JPS5945952B2 - 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 radioactive contamination in the environment, it was necessary to carry a radiation detector to the desired location, and in order to determine the state of contamination over a wide range, a large number of measurement points were required. The problem was that the amount of radiation exposure was also quite large.

Moreover, with conventional methods, measurement values have large errors due to the influence of the surrounding environment, and it is not possible to automatically monitor the radiation dose distribution at all times.

For example, in nuclear power plants, main facilities, main equipment surfaces,
There is a strong desire for a device that continuously and automatically measures radiation dose distribution from pipes, floors, walls, etc.

In view of the above points, the present invention provides a radiation telescope that can automatically and continuously measure the radiation dose distribution from a predetermined object to be measured at a position remote from the object to be measured.

In the radiation telescope according to the present invention, a collimator having a radiation transmission hole having a predetermined opening angle with respect to the object to be measured is used, and a plurality of radiation detectors are arranged behind the collimator.

Further, a scanning drive means is provided for rotating these radiation detector groups around the central axis of the collimator.

Then, the output of each radiation detector is amplified by a sense amplifier, and the outputs of these amplifiers are processed to obtain a two-dimensional radiation distribution from a predetermined range of the object to be measured.

The present invention will be described in detail below with reference to the drawings.

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 θ 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, a plurality of radiation detectors 3 (31 , 32...3n) are arranged at approximately equal intervals,
Radiation from the object to be measured 4 in front is detected.

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 arrangement 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.

Specifically, as shown in FIG. 3, these radiation detectors 3 are fixed to a pedestal 9 with their respective incident surfaces perpendicular to the radiation from the collimator.

This frame 9 has a rotating shaft 1 coaxial with the central axis of the collimator 1.
0, and is rotationally driven by a scanning drive means (not shown) such as a motor, thereby measuring the radiation dose distribution within a predetermined solid angle range from the center of the collimator.

The outputs of the radiation detectors 3 are each sent to a sense amplifier 5 (51
, 52...5n), performs waveform shaping if necessary, removes noise with a wave height discrimination circuit, etc.
Enter.

The processing device 6 has a storage device, for example, and each radiation detector 3
The radiation output signal is temporarily stored using the position and rotational angle position on the frame 9 as address information.

Then, this is read out and a two-dimensional radiation dose distribution is displayed on a display device 17 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 radiation dose is displayed in different colors using, for example, a color cathode ray tube as the display device 7, it is possible to determine at a glance which part of the object to be measured 4 has a high radiation dose and the extent of the radiation dose. can.

Of course, the radiation dose may be displayed by brightness using a black and white cathode ray tube.

As described above, by using the radiation telescope of this embodiment, the radiation distribution from the object to be measured can be automatically and continuously measured and monitored at a position remote from the object to be measured.

Therefore, there is no need for the measuring person to approach the measuring point with the detector, which is a dangerous task, and by using a collimator with a radiation-transmitting hole with a predetermined opening angle relative to the object to be measured, it is possible to avoid the influence of the surroundings. It is possible to accurately measure the distribution of radioactive contamination within a certain range without being affected.

Furthermore, since the two-dimensional radiation dose distribution is measured by rotating and scanning a plurality of groups of radiation detectors, accurate monitoring of radioactive contamination over a wide range can be performed using a relatively small number of radiation detectors.

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

When used in a place where a radiation source with low γ-ray energy is used, in addition to the above materials, for example, copper, beryllium,
Aluminum, 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, NaI scintillators or semiconductor detectors are preferred when the gamma ray energy is high, and plastic or semiconductor detectors are preferred when the gamma ray energy is low.

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 obtain the radiation dose distribution for a specific radionuclide. be.

As described above, the radiation telescope according to the present invention can measure the radiation dose distribution at a position far from the measurement point, so there is little risk of radiation exposure to the human body, and moreover, it can accurately cover a wide range with a relatively small number of radiation detectors. It is possible to measure radiation dose distribution and is extremely useful for monitoring radioactive contamination in the environment.

[Brief explanation of the drawing]

Figures 1a and b are diagrams showing the structure of a collimator in an embodiment of the present invention, Figure 2 is a diagram showing the schematic configuration of a radiation telescope in the same embodiment, and Figure 3 is a diagram showing the specific structure of the radiation detector group. FIG. 1... Collimator, 2... Radiation transmission hole, θ...
Opening angle, 3...(31,3□,...3n)...
Radiation detector, 4... measured object, 5 (51,5□,
...5n)...Sense amplifier, 6...Processing device,
7... Display device, 8... Recording device, 9...
- Frame, 10...Rotation axis.

Claims (1)

[Scope of Claims] 1. A collimator having a radiation transmitting hole having a predetermined opening angle with respect to the object to be measured, a plurality of radiation detectors arranged behind the collimator, and a group of these radiation detectors arranged as described above. A scanning driving means for rotating the collimator around the central axis, a plurality of sense amplifiers for amplifying the output of each of the radiation detectors, and a plurality of sense amplifiers for processing the output of each of these sense amplifiers to detect a signal from a predetermined range of the object to be measured. A radiation telescope characterized by comprising means for determining a dimensional radiation dose distribution. 2. The radiation telescope according to claim 1, wherein the collimator has radiation transmitting holes cut into a conical shape from the front and back surfaces of a plate having low radiation transmittance.