JP2014163695A - Monitoring cart - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a monitoring cart capable of sensitively detecting radiation from a contamination source even when it approaches the contamination source to some extent, and to allow the detection limit angle to smoothly vary depending on the azimuth.SOLUTION: The front surface 18b of a housing 18 constitutes a semi-cylindrical surface. Thus, the front edge of the top surface 18a constitutes a semicircle. A scintillator member is disposed inside a detection section 20. The front edge is curved so as to surround the scintillator member in the view from the scintillator member, so that the azimuth dependence of the detection limit angle for radiation coming from the downside can be made low, or the detection limit angle can be smoothly varied depending on the azimuth.

Description

  The present invention relates to a monitoring cart, and more particularly to a monitoring cart used in searching for a radioactive contamination source (hot spot).

  In order to effectively remove and reduce contamination (decontamination work) in a radioactively contaminated area, it is desirable to identify a place (hot spot) where the concentration of radioactive material (eg Cs-137) is higher. It is. After identifying the hot spot, an operation of removing soil or the like from the place or cleaning the place is performed.

  A general survey meter is basically omnidirectional. If it is near the hot spot, it is possible to identify the hot spot (especially a local contaminated site) from the dose change accompanying the observation of the survey meter. However, it is very difficult to specify a hot spot using a survey meter for a wide area.

  Therefore, it is desirable to use a radiation measurement apparatus that can specify the radiation direction when specifying the hot spot. For example, Patent Document 1 discloses an apparatus that identifies the radiation direction of radiation from the mutual ratio of a plurality of count values obtained using a plurality of scintillators. In addition, an apparatus for specifying a flying direction using a shield that is rotationally driven has been proposed (Patent Document 2). Several other devices have been proposed (Patent Documents 3, 4, 5, and 6). Note that Japanese Patent Application No. 2012-078776 is an unpublished prior application related to the present application.

JP 2007-155332 A JP 2004-325417 A JP 2008-134200 A JP 2004-301798 A JP 2004-170125 A JP 2004-20431 A

  In order to specify a hot spot, it is desired to measure the flying direction at a plurality of points while moving. However, when a measuring device is mounted on a large vehicle such as an automobile, the entire facility is enlarged and the mobility is impaired. There is a need for a device that can move easily through narrow spaces and narrow passages.

  If it is assumed that the measurement is performed while maintaining the radiation detector at a certain height from the ground surface, the radiation coming from the horizontal direction is measured when the contamination source is quite far away. In that case, it is desirable to configure so that radiation from directly below or obliquely below is not detected so much. On the other hand, when approaching the contamination source, for example, about several meters to several tens of meters, it is also necessary to measure radiation coming from obliquely below in order to identify the contamination source. In addition, in order to specify the radiation azimuth with high accuracy, the sensitivity characteristics (horizontal sensitivity characteristics and It is desirable that the vertical sensitivity characteristic is not disturbed. This is because if the detection sensitivity greatly changes or changes irregularly depending on the azimuth and the elevation angle, the reliability for specifying the azimuth is lowered.

  An object of the present invention is to realize a monitoring cart having mobility. Alternatively, it is an object of the present invention to be able to detect radiation from a contamination source even if it is close to the contamination source to some extent. Alternatively, an object of the present invention is to prevent the detection limit angle when detecting radiation from below from being greatly disturbed by the azimuth within a certain azimuth range.

  A monitoring cart according to the present invention includes a base unit having a plurality of wheels, a housing provided on the base unit, a handle member gripped by an operator standing on the rear side of the housing, and left and right surfaces on the upper surface of the housing. A detection unit including a radiation detector installed at a central position in the direction and higher than the upper surface level of the housing, and an orientation for specifying a radiation azimuth as a horizontal direction based on an output signal of the detection unit The housing has a front surface having a semi-cylindrical shape that swells forward, and a front edge of the upper surface of the housing is curved in an arc around the detection portion. Features.

