66 is configured to be rotationally driven by a flexible motor 67. The flexible motor 67 is connected to a power source via a contact 68. The control unit 69 switches the contact point 68 on and off and controls the rotation direction of the flexible motor 67 so as to control the approaching / retracting operation of the detector mounting base 61.

On the other hand, in the gate monitor of this embodiment, a detector for measuring the inner surface of the foot of the worker M (hereinafter referred to as "foot inner surface detector") is provided at the center of the foot measuring unit 26 in the front detector group. 70). FIG. 4 shows a conceptual diagram of the foot inner surface detector 70. Incidentally, reference numeral 71 in the figure is a photo mark. The foot inner surface detector 70 is composed of a plate-shaped member having a size (thickness, planar shape) that can be inserted between both feet of the worker M as shown in FIG. 4. A moving rail 71 is arranged on the foot measuring unit 26 along the arrow A direction. Further, on the end surface of the foot inner surface detector 70 on the foot measuring portion side, a moving guide 72 having a shape capable of moving on the moving rail 71.
Are integrally formed so as to project. Then, as shown in FIG. 6, the moving guide 72 of the foot inner surface detector 70 is placed on the moving rail 71 and moved. A plurality of photoelectric switches 73a, 7a for confirming the rear surface position of the foot are provided on the front surface in the traveling direction of the foot inner surface detector 70.
3b is provided. The photoelectric switches 73a and 73b are connected to the control system of the foot inner surface detector 70.

The foot measuring unit 26 is the detector 2 shown in FIG.
As in the case of 1, the foot inner surface detector 70 is configured so as to be able to perform a proximity operation independently of other detectors.
With the same configuration as that of 1, the foot measuring unit 26 is configured to be capable of a proximity operation independently. Further, the other detectors 22 to 25 in the front detector group and the other detectors are also the above-mentioned detector 2
As in the case of No. 1, each is configured to be able to operate independently.

FIG. 7 shows a structural example of the foot inner surface detector 70. As shown in the figure, when the foot inner surface detector 70 is inserted between both feet of the worker, plastic scintillators 74a and 74b are installed on both side surfaces facing the side surface of the foot, respectively.
A light guide 75 is provided between 74b. A photomultiplier tube 80 is provided on the end surface of the light guide 75.

The operation of the present embodiment configured as described above will be described with reference to FIG. In the gate monitor of the present embodiment, the operator M, who is the subject, enters the gate monitor and recognizes that the worker is at the measurement position by opening and closing the entrance door once, and the worker presses the hand switch of the hand measurement unit. By detecting the fact, the operator recognizes that the operator is ready to measure with both hands placed on the hand measurement unit. After confirming that the measurement is ready, the head detector accommodating portion 6 is lowered and the worker M
Stop at a certain position from your head. Next, the front detector group is moved closer. Further, the worker M confirms that the head detector accommodating portion 6 has stopped and presses the hand switch for operating the front detector group.

Here, the approaching movement of the front detector group will be described in detail by taking the detector 21 as an example. When the control unit 69 receives the approach start signal from the hand switch, it instructs the flexible motor 67 to rotate forward and closes the contact 68. As a result, the flexible motor 67 rotates in the forward direction, and the rotational force is transmitted to the detector mounting base 61 via the rack and pinion mechanism as a force that horizontally moves to the operator side in the direction of arrow A. When the detector mounting base 61 moves, the support rods 62a and 62b supported by the detector mounting base 61 and the detector 21 attached to the tips of the support rods 62a and 62b.
Work together and approach the same distance at the same time. When the radiation detection surface of the detector 21 touches the body surface of the worker M, substantially simultaneously with that, one of the piezoelectric switches 64a to 64c contacts the body surface of the worker M and outputs a detection signal to the control unit 69. To do. Upon receiving the detection signal, the control unit 69 commands the flexible motor 67 of the detector 21 to rotate in the reverse direction, starts counting time with a timer, and when a predetermined time elapses, the control unit 69 opens the contact point 68 on the power supply line. Open up. As a result, the detector 21 stops at a predetermined distance from the body surface of the worker M.

The detector 21 moves forward from the time the detector 21 touches the worker M until the flexible motor 67 reversely rotates and starts to move backward. However, since the support rods 62a and 62b supporting the detector 21 are inserted through the detector mounting base 61, the worker M receives the spring 63.
Only the drag forces of a and 63b act, and the pressing force applied to the worker M can be made so small that it does not matter. Also, the detector 2
If the movement stroke of 1 is shorter than the buffer distance by the springs 63a and 63b, there is no safety problem.

Since the other detectors on the front and rear surfaces and the left and right side surfaces also perform the same operation as the detector 21, the other detectors also stop at the same distance as the detector 21 from the body surface of the worker M. To do.

The foot inner surface detector 70 is horizontally moved so as to be inserted between both feet of the worker M as shown in FIG. 4, and the end portion of the foot inner surface detector 70 in the traveling direction is the worker. The movement is stopped when the photoelectric switches 73a and 73b detect that the foot of M has come to the rear side.

