JPH0677067B2 - Radiation shielding structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION << Industrial Application Field >> The present invention is suitable for adoption in facilities that handle high-energy neutrons and high-density neutrons such as fusion reactor facilities, various neutron experimental facilities, and fast breeder reactor facilities. Radiation shielding structure.

<< Conventional Technology >> Conventional nuclear facilities have relatively low neutron energy and neutron density, and reinforced concrete was effective as a shield for these low-density and low-energy particles.

By the way, recently, experimental facilities for handling high-energy neutrons and high-density neutrons have come to be constructed, and the conventional reinforced concrete shields are also used for these experimental facilities. Here, the reinforced concrete shield is constructed in the same manner as a normal reinforced concrete by a concrete composed of aggregate such as gravel and Portland cement, and a frame composed of rebar, but the gravel etc. which is the above aggregate. Contains mineral components such as Fe, Co, Mn, and Eu. Ordinary Portland cement is mixed with iron oxide during the manufacturing process. Further, the skeleton is also a reinforcing bar, and the Fe, Mn, and Co contents due to this reinforcing bar are contained in large amounts in the above-mentioned reinforced concrete shield.

However, when high-energy neutrons and high-density neutrons are shielded by such a reinforced concrete shield, the reinforced concrete that has received these high-energy high-density neutrons has the above-mentioned mineral components (including iron oxide and Fe content due to rebar).
, Is nuclear-destructed by high-energy and high-density neutrons and becomes a radioactive isotope and is activated.

As a result, the shield is activated to a high level, and when working in the experimental facility, the shield is also irradiated with radiation, and the worker is exposed to a large amount of radiation.

In addition, when the facility is dismantled, it is necessary to dispose a large amount of reinforcing steel and concrete as radioactive waste, and the waste disposal cost becomes extremely high.

Therefore, as a technique for solving such a problem, a high energy particle shielding structure as shown in FIG. 3 has been proposed (see Japanese Patent Laid-Open No. 62-32394). That is, the second shield 12 made of a low activation material is detachably arranged in the high energy particle region of the first shield 11 made of reinforced concrete. The second shield 12 made of this low activation material
Since the activation amount is small, it takes a long time to reach a predetermined activation amount, and the number of disassembling can be reduced. In addition, the second shield 12
When the predetermined activation amount is reached, the second shield 12 may be removed from the first shield 11 and replaced with a new one, and the equipment cost and waste treatment cost can be reduced.

<< Problems to be Solved by the Invention >> However, in the above-described known high-energy particle shielding structure in which the second shield 12 is detachably arranged, for example, an extremely high line drawing of an experimental facility or the like is targeted. Although it is effective for the small-scale special facility, the safety of the operator must be considered when exchanging the activated second shield 12, and the exchanging work is extremely complicated. However, there is a problem that the replacement work cost becomes high, and it is not suitable for application to a large-scale facility that is permanently used.

The present invention has been made in view of the above points, and its purpose is to be suitable for use in large-scale facilities that handle high-energy / high-density particles, and yet have extremely low activation,
Therefore, it is an object of the present invention to provide a radiation shielding structure capable of reducing the radiation exposure of facility workers.

<< Means for Solving the Problem >> In order to achieve the above object, in the radiation shielding structure according to the present invention, the outer layer of one surface is formed of a low activation alloy plate and its inner layer from neutron absorbing and shielding material. The panel is laminated, the iron plate is arranged on the other surface, the reinforcing bars are arranged between the panel and the iron plate, and the concrete is poured.

《Operation》 γ-rays and neutron rays are problems in shielding radiation.

A substance with a large specific gravity (for example, lead, iron, etc.) is effective as a shield for γ rays, and a substance containing an element with a small specific gravity (for example, hydrogen) as a shield for neutron rays (for example,
Water) is effective.

In the radiation shielding structure according to the present invention, the low activation alloy material of the outer layer of the two-layer structure used for one surface has a property of being less activated even when receiving a neutron beam.

As the low activation alloy material having the above action and properties,
For example, an aluminum alloy can be mentioned.

Further, the neutron absorbing and shielding material of the inner layer of the two-layer structure is a substance containing an element having a small specific gravity and has a function of absorbing and shielding neutrons.

Examples of the neutron absorbing and shielding material having this action include substances containing elements having a low specific gravity such as boron and hydrogen.

The concrete inside the frame composed of the above two-layer structure shields γ-rays and also contains water composed of the element H ₂ having a small specific gravity, and this water further shields neutron rays.

The water in the concrete is sealed by the frame body composed of the above-mentioned two-layer structure and an iron plate described later, and its escape is prevented. Therefore, the concrete of the radiation shielding structure according to the present invention maintains a high water content state, and thus a high neutron ray shielding state.

Incidentally, when the neutron beam is shielded, as described above, the γ ray may be secondarily generated upon receiving the neutron beam.
The so-called induced radiation gamma rays generated secondarily are shielded by the concrete as described above.