  According to the above configuration, a mobile monitoring cart can be configured. The monitoring cart is preferably like a wheelbarrow, which is basically not a moving body on which a human is placed, but is moved by the power of an operator (measurer). However, a power source may be mounted on the monitoring cart in order to reduce or eliminate the burden on the operator.

  The housing constitutes a housing, which is made of, for example, metal. Such a material has a radiation shielding effect or radiation attenuation effect to a greater or lesser extent. A measurement circuit, an arithmetic circuit, and the like are arranged in the housing. The front surface of the housing bulges forward and has a semi-cylindrical shape. The curvature is preferably constant regardless of the direction, but may be continuously changed depending on the direction. The front edge of the upper surface is curved around the detection unit, and its form is an arc. Here, the front edge corresponds to a boundary line connecting the upper surface and the front surface. Since the front edge provided so as to surround the detection unit as viewed from above has an arcuate shape, the detection limit angle in the radiation detector does not change depending on the direction or changes smoothly even if it changes. Here, the detection limit angle is the maximum value of the negative angle at which radiation detection can be performed without being blocked by the housing when the horizontal direction is defined as 0 degree and the angle below the horizontal direction is defined as a negative angle. . That is, according to the above configuration, the radiation coming from diagonally below can be positively detected over a certain forward azimuth range, so the flying azimuth can be determined even when approaching the contamination source. Further, the azimuth dependence of the vertical sensitivity characteristic (or vertical directivity characteristic) can be reduced over a certain forward azimuth range. Therefore, the direction specifying accuracy can be increased.

  Preferably, the upper surface of the housing has a semicircular front region and a rear region connected to the semicircular region, and the detection unit is installed in the front region. According to this configuration, the detection unit is installed in the front region on the upper surface of the housing, and the influence of the operator existing behind (for example, the influence of scattered radiation generated in the human body) can be reduced. Since the detection unit exists in the visual field of the operator and the flying direction is determined based on the detection unit, it is easy for the operator to intuitively understand the flying direction.

  Preferably, the radiation detector is a scintillator member, and the detection unit includes a dome-shaped cover that accommodates the scintillator member. It is desirable to configure the detection unit so that the orientation can be determined.

  Preferably, the base unit includes a base plate having a radiation shielding function or an attenuation function, and the base plate extends forward from the front surface. According to this configuration, it is possible to shield or attenuate radiation that comes from directly below or in the vicinity thereof, so that background noise can be reduced. When the detection unit is arranged in the front region on the upper surface, it is desirable that the base plate spreads further forward than the front surface in order to effectively reduce the background noise entering there.

  Preferably, an azimuth indicator that is referred to when specifying the incoming direction of radiation is provided on the upper surface of the housing. According to this configuration, when the flying direction is specified, it is possible to easily recognize which direction is actually the flying direction. Preferably, the direction indicator is an annular scale provided around the detection unit. Since the detection unit is the detection origin, it is desirable to provide a scale indicating the flying direction with reference to the detection origin. According to this configuration, it is possible to recognize the flying direction more accurately even when the contamination source is close.

  According to the present invention, a monitoring cart having mobility can be realized. Alternatively, the radiation from the contamination source can be detected even if the contamination source is approached to some extent. Alternatively, the detection limit angle when detecting radiation from obliquely below can be prevented from being greatly disturbed by the azimuth within a certain azimuth range.

It is a perspective view which shows suitable embodiment of the monitoring cart which concerns on this invention. It is a side view of the monitoring cart shown in FIG. It is a rear view of the monitoring cart shown in FIG. It is a top view of the monitoring cart shown in FIG. It is a figure for demonstrating the detection limit angle which changes according to an azimuth | direction. It is a figure for demonstrating a comparative example. It is a block diagram of the monitoring cart shown in FIG.

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

  FIG. 1 shows a preferred embodiment of a monitoring cart according to the present invention, and FIG. 1 is a perspective view thereof. This monitoring cart is a device for searching for a local contamination source, that is, a hot spot, and in particular, can identify the direction in which the contamination source exists. The monitoring cart is moved by an operator, that is, a measurer, which is basically used outdoors, but may be used indoors.

