JPS6262304B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a radiation area monitor for measuring radiation intensity distribution in a nuclear power plant or the like.

(Prior Art) Conventionally, in order to know the radiation environment of a nuclear power plant or the like, an area monitor in which a radiation detector is fixedly installed at a location representative of the environment has been used. This detector has no directivity and is fixed, so it is not possible to know the radiation intensity at the location where it is installed.
It is not possible to know the radiation intensity at locations where no such devices are installed. Therefore, in order to monitor the radiation environment, radiation control personnel use portable radiation measuring devices to survey the target area and create iso-radiation dose rate distribution maps.

(Problems to be solved by the invention) These operations are difficult when the radiation environment changes.
This required a great deal of labor as it was carried out each time work was carried out within the target area.

The present invention has been made in view of the above-mentioned drawbacks, and it is an object of the present invention to provide a radiation area monitor that can determine the radiation intensity distribution over the entire radiation environment using a small number of fixed detectors.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, the present invention includes a plurality of radiation direction detectors that output angular dose distributions and input signals from the plurality of radiation direction detectors. A radiation area monitor is provided, comprising a signal processing circuit that calculates a radiation source intensity and a radiation intensity distribution, and a display circuit that displays the radiation intensity distribution from the output of the signal processing circuit.

(Function) In the radiation area monitor configured in this way, multiple radiation direction detectors are installed in the radiation environment including the back side of various equipment, etc. It is now possible to obtain the angular dose distribution of It becomes possible to display it.

(Example) Hereinafter, an example of the radiation area monitor according to the present invention will be described with reference to FIGS. 1 to 9.

FIG. 1 is a configuration diagram showing an embodiment of the radiation area monitor according to the present invention, which is a slit type that can rotate 360° about the X, Y axes (2 axes) or the X, Y, and Z axes (3 axes). A radiation direction detector (hereinafter referred to as radiation detector) 11 having a collimator of
A, 11B, and electronic circuits 18A, 18B that analyze the angular dose distribution from the incident direction of radiation at a certain measurement point and the radiation dose rate incident from that direction,
an electronic circuit 20 that stores and analyzes the position of the radiation source and the radiation intensity from the angular dose distribution at two or more points, stores information over a certain period of time obtained at the plurality of points, and calculates an iso-radiation dose rate distribution map of the surrounding environment; It consists of a display device 22 for illustrating the radiation dose on a diagram of the environment, and a recording device 24.

The radiation detectors 11A, 11B have radiation detection elements 13A, 13B disposed at the center inside of spherical shields 12A, 12B, and have angle meters 15A, 15B above. The radiation detection elements 13A, 13B are connected to the electronic circuit 18 via power cables and detector output signal cables 16A, 16B, and the output signals of the angle meters 15A, 15B are connected to the electronic circuit 18 via signal cables 17A, 17B.
It is connected to A and 18B. Electronic circuit 18A,
The output signal of 18B is also connected to the signal processing circuit 20 via signal cables 19A and 19B. Further, the output signal of the signal processing circuit 20 is led to a display device 22 via a signal cable 21, and is also input to a recording device 24 via a signal cable 23 as required. Note that the radiation detectors 11A, 11B are provided with slits 14A, 14B in the shape of notches.

The electronic circuits 18A, 18B are the detection elements 13A, 1
3B and the goniometers 15A, 15B are input via signal cables 16A, 16B, 17A, 18B to determine the angular dose distribution of the incident radiation. Further, the electronic circuit 20 is the electronic circuit 18A, 18
The B signal is inputted via signal cables 19A and 19B, and the radiation dose in the surrounding environment is determined from the location of the radiation source and the radiation intensity. The display device 22 receives the signal 21 from the signal processing circuit 20 and displays the radiation dose distribution on a drawing of the environment, and the recording device 24 receives the signal 23 from the display device 22 and displays the radiation dose rate at preset coordinates. Output. Angle meter 15A, 15
B is the rotation angle of the slits 14A and 14B,
Detection is performed in each of the Y and Z directions.

