JPH03239998A - Designing method for radiation shielding body - Google Patents

Abstract

PURPOSE:To exactly and quickly execute the calculation by constituting the radiation shielding body so that many measuring points are set onto the radiation dose measuring surface, and a leak radiation dose contributed by all radiation generation sources is calculated with regard to each measuring point. CONSTITUTION:The radiation dose measuring surface 5 is divided by a boundary 7 in accordance with a difference of shielding effects of radiation shielding bodies 4a, 4b. This division is taken widely so that the corresponding shielding body 4a or 4b covers a radiation generating apparatus 2, and to each divided surface, many measuring points 6e are set like a lattice. In such a way, a leak radiation dose in the measuring point 6e on the measuring surface corresponding to the shielding bodies 4a, 4b can be derived by a prescribed expression. Accordingly, from the derived leak ration does, the maximum dose in the measuring points 6a, 6b is derived, and based on this maximum dose, a size such as optimal thickness, etc., of the shielding bodies 4a, 4b can be designed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method of designing a radiation shield for shielding radiation emitted from a charged particle accelerator or the like.

[Conventional technology]

For example, Figure 2 is written on pages 68-71 of ``FY1985 Scientific and Technical Research Data Creation Commissioned Survey Report - Basic Survey on Safety Management of High Energy Accelerator Facilities'' published by Radiation Safety Technology Center Foundation. This is a configuration diagram showing the principle of the conventional radiation shielding design method. 3C is the radiation emitted from one of the radiation generation devices 2 in the direction of maximum intensity, and 4b is the radiation with the maximum intensity. 3c is a transmitting radiation shield, 4a is a radiation shield that is formed integrally with the radiation shield 4b and has a different thickness from the radiation shield 4b at the boundary 4c, and therefore has a different shielding effect, and 3d is a radiation shield. Radiation passing through the body 4a, 5 is a radiation dose measurement surface placed at the boundary of a radiation control area or a room used, 6c is a measurement point provided at the intersection of the radiation 3c and the radiation dose measurement surface 5, 6d is a radiation dose measurement surface This is a measurement point provided at the intersection of 3d and the radiation dose measurement surface 5.

Next, the operation will be explained.

Maximum intensity radiation 3 emitted from one of the radiation generators 2
c and other radiation 3d pass through radiation shields 4b and 4a, respectively, and reach measurement points 6c and 6d on radiation dose measurement surface 5.

Next, a conventional method of calculating leakage radiation dose will be explained.

The amount of radiation generated by the radiation source is expressed as: d is the distance to the measurement point R1, is the thickness of the radiation shield between this distance, is λ is the 1/10th valence layer of this radiation shield, and is the method of radiation and radiation shield. When the angle between the line and the line is θ, the leakage radiation dose H at the measurement points 6c and 6d is given by the following equation.

H=-10λS'nθ ・・・・・・・・・ (
1)2 The measurement points 6c and 6d are appropriately selected based on the following criteria. Since the amount of radiation generated generally has direction dependence, the radiation 3c in the direction of maximum intensity is selected as a representative of the maximum dose from the source. Further, a shielding body 4b having different shielding effects that is likely to have strong radiation passing through it is also selected. Measurement points 6c and 6d corresponding to the respective radiations 3c and 3d thus selected are set in advance on the radiation dose measurement surface 5, and the leakage radiation dose H at the set measurement points 6c and 6d is ) is obtained by the formula. Then, the radiation shield 4a
, 4b, etc. are designed.

[Problem to be solved by the invention]

The conventional radiation shield design method was performed as described above, so when multiple radiation generating devices 2 are arranged in close proximity, such as in a charged particle accelerator 1, the maximum intensity from each radiation generating device 2 is The radiation 3c and the maximum dose on the radiation dose measurement surface 5 do not necessarily correspond at a l:1 ratio, and the measurement point of the maximum dose occurs at the point where the radiation 3c and 3d of each radiation generating device 2 are combined with each other. Sometimes. In order to set such a maximum dose measurement point, it is necessary to calculate all the radiation emitted from all the radiation generating devices 2.
Since it is difficult to judge how much each radiation passes through the radiation shields 4a and 4b, that is, the degree of attenuation effect, it has not been possible to automatically calculate it using a computer or the like. Due to the inaccuracy of this calculation, a safety factor must be taken into account when designing radiation shields, which results in the deployment of excessively large radiation shields, resulting in larger and more expensive facilities. There was an issue of becoming.

This invention was made to solve the above-mentioned problems, and by enabling automatic calculation, it is possible to accurately predict the radiation dose and design a small and inexpensive radiation shield. The purpose is to obtain a design method for shielding bodies.

[Means for Solving the Problems] A method for designing a radiation shield according to the present invention involves setting a large number of measurement points on a radiation star measurement surface divided according to radiation shields having different shielding effects, and For the measurement point, the radiation shielding body is expressed as an infinite plane, and the leakage radiation dose from each radiation source is calculated using the equation (1) above, and the leakage radiation dose at each measurement point is calculated by adding up the leakage radiation doses. It is designed to be calculated.

[For production]

In the method of designing a radiation shield according to the present invention, applying the above equation (1) to the calculation of the amount of leaked radiation from the radiation source to the large number of measurement points can be executed by a computer program. Furthermore, since all the radiation sources contribute to the summed leakage radiation dose at each measurement point, the radiation shield can be designed based on the maximum dose among them.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. 1st
In the figure, parts corresponding to those in FIG. 2 are designated by the same reference numerals, and their explanation will be omitted.

In FIG. 1, 3a is the radiation that passes through the radiation shield 4a among the radiation from all the radiation generating devices 2, and 3b is the radiation that passes through the radiation shield 4a.
6e is the radiation that passes through the radiation shield 4b among the radiation from all the radiation generating devices 2, 6e is the measurement point provided in a grid pattern on the radiation dose measurement surface 5, and 6a is the radiation shield among the measurement points 6e. Measurement point where radiation 3a transmitted through body 4a is concentrated, 6b is radiation shielding body 4b of measurement point 6e
A measurement point 7 on which the radiation 3b that has passed through is concentrated is a boundary on the radiation dose measurement surface 5 corresponding to the boundary 4c between the radiation shields 4a and 4b.

Next, a method of calculating the leakage radiation dose using the above configuration will be explained.

First, the radiation dose measurement surface 5 is covered with the radiation shield 4a.

It is divided by the boundary 7 according to the difference in the shielding effect of 4b.

This division is made wide so that the corresponding radiation shield 4a or 4b covers each radiation generating device 2, and in some cases, each division plane may overlap each other so that the boundary 7 is not formed.Next, each division plane A large number of measurement points 6e are set in a grid pattern.In addition, measurement points are also provided in the maximum dose direction of each radiation generating device 2.

The leakage radiation dose Hi j at point j (measurement point 6e) on the radiation dose measurement surface 5 corresponding to the i-th radiation shield is given by the following equation.

Here, k is the number of the radiation generating device 2, and the other variables are the same as in equation (1) above. Since it is easy to program the above equation (2) into a computer program, the amount of leakage radiation for the arrangement of the radiation shields 4a, 4b having a predetermined size can be immediately determined.

All the radiation leakage amounts Hi j determined by the above equation (2)
are the contributions of all the radiation generating devices 2, respectively. Therefore, it is possible to determine the maximum dose, such as at the measurement points 6a and 6b, from this radiation leakage amount Hij, and design the optimal thickness and other sizes of the radiation shields 4a and 4b based on this maximum dose. can.

〔Effect of the invention〕

As described above, according to the present invention, a large number of measurement points are set on the radiation dose measurement surface, and the leakage radiation dose contributed by all radiation sources is calculated for each measurement point. This makes it possible to design radiation shields to the minimum necessary size, making it possible to miniaturize and inexpensively make equipment for radiation generating devices such as charged particle accelerators. You can get effects that can be made into something.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the principle of a radiation shield design method according to an embodiment of the present invention, and FIG. 2 is a block diagram showing the principle of a conventional radiation shield design method. ■Charged particle accelerator, 2 radiation generation equipment, 3a, 3b
4a and 4b are radiation shields, 5 is a radiation dose measurement surface, and 6a, 6b, and 6e are radiation dose measurement points. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] The leakage radiation dose at the point where radiation emitted from multiple radiation sources passes through a radiation shielding body of a predetermined size and reaches a radiation dose measurement surface placed at a predetermined position is predicted by a predetermined calculation. In the radiation shield design method of designing the radiation shield based on the predicted leakage radiation dose, a large number of measurement points are set on the radiation measurement surface divided according to the radiation shield with different shielding effects, For each measurement point, the leakage radiation dose from each of the radiation sources calculated by representing the radiation shield as an infinite plane and performing the above-mentioned predetermined calculations is summed to determine the leakage radiation dose at each measurement point. A method of designing a radiation shield.