  In FIG. 1, the monitoring cart 10 has a base unit 11. The base unit 11 includes a base plate 12 and a plurality of casters 14 and 16. The base plate 12 is made of, for example, a metal such as stainless steel, and is a plate-like member extending in the horizontal direction. The base plate 12 exhibits an action of shielding or attenuating γ rays as radiation. Incidentally, in FIG. 1, the X direction is the front-rear direction, the Y direction is the left-right direction, and the Z direction is the vertical direction. An operator is located behind the monitoring cart 10, that is, on the back side, and the monitoring cart 10 is moved and operated by the operator.

  As shown in FIG. 1, a pair of front casters 14 and a pair of rear casters 16 are provided below the base plate 12. Of these, for example, the front caster 14 is a pivotable caster. Of course, the rear caster 16 can also be configured as a pivotable caster. A brake mechanism may be provided for a plurality of casters 14 and 16 or a part of casters 14 and 16. It is also possible to mount an auxiliary power source and rotate the caster by the power source.

  A housing 18 as a housing is provided on the base unit 11. The housing 18 is made of a member such as aluminum, which corresponds to a hollow case. The cart body is configured as a whole including the housing 18 and the internal configuration. As shown in the figure, the housing 18 has an approximately box shape, but its front surface 18b swells forward and forms a semi-cylindrical surface. The curvature of the front surface 18b is the same over a range of 180 degrees, but of course, the curvature may be changed smoothly. A left side surface 18c is provided continuously to the front surface 18b, and a right side surface exists on the opposite side. A door is provided on the rear side of the housing 18. This will be described later with reference to FIG. The upper surface 18a of the housing 18 forms a flat horizontal plane. The upper surface 18a is composed of a semicircular front area and a rectangular rear area continuous therewith.

  A detection unit 20 is provided on the front area. As will be described later, the detection unit 20 includes a scintillator member and a dome-shaped cover 20A that accommodates the scintillator member. The scintillator member is entirely set at a position higher than the level of the upper surface 18a. A ring-shaped member is provided around the cover 20 </ b> A and functions as the orientation indicator 24. That is, the direction indicator 24 is configured as a scale representing each direction. For example, the flying direction may be displayed using an LED array or a liquid crystal display.

  A detection unit 20 is provided on the front side of the center of the upper surface 18a in the left-right direction, and an indicator lamp 22 is disposed in the center in the front-rear direction. This indicator light 22 is turned on when, for example, a contamination source is specified, that is, when a certain dose rate is measured. The display mode may be changed according to the dose rate.

  A left frame 26 is provided on the left side of the housing 18, and a right frame 28 is provided on the right side of the housing 18. These frames 26 and 28 have a symmetrical configuration. Therefore, the left frame 26 will be described as a representative. The left frame 26 has a pipe 30 arranged vertically and a pipe 32 arranged obliquely. The pipes 30 and 32 are connected at a joint portion 34. The upper end portion of the pipe 32 is bent, and the end portion as the bent portion constitutes the handle 36. That is, a right handle is provided on the right side of the housing 18 and a left handle is provided on the left side thereof. Two handles are gripped by the operator using both hands, and the monitoring cart 10 moves forward by pushing them forward. In addition, the monitoring cart 10 can be advanced in a desired direction by changing how the force is applied to each handle.

  As described above, the housing 18 is made of a metal member in the present embodiment, and exhibits a certain radiation attenuation effect. As will be described later, a photomultiplier tube, a central processing unit, a control unit, and the like are provided inside the housing 18, and a battery and the like are further provided. The housing 18 exhibits a shielding action, and the electronic circuit therein is protected from external electromagnetic waves.

  FIG. 2 shows a side view of the monitoring cart 10 shown in FIG. As described above, the base plate 12 exhibits the function of shielding the radiation 100C flying from directly below or near the bottom. In the housing 18, the front surface 18b constitutes a semi-cylindrical surface. A detection unit 20, an indicator lamp 22, and a stand jig 42 are provided on the upper surface 18a. The detection unit 20 includes a scintillator member 38 therein, and the scintillator member 38 is covered with a cover 20A.