Next, the shielding bodies 12A and 12B constituting the radiation detectors 11A and 11B are
As shown in the figure. Here, FIG. 2 shows the shielding bodies 12A, 1
2B is a perspective view, FIG. 3 is a cross-sectional view of FIG. 2 taken along the - line and viewed from the arrow direction, and FIG. 3 is a cross-sectional view of FIG. 2 taken along the -- line and viewed from the arrow direction.
The shielding bodies 12A, 12B have radiation detection elements 13A, 13 at the center thereof, as shown in FIGS. 2 to 4.
A slit 1 is provided on the surface including the detection elements 13A and 13B.
4A and 14B are provided. The shielding body 1
The thicker the thickness _t1 of 2A and 12B, the more the slit 14A,
The radiation dose outside 14B is reduced, and the slits 14A,
It becomes possible to detect the amount of radiation that passes through the detector 14B and enters the detectors 13A and 13B. Further, the width _t2 of the slits 14A and 14B is preferably narrow in order to improve the angular resolution. However, if the slits are made too narrow, the amount of radiation passing through the slits 14A and 14B will decrease, making detection difficult. Therefore, the width t ₂ of the slits 14A, 14B, the shields 12A, 1
Regarding the thickness _t1 of 2B, etc., it is necessary to select appropriate conditions depending on the radiation situation at the measurement point. Note that the cable 16 connected to the detection elements 13A and 13B
A, 16B are guided to the outside through curved passages 26A, 26B provided in the shields 12A, 12B. By bending these passages 26A and 26B, radiation from these parts is prevented.

The rotation axes of the radiation detectors 11A and 11B can be adjusted in the X, Y, and Z axis directions by a drive device as shown in FIG. That is, the support rotation shafts 111A and 111B are the rotation function transmission members 112.
Drive motor 113A, 1 via A, 112B
13B rotates 360° in the direction of arrow _Y1 . The support rotation shafts 114A and 114B are the rotation function transmission member 1
Drive motor 116 via 15A, 115B
A, 116B rotates 90 degrees in _{the two} directions of arrow Y. Due to the rotation of the shafts 114A and 114B, the shaft 1
11A and 111B rotate and stand up from a horizontal position (XX axis direction) to a vertical position (YY axis direction) via members 119A and 119B fixed to shafts 114A and 1114B. Moreover, the radiation detector 11
A, 11B are rotation function transmission members 117A, 117
It is rotated 90 degrees in the direction of arrow _Y3 by drive motors 118A and 118B via B.

Next, the operation of this embodiment will be explained with reference to FIG. 6. First, the two radiation detectors 11A and 11B shown in FIG. 1 are fixedly installed at appropriate locations in a radiation environment. Now, one radiation detector 11
A is set at point O in FIG. 6, and the direction of incidence of radiation is the direction of arrow C. The radiation detector 11A is moved by the drive device shown in FIG.
The radiation dose passing through the slit 14A by rotating it through 360 degrees about the Y and Z axes is measured together with the slit angle, and is led to an electronic circuit 18A shown in FIG.

That is, first, the slit 14 is placed in the position shown in FIG.
Assuming that there is A, the support rotating shaft 111A coincides with the XX axis direction. The support rotation shaft 111A is connected to the drive motor 11 by the rotation function transmission member 112A.
When the slit position is rotated 360° in the direction of arrow _Y1 by driving with 3A, the slit position will be on the horizontal plane (X
- The maximum dose is obtained at the position where the rotation angle from the Z plane is θ _X2 .

Next, the drive motor 117A rotates the shaft 111A direction by 90 degrees in the direction of arrow _Y4 , so that the shaft 111A coincides with the Z-Z axis direction. At this position, the shaft 111
When A is rotated in the direction of arrow _Y1 , the maximum dose is obtained when the slit position is at a rotation angle of θ _Z1 from the horizontal (XZ plane) as shown in FIG. Next, the shaft 114A is rotated once using the drive motor 116A, and the support member 119A is rotated by 90 degrees, so that the direction of the shaft 111A coincides with the Y-Y axis. When the shaft 111A is rotated in the direction of arrow _Y1 at this position, the slit position will be at the 6th position.
The rotation angle from the vertical plane (Y-Z plane) shown in the figure is θ _ys
The maximum dose is obtained at .

