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Nakahira, Masataka
JAERI-Research 2005-030, 182 Pages, 2005/09
JAERI-Research-2005-030.pdf:12.57MB
It is difficult for Vacuum Vessel (VV) of ITER to apply a non-destructive in-service inspection (ISI) and then new safety concept is needed. Present fabrication standards are not applicable to the VV, because the access is limited to the backside of closure weld of double wall. Fabrication tolerance of VV is 
5mm even the structure is huge as high as 10m. This accuracy requires a rational method on the estimation of welding deformation. In this report, an inherent safety feature of the tokamak is proved closing up a special characteristic of termination of fusion reaction due to tiny water leak. A rational concept not to require ISI without sacrificing safety is shown based on this result. A partial penetration T-welded joint is proposed to establish a rational fabrication method of double wall. Strength and susceptibility to crevice corrosion is evaluated for this joint and feasibility is confirmed. A rational method of estimation of welding deformation for large and complex structure is proposed and the efficiency is shown by comparing analysis experimental results of full-scale test.
Suzuki, Takayuki*; Usami, Saburo*; Kimura, Takae*; Koizumi, Koichi; Nakahira, Masataka; Takahashi, Hiroyuki*
Proceedings of 55th Annual Assembly of International Institute of Welding (IIW2002), 16 Pages, 2002/06
A new type of welded joint for the outer wall and rib of a double-walled vacuum vessel of a fusion reactor has been developed. The joint is manufactured by through-wall electron-beam welding (TW-EBW), in which the beam is injected from the outside of the outer wall. Static and fatigue tests are carried out on one-bead-specimens under an axial load and two-bead-specimens under a bending load. The experimental results are analytically investigated by FEM. Although this joint is partially penetrated, the net yield strength of the bead is increased by the plastic constraint due to triaxial tensile stress in the weldment. This phenomenon reduces the mean equivalent stress on the bead cross section, and the gross strength of the joint is close to that of a full thickness welded joint. The fatigue-strength reduction factor for low-cycle fatigue life is a little larger than four. The calculated fatigue-crack growth rate in the joint is conservatively calculated by using the maximum stress intensity factor of the crack and the fatigue-crack growth rate given in ASME Code Section XI.
; Saito, T.*; Tsuji, Hirokazu; Takatsu, T.*; Shindo, Masami; Nakajima, Hajime
JAERI-Research 97-032, 20 Pages, 1997/05
JAERI-Research-97-032.pdf:1.78MB
no abstracts in English
Nakahira, Masataka; Oka, Kiyoshi; *; *; *; Oda, Yasushi*; Kajiura, Soji*; Yamazaki, Seiichiro*; *
Purazuma, Kaku Yugo Gakkai-Shi, 73(1), p.54 - 68, 1997/01
no abstracts in English
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JAERI-M 7152, 31 Pages, 1977/07
no abstracts in English
; ; *; *
JAERI-M 6799, 37 Pages, 1976/11
no abstracts in English