  As shown in FIG. 2, the scintillator member 38 is provided at a position higher than the upper surface 18a. In order to indicate the center position of the scintillator member 18 in the vertical direction, a belt-like mark 40 is provided on the outer peripheral surface of the cover 20A. The stand jig 42 is used when a calibration radiation source is installed above the detection unit 20.

  A door 44 that opens and closes is provided on the rear side of the housing 18. Incidentally, the housing 18 is a waterproof type, and other structures also have a waterproof function. The front edge 45 of the upper surface 18a has an arc shape as will be described later. The front edge 45 corresponds to a boundary line between the upper surface 18a and the front surface 18b.

  FIG. 3 shows a rear view of the monitoring cart. As described above, the door 44 is provided on the rear side of the housing 18. The door 44 has a window 46 through which a display, an operation panel, and the like can be visually observed. When the door 44 is opened, the display and the operation panel are exposed. For example, the measured flying direction is displayed on the display, and the dose rate is displayed. Of course, such a display may be provided on the upper surface. When the detection unit is calibrated, a stand 48 is inserted into the stand jig 42. The stand 48 includes a constituent radiation source (sealed radiation source) 50, and γ rays 52 therefrom are detected by the detection unit. Based on the dose rate and the like at that time, the configuration of the detection unit or calculation unit is performed.

  FIG. 4 shows a top view of the monitoring cart. Reference numeral 110 is a center line passing through the center in the left-right direction. The line 112 is a horizontal line that divides the front region E1, the rear region E2, and the like on the upper surface 18a. The front area E1 is an area having a semicircular shape, and the rear area E2 is a rectangular area. The detection center 52 is specified as the intersection of the line 114 and the line 110. As described above, the indicator lamp 22 is provided in the rear region E2, and the stand jig 42 is provided on the right side thereof. In the present embodiment, a GPS 70 is provided on the left side of the indicator lamp 22. It measures geographic location data.

  A detection unit 20 is provided in the front region E1. As shown in FIG. 4, the entire detection unit 20 enters the front region E1. That is, the outer diameter (diameter) of the cover is smaller than ½ of the diameter that defines the curvature of the front surface 18b. As described above, the housing 18 has the left side surface 18c and the right side surface 18d in addition to the front surface 18b.

  The base plate 12 protrudes in the horizontal direction from the housing 18, and in particular, is formed at a position where the front end face 12A extends forward from the front face 18b. The front end surface 12A has a shape that gently bulges forward.

  The change of the vertical sensitivity characteristic according to the direction in the scintillator member will be described with reference to FIG.

  As described above, the front surface 18a of the housing 18 forms a semi-cylindrical surface, and when viewed from above, the front edge 45 exists in an arc shape so as to surround the scintillator member 38. The front edge 45 corresponds to the edge of the housing 18. Incidentally, reference numeral 20A denotes a cover.

  As shown in FIG. 5, when all the center directions are set to 0 degrees and, for example, directions of 30 degrees, 60 degrees, 90 degrees, and 120 degrees are defined in the clockwise direction, in this embodiment, It is possible to specify the flying direction over a range of 120 degrees on the right and left sides. In that case, the detection limit angle in the vertical direction continuously changes over a range of about 120 degrees from 0 degree to the right side and the left side.

  (A) to (E) schematically show detection limit angles. The schematic diagram shown in (A) corresponds to a vertical sectional view corresponding to 0 degrees. In such an orientation, the radiation having the largest angle among the radiations from obliquely below that can be detected by the scintillator member 38 without passing through the housing 18 is indicated by reference numeral 102A. It reaches the scintillator member 38 through the vicinity of the front edge point 45 </ b> A corresponding to the edge in the housing 18. In this case, the detection limit angle is represented by φ1. In practice, radiation that partially passes through the housing 18 can also be observed, but such radiation is attenuated by the housing 18, and the detection limit angle is defined by radiation that is not attenuated by the housing 18. Has been. (B) shows a detection limit angle φ2 corresponding to an azimuth of 30 degrees. The radiation 102B flying at such an angle passes through the vicinity of the leading edge point 45B. (C) shows a detection limit angle φ3 corresponding to an azimuth of 60 degrees. The radiation 102 </ b> C passes near the front edge point 45 </ b> C in the housing 18 and reaches the scintillator member 38. (D) shows a detection limit angle φ4 corresponding to an azimuth of 90 degrees. The radiation 102D passes through the vicinity of the front edge point 45D in the housing 18 and reaches the scintillator member 38. (E) shows a detection limit angle φ5 corresponding to an orientation of 120 degrees. The radiation 102E passes through the vicinity of the front edge point 45E in the housing 18 and reaches the scintillator member 38.