Each slit angle and radiation dose measured in the above procedure are input to the electronic circuit 18A. The electronic circuit 18A has a slit rotation angle θ _x2 of the X, Y, and Z axes,
The radiation incident direction is determined from the intersection point c ₁ of θ _ys and θ _z1 and the dose, and after converting the vertical angle to the horizontal angle, the angular dose distribution is calculated. Note that the same applies when the radiation incident direction is in the arrow A direction and the arrow B direction.

Note that the intersection of the slit angles can be expressed by the following equation, and the direction of incidence can be determined only when this equation is satisfied.

sin ² θ _x = (sin ² θ _z + sin ² θ _x −tan ² θ _z × sin ² θ _x ) sin ² θ _y … However, if there is another incidence on the same slit angle for each axis, use the above formula. Even if the angle is satisfied, it cannot be concluded that there is an incident, so the electronic circuit 18A analyzes the radiation dose by taking into consideration the radiation dose, converts the vertical angle to the horizontal angle using the following equation, and outputs the result.

It is also possible to detect the slit rotation angle by providing an angle meter pulse transmitter or a suitable encoder attached to the support rotation shaft 111A to output an electric signal proportional to the rotation angle.

On the other hand, radiation detector 1 installed at another location
For 1B, the radiation incident direction and angular dose rate distribution at that location are determined using the same procedure.

The signals obtained by the electronic circuits 18A and 18B in the above procedure are led to the signal processing circuit 20, the location of the radiation source and the radiation intensity are determined, and the radiation dose rate of the surrounding environment is determined.

The method will be explained with reference to FIG. Two radiation detectors 18A and 18B shown in FIG. 1 are now installed at measurement points A and B, respectively. The distance between measurement points A and B is a, the vertical angle of the incident radiation is θ _yA and θ _yB , and the horizontal angle is η, respectively.
If _A and η _B , the position of the radiation source D will exist at the intersection of their extensions, and the distance L from the measurement point A to the radiation source D at that time can be determined as satisfying the following equation.

(Cos ² θ _yA・sin ² η _B・Cos ² η _A −Cos ² θ _yB・sin ² η _A・Cos ² η _B )L ² Cos ² η _A −(2aCosθ _yA・sin ² η _B・Cos ² η _A ) LCosη _A +a ² sin ² η _B・Cos ² η _A = 0... Based on the distance to the source obtained using the above formula, the angular dose rate distribution at the measurement point, and the shape of the source, the radiation intensity of the source can be determined. can be found.

In the above, the distance to the source, the shape of the source,
When determining the radiation intensity of a radiation source, there is no problem if the radiation source is a point radiation source, but if the radiation source is a distributed radiation source, it can be determined by the following method. The method will be explained with reference to FIG. 8, taking as an example the case of a radiation source distributed in a plane.

Regarding the radiation source 215, if the angle of incidence of radiation at measurement point A is θ _A and the angle of incidence of radiation at measurement point B is θ _B , the apparent shape of the source obtained from the measurement results is determined by these angles θ _A , _θB
This is a hatched portion 216 surrounded by .
In other words, it is evaluated as having a larger shape than the solid line source 215.

Moreover, when further measured at measurement point C, θ _C
The apparent shape of the source obtained from the measurement results is based on these angles θ _A , θ _B , θ _C
This is a portion 217 surrounded by. That is,
The results obtained at three measurement points are closer to the solid line source 215 than the results obtained at the two measurement points A and B described above. Furthermore, the more measurement points are added, the closer they are to the solid radiation source 215.

Furthermore, the radiation dose of the radiation source 215 is determined by the angle θ
It can be assumed that the radiation exists as a point at the intersection of the angles with the highest dose rates in _A , θ _B , and θ _C , or it can be assumed that the radiation is evenly distributed over the entire source determined above. . Which of these two methods to adopt should be determined based on the allowable error, etc.