Measurement is started after the approaching operation of all the detectors is completed as described above. For example, in the case of the foot inner surface detector 70, when radiation is emitted from a radiation source attached to the clothes of the worker M and enters the plastic scintillator 74a, that portion emits light. The light enters the photomultiplier tube 80 via the light guide 75, where it is amplified and extracted as an electric signal. This electric signal is sent to the processing system as a radiation detection signal.

The measurement time of the timer is monitored, and the measurement is finished when a predetermined time has elapsed from the start of the measurement. The radiation detection signal of each detector is sequentially transmitted to a processing system (not shown), and the contamination density of each part is calculated there. As a result of this calculation, when the contamination density is equal to or less than the specified value, "no contamination" is displayed in a place where the operator M can visually confirm, and the exit side door is opened. However, if the pollution density is higher than the specified value, "contaminated"
Is displayed, the exit side door remains locked and the entrance side door is opened. After decontamination, they will be inspected again.

As described above, according to this embodiment, the detectors 21 to 26 (front face detectors) 31 to 31 on the front and rear surfaces and the left and right side surfaces are formed.
36 (rear surface detector), 41 to 44 (left side surface detector), 5
1 to 54 (right side surface detector) are configured so that they can independently approach and approach the worker according to the body type of the worker. The distance between them can always be set to a constant distance, and the detection efficiency can be kept constant. Therefore, the detection sensitivity is constant for any worker, and highly reliable contamination measurement can be performed.

According to this embodiment, since the foot inner surface detector 70 is inserted between the both feet of the worker, it is possible to inspect the inner surface of the foot which has not been measured conventionally. Since the radiation to be measured in this embodiment is mainly β rays, the thickness of the plastic scintillators 74a and 74b which are the constituent elements of the foot inner surface detector 70 is set to 0.1 m.
It is possible to make the detector as thin as about m, and it is possible to create a detector having dimensions that do not hinder measurement.

Although the piezoelectric switch is used to detect the body surface of the worker M in the above description, other position detection sensors, such as a proximity switch, may be used. The present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the present invention.

[0029]

As described in detail above, according to the present invention, the detectors on the front and rear surfaces and the left and right side surfaces can be arranged close to the operator in accordance with the operator's body shape, regardless of the operator's body shape. A constant detection efficiency can always be realized, and a highly reliable body surface gate monitor without uneven detection sensitivity can be provided.

[Brief description of drawings]

FIG. 1 is an operation conceptual diagram of a body surface gate monitor according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a drive unit and a control unit of a detector in the body surface gate monitor according to the embodiment.

FIG. 3 is a plan view showing an arrangement example of piezoelectric switches provided on a detector surface.

FIG. 4 is a schematic view of a foot inner surface detector.

5A and 5B are a top view and a side view of a foot measurement unit and a foot inner surface detector.

6 is a cross-sectional view taken along the line BB shown in FIG.

FIG. 7 is a configuration diagram of a foot inner surface detector.

FIG. 8 is a flowchart showing the operation of the body surface gate monitor according to the embodiment.

FIG. 9 is a view of a general body surface gate monitor as viewed from the side, front, and top.

FIG. 10 is a diagram showing a relationship between an operator's body surface and a detector in a conventional body surface gate monitor.

[Explanation of symbols]

2 ... Front detector accommodating portion, 3 ... Rear surface detector accommodating portion, 4, 5
... Side detector accommodating portion, 6 ... Head detector accommodating portion, 7 ... Foot detector accommodating portion, 21-26, 31-36, 41-44,
51-54, 71-72 ... Radiation detector, 61 ... Detector mounting base, 62a, 62b ... Support rods, 63a, 63b ...
Spring, 64a-64c ... Piezoelectric switch.

Claims (2)

[Claims] 1. An entrance door and an exit door are provided, and the presence or absence of contamination on the body surface of the examinee who enters the monitor main body from the entrance door is judged to determine the uncontaminated examinee from the exit door. In the body surface gate monitor to be withdrawn, the inner surface of the monitor main body is arranged in an area facing the front surface, the rear surface, or the side surface of the subject so that the subject can independently approach and retract. A group of radiation detectors, a plurality of drive units that independently move the radiation detectors toward and away from the subject, and an object that corresponds to the detection range of each radiation detector that is provided in each of the radiation detectors. A plurality of position detection sensors for respectively detecting the body surface position of the specimen, and the radiation detectors for the subject by controlling the respective drive units based on the body surface position information detected by the respective position detection sensors. Each of Body surface gate monitor, characterized by comprising a control means for stopping the surface position at a certain distance, a. 2. The body surface gate monitor according to claim 1, wherein a foot portion provided at the height of the foot portion of the subject and inserted between both legs of the subject standing upright in the monitor body. A body surface gate monitor comprising a foot inner surface detector for detecting contamination on the inner surface.