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Hazama, Osamu; Araya, Fumimasa
Nihon Kikai Gakkai 2007-Nendo Nenji Taikai Koen Rombunshu, Vol.1, p.685 - 686, 2007/09
A new concept of double-wall-tube steam generator (SG) is being introduced and investigated as an innovative technology to realize next-generation sodium-cooled Fast Breeder Reactors (FBRs) for commercialization. This new concept is posing great challenges in the engineering design of a tubesheet which must bundle over 7000 double-wall tubes under severe mechanical and thermal loads. R&D efforts concerning the development of a feasible design and establishment of design-by-analysis methods for the new-concept tubesheet structure have been begun at JAEA. As a first step, an attempt at identifying the high stress locations and their magnitudes through large-scale numerical simulations using geometrical models in accord with reality are reported.
Kasahara, Naoto; Takasho, Hideki*; Ando, Masanori
Nihon Kikai Gakkai 2007-Nendo Nenji Taikai Koen Rombunshu, Vol.1, p.683 - 684, 2007/09
Tubesheet structures utilized in heat exchangers have complex perforated portions. For design analysis of these structures, axi-symmetric models with equivalent materials of perforated plate are conventionally adopted to simplify perforated portions. Double wall steam generators expected for commercial FBRs require new type of tubesheets, where conventional design methods are not applicable. Therefore, JAEA started research programs to develop a design by analysis method of these structures. This paper reports on the mechanism of thermal stress developments in new tubesheets with an associated paper.
Bubphachopt, B.*; Watanabe, Osamu*; Kawasaki, Nobuchika; Kasahara, Naoto
Nihon Kikai Gakkai 2007-Nendo Nenji Taikai Koen Rombunshu, Vol.1, p.689 - 690, 2007/09
This study reports the real-time observation results on fatigue phenomena of the perforated plate and the half circular- hole notched plate made of SUS 304 stainless steel at elevated temperature. The crack initiates on the surface from the hole-side in the thickness direction and the crack initiates from the mid-surface along the thickness direction. After the crack initiation, it propagates and coalesces to fail finally. The number of micro or mini crack is summarized as a function of applied cyclic number.
Wakai, Takashi; Takahashi, Yukio*
Nihon Kikai Gakkai 2007-Nendo Nenji Taikai Koen Rombunshu, Vol.1, p.401 - 402, 2006/09
This paper describes metallurgical observation and analysis results for the aged welds made of Gr.91 and Gr.122 steels. Much more coarse carbides were observed by SEM in the fine grain heat affected zone of the welds than in the base metal and coarse carbides increased with aging. However, extracted residue analyses showed that the total amount of precipitations did not depend on regions and did not increase with aging. Therefore, the carbides which had precipitated in the early stage of aging cohered and grew mainly on the prior austenite grain boundaries, as far as the welds were subjected to stress free isothermal aging for 6,000 hours.