  As described above, the front surface 18b constitutes a semi-cylindrical surface, and the front edge 45 has a semicircular shape accordingly. The distance to the edge changes smoothly, and as a result, the detection limit angle changes smoothly from the azimuth of 0 degrees to the vicinity of the right and left azimuths of 120 degrees. In other words, the vertical sensitivity characteristics or directivity characteristics change smoothly, and it does not change irregularly or suddenly, so the direction determination accuracy can be stabilized or the direction determination accuracy can be improved. Is possible. Of course, if the curvature center of the front surface 18b and the detection center 52 are made to coincide, the sensitivity characteristic in the vertical direction can be made uniform over a wide angle range in the front, but in such a case, the processing cost tends to increase. For this reason, it is desirable to adopt the configuration as in this embodiment. By the way, there is an operator behind the monitoring cart, and the monitoring cart is basically pushed forward and operated by that person. There is no need to do it. Of course, by devising the shape of the housing, it is possible to make the sensitivity characteristics uniform even in such an orientation.

  Incidentally, it is possible to reduce the orientation dependence of the vertical sensitivity characteristic by processing such as tilting the edge of the upper surface, but in such a case, processing cost increases and the volume in the housing is unnecessarily increased. Therefore, in this embodiment, the upper surface is configured as a flat surface, and the front surface is configured as a semi-cylindrical surface.

  FIG. 6 shows a comparative example. In this comparative example, the housing 54 has a completely rectangular shape when viewed from above, and its front surface 56 is flat. As a result, the leading edge 54A is a straight line. In such a configuration, (A) shows a detection limit angle with an azimuth of 0 degrees. As shown in the figure, the detection limit angle is φ6. It is also defined by the radiation that passes near the leading edge 56A of the housing 54. On the other hand, (B) shows a detection limit angle φ7 corresponding to an azimuth of 60 degrees. Since the housing 54 has a rectangular shape when viewed from above, and the horizontal distance between the center of the scintillator member 38 and the front edge point 56B is the largest at an azimuth of 60 degrees, the detection limit angle φ7 is considerably small. . That is, when a contamination source is located at a relatively close point in the direction, the contamination source may not be sufficiently detected. Moreover, it can be pointed out that the sensitivity characteristic in the vertical direction changes greatly with the azimuth of 60 degrees as a boundary.

  On the other hand, according to the monitoring cart of this embodiment, as shown in FIG. 5, the vertical sensitivity characteristic, that is, the detection limit angle can be smoothly changed over a wide azimuth range in front, and the detection limit Since the angle can be made relatively large, it is possible to detect the radiation from the contamination source with high sensitivity even when approaching the contamination source. Incidentally, in identifying the contamination source, the traveling direction of the monitoring cart is often directed to the contamination source, and the direction in which the contamination source exists is often at or near 0 degrees. Therefore, in the present embodiment, the detection limit angle is large near the azimuth of 0 degrees, and the detection limit angle decreases as the distance from the detection limit increases.

  FIG. 7 shows a block diagram of the monitoring cart. The detection unit 20 includes a scintillator member 38 and three photomultiplier tubes 58, 60, and 62 that detect light generated there. The scintillator member 38 has a disk shape, for example, and is divided into three blocks every 120 degrees. A photomultiplier tube is provided for each block. The ratio of the three count values detected using the three photomultiplier tubes changes according to the radiation direction of radiation, and it is possible to specify the direction of radiation radiation with such a ratio change. It is.

  The high voltage source 64 supplies electric power to the three photomultiplier tubes 58, 60 and 62. The signal processing unit 66 applies known signal processing such as pulse height discrimination and pulse shaping to the electrical pulses output from the photomultiplier tubes 58, 60, and 62. The pulse after the signal processing is applied. Is sent to the control unit 68.

  The control unit 68 is constituted by, for example, a microcomputer, and includes an azimuth calculation unit 70. The azimuth calculating unit 70 determines the radiation flight azimuth from the mutual ratio of three count values or coefficient rates obtained by using three photomultiplier tubes. The data representing the radiation flight direction as the determination result is sent to the display unit 74, where the radiation flight direction is displayed as a numerical value or a vector symbol.

  The input unit 72 is configured by a switch or a keyboard, and a predetermined input can be made to the control unit 68 using the input unit 72. The indicator lamp 22 is lit when the dose rate exceeds a certain value. You may comprise so that a display mode may change according to the magnitude of a dose rate. The GPS 76 acquires geographical location data, and the location data is sent to the control unit 68. A communication unit 78 is connected to the control unit 68, and an antenna 80 is connected to the communication unit 78. If necessary, the control unit 68 adds position data to the azimuth measurement result and transmits them to the central center as radio waves via the communication unit 78 and the antenna 80. The power supply unit 82 includes a battery 84 configured by a primary battery or a secondary battery. The power supply unit 82 supplies power to the control unit 68 and other components.

  As described above, according to the monitoring cart according to the present embodiment, the form of the leading edge is determined so as to surround the detection unit, and thereby, the sensitivity dependence in the vertical direction, specifically the detection limit angle, depends on the orientation. Therefore, the orientation specifying accuracy can be improved. Further, since the housing has a simple form, the dead volume inside the housing can be reduced, and the processing cost of the housing can be reduced. In the present embodiment, since the detection limit angle is the largest at the azimuth of 0 degrees, it is possible to improve the sensitivity characteristic in the vertical direction in the direction in which the monitoring cart 10 travels in identifying the actual contamination source. Furthermore, in the present embodiment, a base plate is provided below the housing, whereby background radiation flying from the lower side can be reduced.

  In the above-described embodiment, an annular direction indicator is provided around the detection unit, and when the direction is determined, the direction can be accurately read in relation to the detection unit.

  10 monitoring cart, 11 base unit, 12 base plate, 18 housing, 20 detector, 22 indicator lamp, 24 direction indicator.

Claims (6)

A base unit having a plurality of wheels;
A housing provided on the base unit;
A handle member gripped by an operator standing on the rear side of the housing;
A detection unit including a radiation detector installed at a central position in the left-right direction on the upper surface of the housing and higher than the upper surface level of the housing;
An azimuth calculation unit for specifying the azimuth of radiation as a horizontal direction based on the output signal of the detection unit;
Including
The housing has a front surface having a shape of a semi-cylindrical surface swollen forward,
The front edge of the upper surface of the housing is curved in an arc around the detection unit,
A monitoring cart characterized by that. The monitoring cart according to claim 1,
The upper surface of the housing has a semicircular front side region and a rear side region continuous therewith,
The detection unit is installed in the front region,
A monitoring cart characterized by that. In the monitoring cart according to claim 1 or 2,
The radiation detector is a scintillator member;
The detection unit includes a dome-shaped cover that houses the scintillator member,
A monitoring cart characterized by that. The monitoring cart according to any one of claims 1 to 3,
The base unit has a base plate having a radiation shielding effect or an attenuation effect,
The base plate extends forward from the front surface;
A monitoring cart characterized by that. The monitoring cart according to any one of claims 1 to 4,
On the upper surface of the housing, an azimuth indicator that is referred to when specifying the radiation azimuth is provided,
A monitoring cart characterized by that. The monitoring cart according to claim 5,
The orientation indicator is an annular scale provided around the detection unit,
A monitoring cart characterized by that.