Examples of the concrete include ordinary concrete (which effectively shields γ rays), heavy concrete (which effectively shields strong γ rays), and serpentine concrete (which effectively shields neutron rays).

Further, the iron plate used on the other surface of the frame has a large specific gravity and has an effect of blocking γ rays. Therefore, this iron plate has a function of blocking the above-mentioned neutron-induced γ-rays.

Further, when the radiation shielding structure according to the present invention is constructed, the frame body including the two-layer structure and the iron plate acts as a molding frame for the reinforced concrete structure.

Therefore, after arranging the reinforcing bar, the frame body composed of the above-mentioned two-layer structure and the iron plate is arranged on the outer periphery of the reinforcing bar, and the concrete is placed in the frame body without removing the formwork. The above radiation shielding structure is constructed.

<< Examples >> FIG. 1 is a plan view showing an example of the radiation shielding structure according to the present invention.

Two layers formed by arranging a low activation alloy material 1 also serving as a mold on the outside of one surface of the radiation shielding structure shown in the same figure, and a molding panel 2 functioning as a neutron absorbing and shielding material on the inside. The structure is used, and the iron plate 3 that also serves as a shielding material and a mold is used on the other surface.

A structure composed of reinforcing bars 4 and concrete 5 is filled and arranged inside the frame bodies 1 to 3 which also function as the above-mentioned formwork, and resists external force (earthquake load etc.) as a structural bearing member. still,
Reference numeral 6 denotes a separator which is arranged so as to be bridged between the low activation alloy material 1 as a mold and the iron plate 3.

The cross-sectional dimensions of the low activation alloy material 1, the molding panel 2, the iron plate 3, and the concrete 5 are appropriately changed according to the intensity of radiation.

In the figure, radiation is applied to the low activation alloy material 1 from the direction of the arrow. At this time, activation of the low activation alloy material 1 by irradiation of radiation is extremely small.

Neutron rays that have passed through the low activation alloy material 1 are absorbed and shielded by the molding panel 2 that functions as a neutron absorbing and shielding material. Therefore, the neutron dose reaching the reinforced concrete 4 concrete 5 structure is extremely small, and this small neutron beam is attenuated by the water retained in the concrete 5 sealed by the frames 1 to 3 and Activation of the reinforcing bars 4 and concrete 5 is small due to the irradiation of a small amount of neutron rays.

In this way, most of the radiation emitted from the radiation source to the radiation shielding structure according to the present invention is shielded, but if the energy or density of the neutron beam is very high, the rebar 4
It may reach the concrete 5 structure and generate guided gamma rays. However, in such a case, this induced γ-ray is shielded by the iron plate 3.

2A to 2C are elevation views showing an embodiment of the construction method according to the present invention in the order of construction.

First, in FIG. 1A, the reinforcing bars 4 are arranged on the floor.
Next, in FIG. 2B, a frame of a two-layer structure composed of the low activation alloy material 1 and the molding panel 2 is arranged on one outside of the reinforcing bar 4, and the steel plate 3 is arranged on the outside of the other side. The formwork is arranged.

After that, in FIG. 2C, concrete 5 is poured into the inside of the formwork defined by the two-layer structures 1-2 and the iron plate 3.

The molds 1 to 3 are used as they are as a part of the radiation shielding structure according to the present invention without being removed.

As described above, a wall of a nuclear facility is constructed using the radiation shielding structure according to the present invention.

<< Effects of the Invention >> In the present invention described in detail above, the following effects can be achieved.

(1) It can be suitably applied to small to large scale radiation facilities.

(2) Since the radiation is extremely low and the radiation can be shielded with high efficiency, it can be suitably applied to a facility that handles high-energy and high-density particles, and it is possible to reduce the dose of radiation to the workers of this facility. .

(3) At the time of dismantling, since the activation of the reinforced concrete inside is extremely low, the dismantling work is relatively easy, and the dismantling cost and the waste treatment cost are relatively low.

(4) Since the low activation alloy material and the iron plate can be used as a mold for casting concrete, the construction is easy and the equipment cost is low.

[Brief description of drawings]

FIG. 1 is a plan sectional view showing an embodiment of a radiation shielding structure according to the present invention, and FIGS. 2 (A) to (C) show an embodiment of a method of constructing a radiation shielding structure according to the present invention. FIG. 3 is an elevational view showing in order, and FIG. 3 is an explanatory view showing a known high energy particle shielding structure. 1 …… Low activation alloy material 2 …… Neutron absorption and / or shielding material 3 …… Steel plate 4 …… Reinforcing bar 5 …… Concrete

Claims (1)

[Claims] 1. An outer layer on one surface is formed of a low activation alloy plate, a panel made of a neutron absorbing and shielding material is laminated on the inner layer, and an iron plate is disposed on the other surface, and the panel and the iron plate are provided. A radiation-shielding structure characterized in that reinforcing bars are arranged between and and concrete is placed.