JPS6049264B2 - radiation telescope - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a radiation telescope useful for monitoring radioactive contamination of the environment.

Conventionally, in order to measure the radioactive contamination status of the environment, it was necessary to carry a radiation detector to the place to be measured.
In order to determine the state of contamination over a wide area, a large number of measurement points are required, which poses a problem in that the amount of radiation exposure of the person taking the measurements is quite large.

Moreover, with conventional methods, the measurement values have large errors due to the influence of the surrounding environment, and it is not possible to automatically monitor the radioactive contamination density distribution at all times. For example, in nuclear power plants and the like, there is a strong desire for a device that continuously and automatically measures radioactive contamination density distribution on main facilities, main equipment surfaces, piping, floors, walls, etc. In view of the above-mentioned points, the present invention provides a radiation telescope that can automatically and continuously measure the radioactive contamination density distribution from a predetermined object to be measured at a position away from the object to be measured.

That is, the present invention includes a collimator having a radiation transmitting hole having a predetermined opening angle with respect to the object to be measured, a radiation detector equipped with at least one set of automatic rangefinders arranged behind the collimator, and the rangefinder. and a first scanning drive means for moving the radiation detector in a circular arc centering on the radiation transmitting hole within a plane including the central axis of the collimator, and moving the automatic range finder and the radiation detector at the center of the collimator. and a second scanning drive means for rotating around the axis. In the radiation telescope according to the present invention, a collimator having a radiation transmitting hole having a predetermined opening angle with respect to the object to be measured is used, and a radiation detector equipped with at least one automatic distance meter is arranged behind the collimator.

The automatic rangefinder and radiation detector are driven to scan within a predetermined solid angle range from the center of the collimator, with their radiation incident surfaces always kept perpendicular to the radiation from the collimator. That is, a first scanning driving means moves the radiation detector in a circular arc centering on the radiation transmitting hole of the collimator within a plane including the central axis of the collimator, and a second scanning driving means rotates around the central axis of the collimator. scanning drive means. Then, the output of the radiation detector scan-driven in this way is amplified by a pulse amplifier, and the output of this amplifier and the automatic distance meter output are processed by a process computer etc. together with the scan drive information of the radiation detector to detect the object to be measured. Find the radioactive contamination density distribution from a predetermined range. below,
An embodiment of the apparatus according to the present invention will be described with reference to FIGS. 1 to 3.

FIGS. 1A and 1B are a plan view of the collimator 1 and a sectional view thereof taken along the line AA''.

The collimator 1 is made of a plate made of lead, tungsten, or the like having low radiation transmittance, and has a radiation transmitting hole 2 cut into a conical shape from the front and back surfaces thereof. In the case of the figure, the radiation transmitting hole 2 has an opening angle of O with respect to the object to be measured. FIG. 2 is a schematic diagram of a radiation telescope configured using such a collimator 1. Behind the collimator 1 is an automatic range finder 11 that is driven to scan in a substantially spherical manner with the radiation transmission hole 2 as the center. A radiation detector 3 equipped with a radiation detector 3 is arranged to detect radiation from an object 4 to be measured in front. The measurement range of the object to be measured 4 is determined by the opening angle θ of the radiation transmission hole 2 of the collimator 1 and the scanning range of the radiation detector 3. The radiation detector 3 is, for example, a NaI scintillator, a plastic scintillator, a semiconductor radiation detector, or the like. The automatic distance meter 11 is, for example, an optical type using a visitronic module. It is an automatic focal length meter. Specifically, the radiation detector 3 and the automatic distance meter 11 are installed on a pedestal 9 having a surface including the central axis of the collimator 1 as shown in FIG. The first scanning drive means and the pedestal 9 are collimated. The radiation detector 3 is provided with a second scanning drive means that rotates around the rotation axis 10 coaxial with the collimator 1 as shown by an arrow. A roughly spherical surface is drawn with . The output of the radiation detector 3 is amplified by a pulse amplifier 5, subjected to waveform shaping if necessary, noise removed by a pulse height discrimination circuit, etc., and then input to a processing device 6.

