JP3138431B2 - Body surface monitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a body surface monitor for measuring radiation from a radioactive substance attached to the body of a subject.

[0002]

2. Description of the Related Art In a radiation handling facility such as a nuclear power plant and a nuclear fuel processing facility, a body surface monitor is used.
The body surface monitor is provided at an exit of a radiation management area or the like for inspecting the presence or absence of a radioactive substance attached to the body surface of the worker. Before lunch or after the work is completed, many workers pass through the body surface monitor, so that a row of workers often forms before the body surface monitor.

A conventional general body surface monitor has a measurement room as a box for accommodating a subject. The measuring chamber has an entrance door and an exit door. Further, a plurality of radiation detectors are provided in the measurement room toward the subject inside.
For example, a front detector that detects radiation from the front of the subject, a side detector that detects radiation from the side of the subject, and a back that detects radiation from the back of the subject A detector, a head detector that detects radiation from the subject's head, a hand detector that detects radiation from the subject's hand, and the like are provided. Each detector is composed of, for example, a scintillator detector.

Here, the head detector is moved up and down by an elevating mechanism according to the height of the subject. The lifting mechanism is provided with a sensor that detects that the head detector has approached the head of the subject, and when a detection signal is output from the sensor, the lowering of the head detector by the lifting mechanism is stopped, In that state, radiation measurement is performed for a predetermined time. The hand detector is fixed to the measurement chamber, and the radiation from the hand is measured by inserting the hand into the receiving groove. Further, a display is fixedly provided in the measurement room in order to give necessary instructions and information to the subject.

It should be noted that JP-A-4-310892, JP-A-2-264882, and JP-A-2-112787.
Gazette, Japanese Unexamined Patent Publication No. 6-258442,
No. 8387 discloses a conventional body surface monitor.

[0006]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Laid-Open No. 4-310 is disclosed.
In Japanese Patent No. 892, a light beam switch for determining a height division is provided, and the standby position of the head detector is corrected according to the height division. However, since the height of the light switch is fixed, there is a problem that the definition of the height division cannot be freely changed, in other words, the initial standby position cannot be changed. Although it is possible to make the height division finer, in that case, a plurality of light switches are required, and as a result, there has been a problem that the apparatus cost is increased.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has as its object to determine, from the relationship with a standby position of a head detector, whether or not the height is acceptable at the standby position. The object of the present invention is to allow a body surface monitor having a function to perform a change of a waiting position to automatically change a criterion of acceptability.

[0008]

In order to achieve the above object, the present invention provides a measuring chamber for accommodating a subject and a means for detecting radiation from the head of the subject, comprising: A head detector for which a provisional standby position is set at a height lower than a predetermined distance from an upper limit, and after receiving the subject in the measurement room, lowering the head detector to obtain the subject An elevating mechanism for positioning the head detector on the head of the head, and ascending and descending integrally with the head detector, for comparing the upper limit of acceptance with the height of the subject based on the standby position Comparative measurement means for performing comparative measurement, and a control unit that controls the elevating mechanism based on the result of the comparative measurement, including, the control unit compares the acceptance upper limit and the height of the subject,
When the height is higher than the acceptance upper limit, control is performed to pull the head detector upward from the standby position.

According to the above configuration, the height measured by the comparison measuring means is adjusted in accordance with the height of the head detector, that is, if the head detector is positioned at a standby position of any height, An appropriate height of the comparative measurement point can be automatically set by the positioning. Therefore, there is an advantage that it is not necessary to separately control the height of the measurement point of the comparison measurement means.

[0010] In a preferred aspect of the present invention, the comparative measurement means includes an object at a height corresponding to the acceptance upper limit above a waiting place of a next subject set before the entrance of the measurement chamber. Sensor for detecting the presence or absence of

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a preferred embodiment of a body surface monitor according to the present invention, and FIG. 1 is a view showing the overall configuration. The body surface monitor 10 is provided at an exit of a radiation control area in a facility such as a nuclear power plant.
Or a plurality of units are installed.

