JPH0634775A - Vacuum container for nuclear fusion device - Google Patents

Abstract

PURPOSE:To provide a radioactivity lowering vacuum container which has a satisfactory electric resistance function, a high mechanical strength and which may serve as a hydrogen or hydrogen isotope container. CONSTITUTION:An aluminum layer 2 formed on the inner surface of a vacuum container 1 and a titanium layer 3 are metallurgically joined together so as to serve as an integral container. With the use of the combination of the aluminum layer 2 and the titanium layer 3, the function required for the vacuum container serving as a hydrogen or hydrogen isotope storage container, and the electric resistance function and the mechanical strength may be satisfied.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a nuclear fusion device and its vacuum container aiming at low emission.

[0002]

2. Description of the Related Art A vacuum container of a conventional nuclear fusion apparatus is made of a material such as stainless steel or high nickel steel (Inconel, etc.) so that the electric resistance value required for the container, atmospheric pressure and electromagnetic force can be improved. The structure was designed to satisfy the strength. However, since stainless steel and Inconel steel are activated by the irradiation of fast neutrons generated in the fusion reaction, there is a problem that they serve as a radiation source for the living body and other devices (coils, etc.) that constitute the fusion device.

On the other hand, aluminum (or aluminum alloy), titanium (or titanium alloy), etc. have been considered as materials for the vacuum container for satisfying the purpose of low emission. However, aluminum (or aluminum alloy) has high electric conductivity (that is, low electric resistance), and it is necessary to make the member thin in order to satisfy the predetermined electric resistance required for the fusion vacuum container,
For this reason, there is a drawback in that it is difficult to provide the container with sufficient strength against the atmospheric pressure applied as the external pressure and the electromagnetic force load. Also, titanium (or titanium alloy)
Has an electrical conductivity similar to that of stainless steel and high strength, so that it is possible to satisfy the electrical resistance and strength aspects as a vacuum container of a nuclear fusion device. However, in the operation of the fusion device, in order to generate plasma of hydrogen or hydrogen isotope in its operation, the vacuum container needs to function as hydrogen or hydrogen isotope storage container. Easy to adsorb and store
(See P.72, FIG. 3 ・ 31), therefore, there is a problem that the material becomes brittle by absorbing hydrogen.

[0004]

As described above, in a fusion vacuum container that requires low radiation, the electrical resistance performance and mechanical strength (atmospheric pressure resistance, required) of the vacuum container are required.
It has been more difficult than ever to satisfy both the requirement of (electromagnetic force resistance) and the feasibility of hydrogen or hydrogen isotope containment.

The present invention has been made in order to solve such a conventional problem, and is a low activation vacuum container having a low electric resistance and a high mechanical strength, and the material becomes fragile due to the absorption of hydrogen. It is an object of the present invention to provide a vacuum container for a nuclear fusion device that does not include

[0006]

In order to achieve the above object, titanium (or titanium alloy) is used as an electric resistor and a structure as a material composition of the vacuum container of the fusion device and a method of sharing the functions thereof in the present invention. It is used as a strength member, and as a vacuum boundary material for storing hydrogen or a hydrogen isotope, aluminum (or an aluminum alloy) or a material similar to this, which has low emission and does not have a problem of coexistence with hydrogen, is used.

Furthermore, a surface treatment is applied to the inner surface of the titanium (or titanium alloy) container in order to set a vacuum boundary for storing hydrogen or hydrogen isotope.

[0008]

With the structure of the vacuum container of the present invention, in the vacuum container of the nuclear fusion device which is required to have low radiation, the electric resistance performance and mechanical strength (atmospheric pressure resistance, electromagnetic force resistance) required for the container. , It is possible to simultaneously satisfy the feasibility as a hydrogen or hydrogen isotope storage container. Because the electrical resistivity of aluminum is 2.7 × 10 ^{-8 at} room temperature.
Ωm, whereas titanium has 5.5 × 10 ⁻⁷ Ωm. That is, when titanium is used for a certain electric resistance value required for the vacuum container, the plate thickness can be about 20 times that of aluminum. In addition, titanium has a higher material strength than aluminum. On the other hand, in the conventional design example using the aluminum material, it was difficult to secure a sufficient plate thickness and the insufficient strength of the container was a serious problem, but if titanium is used as the strength member as described above, It will be very advantageous in designing the strength of the container.

