Hitachi, Ltd.

Jun'ya Kaneda

Takahiko Kato

Tetsuya Nagata

Hisanori Okamura

Yasuhisa Aono

Kunihiko Suzuki

Toshimi Matsumoto

Tsutomu Onuma

Keiichi Uraki

Akira Onuma

Mitsuo Nakamura

Toshitaka Satsuta

In a case of welding a highly neutron-irradiated austenitic stainless steel, the portion to be welded is heated under a condition of temperature and time in a predetermined range before welding. In this moment, chromium carbide (Cr.sub.23 C.sub.6) precipitates in the grain boundaries of the stainless steel. Welding is performed the state described above is obtained. Since, chromium carbide has been precipitated in the grain boundary by the heat treatment before welding, any helium atoms generated through nucleus conversion of Ni, are apt to be trapped with the chromium carbide, thereby reducing the number of gas bubbles formed by gathering the helium atoms in the grain boundaries. As a result, since decrease in the strength of the grain boundaries due to helium gas bubbles is moderated, it is possible to prevent occurrence of cracks during welding.

Method of welding neutron irradiated metallic material

A neutron-irradiated structural material having a defect in a nuclear reactor internals is repaired by covering the structural material to be repaired with a plate to cover over a portion thereof having the defect, and then welding the plate and the structural material by locally applying pressure on the surface of the plate and adding energy to the portion to which the pressure is applied thereby to generate thermal energy in the contact surfaces between the plate and the structural material.

Method of repairing structural materials of nuclear reactor internals

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Hitachi, Japan

Jun'ya Kaneda