A measurement room 12 for accommodating a subject 8 is formed inside the body surface monitor 10. The subject 8 enters the measurement room 12 via the entrance door 14. In this state, measurement of radiation from the body surface is performed for a predetermined time, and after the measurement is completed, the subject 8 goes out through the exit door 16. FIG. 1 shows a subject waiting place 106 where the subject 8 to be measured next stops. The subject waiting place is set by, for example, marking a mark on the floor.

A plurality of radiation detectors are arranged so as to surround the measurement chamber 12. Head detection unit 18
Is a unit for detecting radiation from the head of the subject 8, and the head detection unit 18 is supported so as to be able to move up and down as in the conventional example. A detector 34 for detecting the radiation from the right side of the subject is provided in the entrance door 14, while the exit door 16 is for measuring the radiation from the left side of the subject 8. Is provided.
As shown in FIG. 2, a detector 39 is arranged on the front side of the subject 8, while the detector 4 is located on the back side of the subject 8.
5 are arranged. These detectors detect radiation by a scintillator made of plastic, and details thereof will be described later.

In FIG. 1, a hand detection unit 2 for detecting radiation from both hands of a subject 8 is provided on a body surface monitor 10.
2A and 22B are provided. Each of these hand detection units 22A and 22B is supported so as to be able to move up and down similarly to the head detection unit 18.

Each detector will be described in detail. The head detection unit 18 is provided with a plate-shaped scintillator 26. A pair or a plurality of pairs of photomultiplier tubes 28 are provided on both sides of the scintillator 26. Scintillator 26
The head detector 25 is constituted by the plurality of photomultiplier tubes 28. The head detecting unit 18 has a recess for accommodating the head of the subject 8, and a scintillator 26 is arranged on the ceiling of the recess. A light emitting device 31 and a light receiving device 32 are provided near the edge of the recess, and these constitute a head sensor 30. The head sensor 30 is a sensor for detecting that the head of the subject 8 has entered the hollow when the head detection unit 18 is lowered, and as described later, the head detection unit The descent of 18 stops immediately.

A display 20 is attached to the head detection unit 18 via an arm 19. This display 20
Is composed of, for example, a liquid crystal display, and is for issuing a notice or an instruction to the subject 8 during or before or after the measurement. For example, a message such as “Measurement is being performed” is displayed on the display 20. In the present embodiment, the display 20 moves up and down integrally with the head detection unit 18. When the head detection unit 18 is properly positioned on the head of the subject 8, the display 20 is positioned at the height of the face of the subject 8. Display 2
Numeral 0 is provided in an oblique direction shifted leftward from the front side of the subject 8, and a certain distance is secured between the subject 8 and the display 20. In the present embodiment, the display 20 has the screen of the subject 8 accommodated in the measurement room 12.
Although it is set obliquely so as to face vertically, a mechanism for controlling the direction and angle of the display 20 may be provided.
A mechanism for adjusting the distance between the head detection unit 18 and the display 20 according to the height of the head detection unit 18 may be provided.

In this embodiment, the head detecting unit 1
The highest height 8, that is, the origin, is set to, for example, 2 meters from the floor 11 of the measurement room 12. The minimum height of the head detection unit 18 is set to, for example, 135 cm in order to accommodate elementary school students and the like. Of course, such upper and lower limits can be changed as appropriate.

As shown in FIG. 1, the two hand detecting units 22A and 22B are respectively
It descends in conjunction with the fall of. For example, in the present embodiment, when the head detection unit 18 is lowered by 20 cm, the hand detection units 22A and 22B are controlled to be lowered by 10 cm. As will be described later, these units are controlled to move up and down by a single driving mechanism, thereby simplifying the mechanism of the apparatus.

The hand detection units 22A and 22B are formed with vertical groove-shaped insertion portions 23A and 23B for inserting hands. In this embodiment, a hand detecting unit of a type in which the palm is inserted into the insertion portions 23A and 23B while the palm is in a vertical state is used. However, a hand detecting unit of a type in which the palm is inserted horizontally is also used. Good.