After determining the shape and radiation intensity of the radiation source, the radiation dose rate of the surrounding environment is calculated using an attenuation calculation formula. If there are multiple sources, the dose rate for each source is calculated and summed.

The signal of the radiation dose rate of the surrounding environment obtained above is led to the display device 22 and displayed on the drawing of the surrounding environment. The display method will be explained with reference to FIG. 9.

A screen 21 of a display device 22 showing a layout drawing of devices 212, 213, etc. installed in the surrounding environment as shown in FIG.
Let it be displayed on 1. Then, based on the radiation dose determined by the electronic circuit 20 shown in FIG.
4 is displayed on the screen 211. In this case, with one radiation direction detector (not shown), it is not possible to obtain dose rate data on the back side of the devices 212 and 213 with respect to the radiation direction detector. Therefore, in order to obtain an accurate radiation dose distribution map, a plurality of radiation direction detectors are required. In order to obtain the distribution map shown in FIG.
It is necessary to install radiation direction detectors at three locations behind 13. The isodose line 214 can be accurately displayed from the data obtained from these radiation direction detectors.

Regarding the display method, it is also possible to display each predetermined dose rate range in color or black and white shading.

In addition, if necessary, the screen 21 of the display device 22 may be
The radiation dose rate for each coordinate is also output to the recording device 24 shown in FIG.

〔Effect of the invention〕

According to the present invention, by fixedly installing a plurality of radiation direction detectors in a small number, it is possible to display an iso-radiation dose distribution map with high accuracy even in places where complex radiation sources exist, so radiation environment monitoring can be performed in detail. It can be carried out easily and without much effort.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of a radiation area monitor according to the present invention, FIG. 2 is a perspective view showing an example of a slit-type collimator used in the radiation area monitor, and FIG. Figure 4 is a cross-sectional view of Figure 2 taken along the - line and viewed from the direction of the arrow.
The figure is a perspective view showing the driving device of the slit-type collimator, FIG. 6 is an explanatory view showing the direction of incidence of radiation,
Figure 7 is an explanatory diagram for determining the position of the radiation source from the incident direction and angular dose rate diagram obtained at two measurement points. FIG. 9 is an explanatory diagram showing the radiation dose rate of the surrounding environment displayed on the screen. 11A, 11B... Radiation detector (radiation direction detector), 12A, 12B... Shielding body, 13A, 1
3B... Radiation detection element, 14A, 14B... Slit, 15A, 15B... Angle meter, 18A, 18B...
Electronic circuit, 20... Signal processing circuit, 22... Display device, 24... Recording device, 16A, 16B, 17A,
17B, 19A, 19B, 21, 23...signal cable, 25A, 25B...radiation detector storage space,
26A, 26B...bent signal cable passage, 1
11A, 111B, 114A, 114B...rotating shaft, 113A, 113B, 116A, 116B,
118A, 118B... Drive motor, 112A,
112B, 115A, 115B, 117A, 11
7B...Rotation function transmission member, 119A, 119B...
Support member, 211... Display device screen, 212... Equipment, 213... Equipment serving as a radiation source, 214... Iso-dose rate line, 215... Distributed radiation source, 216... Apparent radiation source when measured at two points, 217... Apparent radiation source when measured at three points.

Claims (1)

[Claims] 1. A radiation detection element, a shielding member that stores the radiation detection element in a central space and has a narrow slit in its upper half for a collimator of the radiation detection element, and rotates the slit so that at least one axis is aligned with the slit. supporting shafts set in parallel; a drive member that is provided to engage with each of the supporting shafts and independently adjusts and sets a desired rotation angle for each of the supporting shafts; and a drive member that engages with each of the supporting shafts. A plurality of radiation direction detectors each comprising a detection member provided to detect the rotation angle of the slit, and an electronic circuit for determining the angular dose distribution of radiation at an arbitrary point from the signal of the radiation detection element and the rotation angle of the slit. and a signal processing circuit that inputs signals from the plurality of radiation direction detectors to calculate the radiation source intensity and radiation intensity distribution, and a display circuit that displays the radiation intensity distribution from the output of this signal processing circuit. A radiation area monitor featuring: