FUNDAMENTAL-STUDY OF TANDEM ELECTRON-BEAM WELDING FOR NUCLEAR-FUSION AND FISSION REACTORS

As the important part of the life extension program for nuclear fissio n reactors and that of the maintenance scheme of blanket of fusion rea ctors, repair welding technique of neutron damaged materials is recogn ized to be one of the most urgent subjects to be established. This wor k provides the potentiality and the critical issues of ''Tandem electr on beam welding technique'' when it is applied to heavily neutron dama ged materials. Where mechanical property degradation due to the displa cement damage and helium production from (n, alpha) reaction makes it very difficult to produce sound welded joint. This paper presents the preliminary results to see the elementary characteristics of the welde d joints produced by Tandem electron beam welding technique. Not only for the stainless steel nor high-nickel alloys, also for stainless ste el to high-nickel alloy welded joints were studied. The tandem electro n beam welding was done at JWRI, Osaka University. By optimizing the d rilling effect from the leading electron beam and the weld defect supp ression effect from the secondary electron beam, weld defect free weld ed joints were obtained with the excellent joint strength and ductilit y. The weld bead shape and penetration characteristics are also provid ed. The present results are quite promising to apply ''Tandem electron beam welding'' to heavily neutron damaged metallic structures and com ponents.