The body surface monitor 10 of this embodiment is provided with a sensor 100 for measuring the presence or absence of an object in the head detection unit 18. This sensor 100 is an optical sensor or an ultrasonic sensor. The sensor beam (light beam or ultrasonic beam) 200 is directed above the next subject's waiting location 106, specifically, the beam is directed above the waiting location and is currently At the standby position of the head detection unit 18 of the head, the height is set so as to intersect the height corresponding to the upper limit (acceptable height) of the height that can be accepted. The floor 11 of the measurement room 12 of the body surface monitor 10 is raised by a predetermined amount (h1) above the floor surface on which the standby place 106 is located, and the standby position is set to be higher than the reception upper limit by a predetermined amount (h2). Therefore, the beam 200 is directed downward by an amount corresponding to the sum. That is, the beam is set slightly downward so as to pass over a point corresponding to the height that can be accepted at the current standby position of the head detector above the standby position 106 on the floor. Of course, the beam angle depends on the position of the sensor 100 in the head detection unit 18.

Therefore, when the head of the next subject crosses the beam 200, the standby position of the head detecting unit 18 is found to be too low to accept the next subject. In this case, control is performed to retract the head detection unit 18 upward by a certain amount or to the origin. Of course, if the beam 200 does not cross the next subject's head, the subject is accepted as is.

According to the above configuration, a mechanism for raising and lowering the sensor 100 in accordance with the standby position is not required, and the beam 200 can be translated in parallel with the raising and lowering of the head detecting unit 18. That is, the head detection unit 18
The beam height can be set at the same time as the positioning. In addition,
In the case where the beam 200 is blocked by the entrance door 14, the measurement by the sensor 100 may be performed when the entrance door 14 is opened. Alternatively, the sensor 100 may be provided at a position not concealed by the entrance door 14 or the like. In any case, it is desirable to control the position of the sensor 100 or the beam 200 using the elevation of the head detection unit 18.

The beam 200 is used to increase the reliability of the measurement.
May be scanned in the horizontal direction. Alternatively, as shown in FIG. 8, the presence or absence of an object may be determined based on the sensor output only during a certain gate period. FIG. 8A shows the sensor output, and FIG. 8B shows the gate signal. Only during the ON period of the gate signal, the sensor output is compared with the threshold value 202, and the sensor output is
If it exceeds 2, the presence of the object is determined. That is,
It is determined that the height is higher than the acceptable height. Needless to say, the gate period is set to a time corresponding to the position of the standby place 106. The discrimination accuracy may be increased by using other methods.

FIG. 2 shows a specific configuration of each detector. In the present embodiment, the detector 39 on the front side is 3
The back side detector 45 includes three scintillators 46, 48, 50.
including. Further, the detector 36 built in the exit door is 3
And two scintillators 52, 54, 56. This is the same for the entrance door 14. FIG. 2 shows a state where the head detection unit 18 is positioned on the head of the subject 8. In this state, the display 20 is positioned at the height of the face of the subject 8.

FIG. 3 is a diagram showing a state where the body surface monitor 10 is viewed from above. The entrance door 14 is the next subject 8
The rotating shaft is on the right side when viewed from the side, and is configured to open toward the front. The exit door 16 has a rotation axis on the left side when viewed from the measurement chamber 12 side, and is configured to open outward. This is similar to a conventional body surface monitor.

Each hand detection unit 22A, 22B has a pair of scintillators 58, 60, 62, 64, respectively. Insertion parts 23A, 23B between those scintillators
Is formed. As described above, the display 20 is connected to the measurement chamber 12.
Is positioned diagonally forward left of the subject.
When the display 20 is lowered, the hand detection unit 22 is also lowered at the same time, so that the two do not collide.