The processing device 6 is, for example, a process computer and has an internal storage device and a calculation function, and addresses the positions of the radiation detector 3 and the automatic distance meter 11 on the pedestal 9, the rotation angle position of the pedestal 9, and the distance meter output. The radiation output signal is temporarily stored as information. In addition to information regarding the direction of the object to be measured, information regarding the distance to the object to be measured is also input as address information, so the calculation function built into the processing device 6 is used to calculate the direction of the object to be measured from the distance information and the radiation output signal. Radioactive contamination density can be calculated. This is read out and a two-dimensional radioactive contamination density distribution is displayed on a display device 7 such as a cathode ray tube. If necessary, the read radiation dose data can be recorded on an external recording device 8 for automatic data collection. If the display device 7 displays the radioactive contamination density in different colors using, for example, a color cathode ray tube, it is possible to see which part of the object 4 to be measured has a high radioactive contamination density and how high the radioactive contamination density is. It can be identified at a glance.

Of course, by a black and white cathode ray tube? Radioactive contamination density may be displayed in terms of brightness. As described above, by using the radiation telescope of this embodiment, it is possible to automatically and continuously measure and monitor the radioactive contamination density distribution from the object to be measured at a position away from the object to be measured.

Therefore, the measuring person does not have to carry out the dangerous work of approaching the measurement point while holding the detector, and by using a collimator with a radiation transmitting hole having a predetermined opening angle with respect to the object to be measured, it is possible to detect the surroundings. It is possible to accurately measure the radioactive contamination density distribution within a defined range without being affected. Further, by scanning and driving a radiation detector equipped with one automatic distance meter, it is possible to measure a two-dimensional radioactive contamination density distribution and to accurately monitor radioactive contamination over a wide range. Note that in order to measure the distance from the radiation detector to the object to be measured through the collimator, it is preferable to make the fields of view of the radiation detector and the automatic distance meter as close as possible. For example, as shown in Figure 4a, a radiation detector as small as possible,
A small automatic distance meter is placed side by side. Alternatively, as shown in FIG. 4b, a more preferable method is to place the automatic rangefinder coaxially with the radiation detector by reflecting only visible light using a mirror that absorbs little radiation. Furthermore, if two radiation detectors and two automatic distance meters are used to share the scanning range on the pedestal, it is possible to measure the same radioactive contamination density distribution by driving the pedestal for half a rotation.

In addition to lead and tungsten, molybdenum, gold, tantalum, and platinum are also preferred as materials for the collimator because they have low radiation transmittance.

When used in a place where a radiation source with low gamma ray energy is used, in addition to the above-mentioned materials, for example, copper, iron, nickel, or an alloy thereof can also be used. Furthermore, a suitable radiation detector may be selected depending on the radiation energy to be measured. For example, when the γ-ray energy is high, a NaI scintillator or a semiconductor detector is preferable, and when the γ-ray energy is low, a plastic scintillator is also used in addition to the above detector. Furthermore, by using a radiation detector that has output linearity with respect to radiation energy and selecting its discrimination level using a pulse height discrimination circuit, it is possible to use the radioactive contamination density distribution for a specific radionuclide. It is possible.

As described above, since the radiation telescope according to the present invention has an automatic distance meter attached to the radiation detector, it is possible to detect the radioactive contamination density distribution at a position far from the measurement point without knowing the location of the object to be measured in advance. The risk of radiation exposure to the human body is low, and the combination of two scanning drive means allows accurate radioactive contamination density distribution over a wide range to be obtained using one or two sets of radiation detectors and an automatic distance meter. It is very useful for monitoring environmental radioactive contamination.

[Brief explanation of the drawing]

FIG. 1a is a front view showing the structure of a collimator in an embodiment of the present invention, FIG. Figure 2 is a conceptual diagram showing the schematic configuration of the radiation telescope of the same embodiment, Figure 3 is a model diagram showing the specific scanning drive of the radiation detector and distance meter according to the present invention, and Figures 4A and b. 1 is a sectional view showing the arrangement of a radiation detector and an automatic distance meter in an embodiment of the present invention. 1... Collimator, 2... Radiation transmission hole, O... Opening. Corner, 3... Radiation detector, 4... Body to be measured, 5... Pulse amplifier, 6... Processing device, 7... ... Display device, 8... Recording device, 9...
Frame, 10...rotation axis, 11...automatic distance meter, 12...mirror.

Claims (1)

[Claims] 1. A collimator having a radiation transmitting hole having a predetermined opening angle with respect to the object to be measured, and a radiation detector equipped with at least one set of rangefinders arranged behind the collimator;
a first scanning driving means for moving the rangefinder and the radiation detector in a circular arc centering on the radiation transmission hole within a plane including the central axis of the collimator; and a second scanning drive means for rotating the collimator around its central axis.