JP4310883B2 - Low activation shielding container - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a low radiation shielding container used as a vacuum container for storing a fusion device.
[0002]
[Prior art]
A vacuum vessel used for housing a fusion device is important not only for shielding performance but also for low radiation.
[0003]
Therefore, in this conventional vacuum vessel, as shown in FIG. 2 (B) and (B), the cylindrical portion and the upper lid portion of the vessel body 2 are made of a stainless structural material, and the outside thereof is interposed through the heat insulating material 3. Thus, the vacuum container 1 is configured so as to be covered with a shielding concrete layer 4 having a required thickness, and further, the outer side of the shielding concrete layer 4 is covered with an outer shell plate 5 made of stainless steel. Reference numeral 6 denotes an evacuation port, and 7 denotes a container support.
[0004]
[Problems to be solved by the invention]
However, in the case of the conventional vacuum vessel 1, since the neutron is shielded mainly by the shielding concrete layer 4, the thermal neutrons generated in the shielding concrete layer 4 are made of stainless steel on the outside. If the outer shell plate 5 is activated with time, the possibility of exposure will appear.
[0005]
Therefore, the present invention is intended to prevent the outer shell plate made of stainless steel from being activated by thermal neutrons.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the present invention covers the outside of the container body with a shielding concrete layer, and coats the outside of the shielding concrete layer with a thermal neutron absorbing concrete layer containing boron. The outer layer 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%. .
[0007]
Since the outer surface of the shielding concrete layer is coated with a thermal neutron absorbing concrete layer containing boron, thermal neutrons that cause activation can be absorbed by the thermal neutron absorbing concrete layer, and the outer stainless steel layer It becomes possible to prevent activation of the outer shell plate made of material.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0009]
FIG. 1 shows an embodiment of the present invention. Similar to the vacuum container shown in FIGS. 2 (A) and 2 (B), the outside of a container body 2 made of a stainless steel structure is sequentially covered with a heat insulating material 3 and shielded. In the configuration in which the concrete layer 4 and the outer shell plate 5 made of stainless steel are covered in layers, a thermal neutron absorber is interposed between the shielding concrete layer 4 and the outer shell plate 5 made of stainless steel. A thermal radiation neutron absorbing concrete layer 8 impregnated with about 1% of boron (boron) is provided as a low radiation shielding container having a layered interposition.
[0010]
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 reason why the amount of boron added to the thermal neutron absorbing concrete layer 8 is about 1% is that about 1% is necessary and sufficient for absorbing thermal neutrons.
[0011]
Boron impregnated in the thermal neutron absorption concrete layer 8 absorbs thermal neutrons that cause activation, so that thermal neutrons generated in the shielding concrete layer 4 can be absorbed by boron, and the thermal neutron absorption Thermal neutrons can be blocked by the concrete layer 8. Therefore, activation of the outer shell plate 5 can be prevented, and exposure to workers can be prevented. Further, since the activation of the outer shell plate 5 can be avoided, embrittlement of the stainless steel material that is the material of the outer shell plate 5 can be suppressed.
[0012]
In addition, this invention is not limited only to the said embodiment, The thickness of the concrete layer 8 for thermal neutron absorption can be selected arbitrarily, and various changes can be added within the range which does not deviate from the summary of this invention. Of course.
[0013]
【The invention's effect】
As described above, according to the low activation container of the present invention, the outer side of the container body is covered with the shielding concrete layer, and the outer side of the shielding concrete layer is boron-containing concrete layer for thermal neutron absorption. And the outside of the concrete layer for absorbing thermal neutrons is covered with a stainless steel outer shell plate, and the amount of boron contained in the concrete layer for absorbing thermal neutrons is about 1%. Because it is configured, the thermal neutrons generated in the shielding concrete layer can be blocked by the thermal neutron absorbing concrete layer, which can prevent the activation of the stainless steel outer shell plate Excellent is effective.
[Brief description of the drawings]
FIG. 1 is an enlarged sectional view of a part of a container showing an embodiment of a low activation shielding container of the present invention.
FIGS. 2A and 2B show an example of a vacuum vessel. FIG. 2A is a schematic side view of the whole, and FIG.
[Explanation of symbols]
2 Container body 4 Concrete layer for shielding 5 Outer shell plate 8 Concrete layer for absorbing thermal neutrons

Claims (2)

The outside of the container body is covered with a shielding concrete layer, and the outside of the shielding concrete layer is covered with a thermal neutron absorbing concrete layer containing boron, and the outside of the thermal neutron absorbing concrete layer is A low-radiation shielding container characterized by having a configuration in which it is covered with an outer shell plate made of stainless steel. 2. The low radiation shielding container according to claim 1, wherein the amount of boron contained in the thermal neutron absorbing concrete layer is about 1%.

Images