FIG. 4 shows a specific example of the lifting mechanism 112. The elevating mechanism 112 includes the head detecting unit 18.
And functions as an elevator mechanism for raising and lowering the two hand detection units 22. A pair of rails 72 are provided on the substrate 70 along the vertical direction. A feed screw 76 is provided between the rails 72, and the feed screw 76 is driven to rotate by a motor 74. The head detecting unit 18 is supported by a rail 72 so as to be vertically movable, and the rotation of the feed screw 76 is converted into a vertical movement of the head detecting unit 18 via a screw receiver 79. At the upper end of the feed screw 76, an encoder 82 for detecting the amount of rotation, that is, the height of the head detecting unit 18 and the hand detecting unit 22 is provided. In the head detecting unit 18, an L-shaped angle 80 is connected to a leg 78 extending over the rail 72, and the head detector 25 is fixed to the L-shaped angle 80. Although not shown in FIG. 4, the display 20 is also fixed to the L-shaped angle 80.

The two hand detection units 22 are provided on the rail 7
2, and the two hand detection units 22 are driven by wires 84 in the vertical direction. One end of the wire 84 is fixed to an L-shaped angle 80 in the head detection unit 18,
Is fixed to the substrate 70. Each hand detection unit 22 is provided with a rotatable pulley 86, and a wire 84 is wound around the pulley 86. Therefore, when the head detecting unit 18 moves downward, the hand detecting unit 22 moves downward by half of the amount of the downward movement. Empirically, if the hand detection unit 22 is lowered by half the amount of the head detection unit 18 being lowered, the hand detection unit 22 can be appropriately positioned with respect to the subject. Therefore, in a state where the head detection unit 18 is positioned at the highest position, the length of the wire 84 is adjusted so that the hand detection unit 22 matches the position of the hand of the subject having the height corresponding to the height. Is set.

Therefore, when the subject enters the measuring chamber 12, the head detecting unit 18 is lowered from above by the action of the motor 74. Head sensor 30 shown in FIG.
When the head is detected, the descent of the head detection unit 18 is stopped at that time. In a state where the hand detection unit 22 is also lowered in conjunction with the lowering of the head detection unit 18 and the head detection unit 18 is appropriately positioned on the head,
The hand detection unit 22 is also appropriately positioned at the height of the hand. Of course, the display 20 driven integrally with the head detection unit 18 is also appropriately positioned according to the height of the subject.

According to the above-described configuration, the three devices including the head detection unit 18 (including the sensor 100 for determining acceptability), the hand detection unit 22 and the display are moved up and down by a single drive source. This has the advantage that the configuration of the device can be simplified. FIG. 5 shows a state where each component is positioned according to the height of the subject. According to the body surface monitor of the present embodiment, there is an advantage that radiation from the body surface can be detected over a wide range from a tall subject to a small subject such as an elementary school student without any problem.

The elevating mechanism 112 shown in FIG. 4 is not limited to the one shown in the figure, but may employ another structure. For example, when raising and lowering the hand detection unit 22, the wire 8
A gear or the like may be used without using the fourth gear.

FIG. 6 is a block diagram showing the functions of the body surface monitor. The control unit 110 is composed of, for example, a microcomputer or the like.
Have a plurality of detectors 22, 25, 34, 36, 39, 45
Is connected. The detection signals from these detectors are sent to the control unit 110, and the area density of the radiation and the like are calculated. The control unit 110 is connected to a head sensor 30 for detecting the height of the head, an elevating mechanism 112, and a sensor 100 for determining whether or not the head can be accepted.
14 are connected.

FIG. 7 is a flowchart showing the control by the control unit 110. The operation of the body surface monitor of the present embodiment will be described with reference to FIG.

In a state where the head detecting unit 18 is positioned at the set standby position, the entrance door 14 is opened in S101, and in S102, the subject 100 receives the subject prior to entering the measuring chamber 12. Measurement is performed for the determination of availability. The acceptance upper limit is determined, for example, as a height obtained by adding a predetermined margin (for example, 10 cm) to the standby position.

In S103, it is determined whether the height of the subject is less than or equal to the upper limit of acceptance. If it is equal to or lower than the upper limit, S105 is executed. If it is equal to or higher than the upper limit, control is performed to retract the head detection unit 18 to the upper origin in S104.