[0009] Compared with titanium alloys, aluminum alloys
By arranging an aluminum alloy inside a titanium alloy, which is a low activation material, the radiation dose rate in the vacuum container can be reduced.

[0010]

1 is an explanatory view showing the material constitution and structure of a vacuum container according to a first embodiment of the present invention. In FIG. 1, the inner surface side of the vacuum container 1 is composed of an aluminum (or aluminum alloy) layer 2 to provide a vacuum boundary and function as a container for storing hydrogen or hydrogen isotopes. The outer surface of the vacuum container 1 is made of titanium (or titanium alloy), which satisfies the electric resistance performance and mechanical strength required for the vacuum container. The aluminum (or aluminum alloy) layer 2 and the titanium (or titanium alloy) layer 3 are metallurgically bonded or mechanically bonded to function as an integral container. Here, as a method of metallurgical joining, explosive welding (although it is difficult to weld) or brazing using aluminum brazing is possible, and explosive welding is suitable in this structure. As a mechanical joining method, general bolt connection can be applied. Here, if the aluminum layer is thin, it is difficult to bolt it directly to the plate, so weld the pedestal for bolt mounting onto the aluminum plate.
It is necessary to devise the structure such as brazing and attaching a titanium wall structure. As the structure of the titanium (or titanium alloy) layer, a double wall structure may be used from the viewpoint of strength improvement and shielding performance. An example of a concrete design for this embodiment is shown in FIG. FIG. 5 shows the large radius R as shown.
An example is a simple torus vacuum container structure with v = 4 m and small radius av = 1 m. The toroidal resistance in the toroidal direction required for a tokamak-type fusion device of this scale is several tens.
It is μΩ. This value fluctuates depending on the plasma conditions, but here, it is set to 50 μΩ as a standard value. Circular resistance Rt of the toroidal direction of the vacuum container is approximately Rt = η × RV / (av × t) η: specific resistance of material Rv: large radius of vacuum container av: small radius of vacuum container t: plate of vacuum container Expressed in thickness. Here, aluminum (specific resistance 2.7 × 10
^{If a} vacuum container is configured with a single layer plate of ^-8 Ωm) and a circular resistance of 50 μΩ in the toroidal direction is secured, the designed plate thickness is 2.2 mm. An aluminum material vacuum container having a large radius of 4 m and a small radius of 1 m and a plate thickness of this level is insufficient in strength against atmospheric pressure and electromagnetic force load. On the other hand, when the two-layer structure of aluminum and titanium is used as in this embodiment, the strength can be remarkably improved by titanium. As an example of design, large radius 4m, small radius 1
m, aluminum material plate thickness 1 mm, titanium plate thickness 20 mm, the toroidal resistance of the vacuum container is 54.
It becomes μΩ and achieves 50 μΩ or more. Moreover, the strength of this structure is remarkably increased as compared with the aluminum single layer (about 2 mm thick) structure.

FIG. 2 shows another embodiment showing the material constitution and structure of the vacuum container as the second embodiment of the present invention. The wall material 2 of the vacuum container is made of aluminum (or an aluminum alloy), thereby providing a vacuum boundary and functioning as a container for storing hydrogen or hydrogen isotopes. The outer surface of the container is provided with a titanium (or titanium alloy) rib-reinforcing structure (3a, 3b) to satisfy the electric resistance performance and mechanical strength required for the vacuum container. The aluminum (or aluminum alloy) wall and the titanium (or titanium alloy part) rib-reinforced structure are metallurgically bonded or mechanically bonded. Brazing using aluminum brazing is suitable as an example of metallurgical joining in this case. As a design example for this embodiment, a simple torus vacuum container having a large radius of 4 m and a small radius of 1 m is taken as described above. Aluminum plate thickness is 1
mm, titanium reinforcing material width 100 mm, plate thickness 20 m
When 50 m-shaped toroidal ribs are attached (in this case, the rib plate installation pitch in the poloidal direction is 126 mm evenly distributed), the toroidal circumferential resistance of the vacuum container is approximately 61 μΩ, which is required to be 50 μΩ or more. Be satisfied. Although the vacuum container of FIG. 2 includes both the rib 3a in the toroidal direction and the rib 3b in the poloidal direction, only one of them may be provided.

Further, FIG. 3 shows a third embodiment of the present invention in which, of the vacuum vessels, the titanium (or titanium alloy) vessel 1 is surface-treated on its inner surface.
The inner surface of the titanium (or titanium alloy) container 1 is provided with a surface treatment layer 2 as surface coating or surface modification so as not to adsorb and store hydrogen or hydrogen isotope. As a surface coating method, vacuum deposition of aluminum is possible. Further, as a surface modification method, there is a method of nitriding (heating the surface in a nitrogen atmosphere by laser irradiation or the like to generate a titanium nitride layer). Typically,
The nitriding treatment is effective because the titanium compound has a smaller hydrogen storage amount and a smaller permeation amount than titanium metal. As the structure of the titanium (or titanium alloy) container 1, a double wall structure or a rib structure (which conforms to the structure of Example 2) may be used from the viewpoint of strength improvement and shielding performance. As a design example, a simple torus vacuum container having a large radius of 4 m and a small radius of 1 m is taken as described above. When the aluminum layer is vapor-deposited and the thickness of the layer is 100 μm and the plate thickness of the titanium structure layer is 40 mm, the toroidal resistance in the toroidal direction of the vacuum container is approximately 55 μΩ, which satisfies the requirement of 50 μΩ or more.

Furthermore, FIG. 4 shows the material constitution and structure of a vacuum container as a fourth embodiment of the present invention. The inner surface side of the vacuum container 1 is composed of an aluminum (or aluminum alloy) layer 2, which provides a vacuum boundary and functions as a container for storing hydrogen or hydrogen isotopes. Here, the inner surface of the aluminum (or aluminum alloy layer) 2 is subjected to a surface treatment, and an aluminum surface treatment layer 4 is provided to improve the chemical stability of the surface. As a surface treatment method, an oxide film treatment method for forming an alumina layer having a thickness of about several tens of angstroms is generally used and can be applied to the present vacuum container. The outer surface of the vacuum container is made of titanium (or titanium alloy),
This satisfies the electric resistance performance and mechanical strength required for the vacuum container. Aluminum (or an aluminum alloy layer) and titanium (or a titanium alloy portion) are metallurgically bonded or mechanically bonded to function as an integral container. The metallurgical joining and mechanical joining methods are the same as in the first and second embodiments. The structure of the titanium (or titanium alloy) layer is 2 from the viewpoint of strength improvement and shielding performance.
A heavy wall structure or a rib structure (which conforms to the structure of Example 2) may be used. Design examples using this embodiment are similar to those of the first and second embodiments. Furthermore, the radiation dose rate in the vacuum container can be reduced.

[0014]

As described above, since the present invention is a low activation vacuum container, the safety is high. At the same time, electrical resistance performance, mechanical strength (atmospheric pressure resistance, electromagnetic force resistance), and feasibility of hydrogen or hydrogen isotope containment vessel, which are required as the basic performance of the vacuum vessel of the fusion device, must be satisfied at the same time. Is possible.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a material configuration and a structure of a vacuum container according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a material configuration and a structure of a vacuum container according to a second embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a material configuration and a structure of a vacuum container according to a third embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a material configuration and a structure of a vacuum container according to a fourth embodiment of the present invention.

5 is an explanatory view showing a torus type vacuum container structure in the embodiment of FIG. 1. FIG.

[Explanation of symbols]

 1 Vacuum container 2 Aluminum layer 3 Titanium layer 3a, 3b Rib reinforcement structure

Continued Front Page (72) Inventor Kimihiro Ioki 2-4-1 Shiba Park, Minato-ku, Tokyo Inside Mitsubishi Nuclear Industry Co., Ltd.

Claims (4)

[Claims] 1. A vacuum container for a nuclear fusion device, wherein an aluminum or aluminum alloy layer is metallurgically or mechanically bonded to an inner wall surface of a vacuum container made of titanium or a titanium alloy. 2. A vacuum container of a nuclear fusion device, wherein a reinforcing member made of titanium or a titanium alloy is bonded to an outer wall surface of a vacuum container made of aluminum or an aluminum alloy. 3. A core characterized in that the surface treatment layer is formed as a hydrogenation-resistant treatment layer on the inner wall surface of a vacuum container made of titanium or a titanium alloy by means such as plating, vacuum deposition, chemical treatment, or ion implantation. Vacuum container for fusion equipment. 4. An aluminum or aluminum alloy layer is metallurgically or mechanically bonded to the inner wall surface of a vacuum container made of titanium or a titanium alloy, and the inner wall surface of the container, which is the surface of the aluminum or aluminum alloy layer, is surface-treated. A vacuum container for a nuclear fusion device, characterized by being subjected to alumite treatment.