JP2001305278A - Low-activated shielding vessel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the activation of a stainless outer shell plate for covering a vessel body by thermal neutrons. SOLUTION: The outside of the vessel body 2 made of stainless structural material is covered with a shielding concrete layer 4 through a heat insulating material 3. The outside of the shielding concrete layer 4 is covered with a thermal neutron absorbing concrete layer 8 containing boron. The outside of the thermal neutron absorbing concrete layer 8 is covered with the stainless material outer shell plate 5. The thermal neutrons generated in the shielding concrete layer 4 are absorbed by boron of the thermal neutron absorbing concrete layer 8 to avoid the activation of the stainless material outer shell plate 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low activation shielding container used as a vacuum container for accommodating a nuclear fusion device.

[0002]

2. Description of the Related Art In a vacuum vessel used to house a nuclear fusion device, not only shielding performance but also low activation is important.

[0003] Therefore, this kind of conventional vacuum vessel is shown in FIG.
(B) As shown in (b), the cylindrical portion and the upper lid portion of the container body 2 are made of a stainless steel structural material, and the outside thereof is covered with a shielding concrete layer 4 of a required thickness via the heat insulating material 3. In addition, there is provided a vacuum vessel 1 having a structure in which the outside of the shielding concrete layer 4 is covered with a stainless steel outer shell plate 5. Reference numeral 6 denotes a vacuum exhaust port, and reference numeral 7 denotes a container support.

[0004]

However, in the case of the above-mentioned conventional vacuum vessel 1, since neutrons are mainly shielded by the shielding concrete layer 4, the heat generated in the shielding concrete layer 4 is eliminated. If neutrons activate the stainless steel outer shell plate 5 over time with the neutrons, there is a possibility of exposure.

[0005] Therefore, the present invention is to prevent the outer shell plate made of stainless steel from being activated by thermal neutrons.

[0006]

According to the present invention, in order to solve the above-mentioned problems, the outside of the container body is covered with a concrete layer for shielding, and the outside of the concrete layer for shielding is heated with boron. The concrete layer for thermal neutron absorption is covered with a concrete layer for thermal neutron absorption, and the outside of the concrete layer for thermal neutron absorption is covered with a shell plate made of stainless steel, and the amount of boron contained in the concrete layer for thermal neutron absorption. Is set to about 1%.

[0007] Since the outside of the shielding concrete layer is covered with a boron-containing concrete layer for absorbing thermal neutrons, thermal neutrons that cause activation can be absorbed by the concrete layer for absorbing thermal neutrons. The outer stainless steel shell plate can be prevented from being activated.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. As in the case of the vacuum container shown in FIGS. 2A and 2B, the outside of a container body 2 made of stainless steel is successively heat-insulated. 3. In the configuration in which the concrete layer 4 for shielding and the outer shell plate 5 made of stainless steel are covered in layers, the thermal neutron absorption is provided between the concrete layer 4 for shielding and the outer shell plate 5 made of stainless steel. A low-energy radiation shielding container in which a thermal neutron absorbing concrete layer 8 impregnated with about 1% of boron (boron) as a material is interposed and arranged.

The thickness of the thermal neutron absorbing concrete layer 8 is, for example, about 5 cm when the thickness from the inner surface of the container body 2 to the outer surface of the outer shell plate 5 is 30 cm.
The amount of boron added to the thermal neutron absorbing concrete layer 8 was set to about 1% because the amount of boron added was 1% in order to absorb thermal neutrons.
% Is necessary and sufficient.

Since boron impregnated in the thermal neutron absorbing concrete layer 8 absorbs thermal neutrons which cause activation, the thermal neutrons generated in the shielding concrete layer 4 can be absorbed by boron. Thermal neutrons can be blocked by the neutron absorbing concrete layer 8. Therefore, the activation of the outer shell plate 5 can be prevented, and the exposure of workers to radiation can be prevented. Further, since the activation of the outer shell plate 5 can be avoided, embrittlement of the stainless steel material which is the material of the outer shell plate 5 can be suppressed.

It should be noted that the present invention is not limited to only the above embodiment, and the concrete layer 8 for absorbing thermal neutrons is used.
Can be arbitrarily selected, and various changes can be made without departing from the scope of the present invention.

[0013]

As described above, according to the low activation container of the present invention, the outside of the container main body is covered with the concrete layer for shielding, and the outside of the concrete layer for shielding is heated with boron. Covered with a neutron absorbing concrete layer,
The outer surface of the thermal neutron absorbing concrete layer is covered with a stainless steel outer shell plate, and the amount of boron contained in the thermal neutron absorbing concrete layer is about 1%. The thermal neutrons generated in the shielding concrete layer can be blocked by the thermal neutron absorbing concrete layer, which prevents the activation of the outer shell plate made of stainless steel. I do.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view of a part of a low activation shielding container according to an embodiment of the present invention.

FIGS. 2A and 2B show an example of a vacuum vessel, wherein FIG. 2A is a schematic side view of the whole, and FIG. 2B is an enlarged sectional view of a portion A of FIG.

[Description of Signs] 2 Container body 4 Concrete layer for shielding 5 Shell plate 8 Concrete layer for absorbing thermal neutrons

Claims (2)

[Claims] 1. A concrete for thermal neutron absorption, wherein the outside of the container body is covered with a concrete layer for shielding, and the outside of the concrete layer for shielding is covered with a concrete layer for thermal neutron absorption containing boron. A low-energy shielding container having a structure in which the outside of a layer is covered with an outer shell plate made of stainless steel. 2. The low activation shielding container according to claim 1, wherein the amount of boron contained in the thermal neutron absorbing concrete layer is about 1%.