In S105, when it is detected that the subject has entered the measuring chamber 12, control is started in S106 to lower the head detecting unit 18 from above to below at a low speed. The lowering is performed until the head is detected by the head sensor 30 in S107. With such control, high-precision measurement can be performed by bringing the head detection unit 18 close to the subject's head. When the head is detected by the head sensor 30, the descent is immediately stopped in S108. In S109, the height data of the subject determined by such positioning on the head is stored in the storage unit 114 shown in FIG. The height of the subject is determined based on the descent stop position of the head detection unit 18 detected by the encoder 82. When storing height data, if the subject is identified,
Height data is stored in association with the identification information. In S110, detection of radiation from the body surface is continuously performed for a predetermined time (for example, ten and several seconds).

In step S111, a predetermined amount α is added to the height of the subject.
(For example, 10 cm), the head detection unit 18 is raised at a high speed to the height added. α is appropriately set according to, for example, the depth of the depression of the head detection unit 18.

In S112, the exit door 16 is opened,
When it is confirmed that the subject has come out, the head detection unit is positioned at a predetermined standby position at a high speed in S114. Then, the exit door 16 is closed in S115.

In the above control, when positioning the head detecting unit 18 with respect to the subject 8, the subject 8
In this case, low-speed control is performed in consideration of a psychological sense of oppression and malfunction of the apparatus. In other cases, high-speed movement control is performed on the head detection unit 18 in order to shorten the measurement time. Further, instead of lowering the head detection unit 18 from the origin after the subject 8 enters the measurement room 12, the head detection unit 18 is previously set at a predetermined standby position corresponding to the height of the subject 8. Since it is lowered after positioning, there is an advantage that the time required for the descent can be reduced and the measurement time as a whole can be reduced. Of course, when the height of the subject is higher than the acceptance upper limit determined from the standby position, it is determined using the sensor 100,
Since the head detecting unit is pulled up, there is no possibility that the head detecting unit 18 collides with the head of the subject.

[0041]

As described above, according to the present invention,
It is possible to provide a body surface monitor having a function of determining whether or not the height is acceptable at the standby position based on the relationship with the standby position of the head detector. It is possible to automatically change the criterion of the availability.

[Brief description of the drawings]

FIG. 1 is a diagram showing an entire configuration of a body surface monitor according to the present invention.

FIG. 2 is a diagram showing a specific configuration of each detector.

FIG. 3 is a top view of the body surface monitor.

FIG. 4 is a diagram showing a specific configuration of a lifting mechanism.

FIG. 5 is a diagram showing positioning of each component corresponding to each height.

FIG. 6 is a block diagram illustrating functions of a body surface monitor.

FIG. 7 is a flowchart showing the operation of the body surface monitor.

FIG. 8 is a diagram showing a relationship between an output signal of a sensor and a gate signal.

[Explanation of symbols]

12 measurement room, 14 entrance door, 16 exit door, 18 head detection unit, 20 display, 22 hand detection unit, 25 head detector, 34, 36 detector, 82 encoder, 100 sensor, 112 lifting mechanism.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01T 1/169

Claims (2)

(57) [Claims] 1. A measurement chamber for accommodating a subject, and means for detecting radiation from the subject's head, wherein a temporary standby position is set at a height lower than a predetermined distance from an upper limit of a lifting path. After receiving the subject in the measurement room, the head detector is lowered, the lifting mechanism for lowering the head detector and positioning the head detector on the head of the subject, A comparison measurement unit that moves up and down integrally with the head detector and performs a comparison measurement for comparing the upper limit of acceptance based on the standby position and the height of the subject, based on a result of the comparison measurement. A control unit that controls the elevating mechanism, wherein the control unit compares the height of the subject with the upper limit of acceptance, and when the height is higher than the upper limit of acceptance, the head detector The body is controlled to be pulled upward from the standby position. Surface monitoring. 2. The body surface monitor according to claim 1, wherein the comparison measuring unit detects the presence or absence of an object at a height above the next subject's waiting place and at a height corresponding to the acceptance upper limit. A body surface monitor, characterized in that: