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Katsuyama, Jinya; Masaki, Koichi; Onizawa, Kunio
Proceedings of 2012 ASME Pressure Vessels and Piping Conference (PVP 2012) (DVD-ROM), 9 Pages, 2012/07
When weld defects are found by inspection after welding, partial repair welding need to be performed after removing the defects. The partial repair welding has a possibility to produce locally high tensile stress. In this study, we have performed thermal-elastic-plastic analyses to evaluate the weld residual stress produced by repair welding after piping butt-welding. The analysis results were validated through the comparison with experimental measurements. From the analysis results with varying the repair welding conditions, it was found that deeper cutting depth causes higher tensile residual stress at the partial welded region. We also performed structural integrity assessments related to SCC using the weld residual stress distribution calculated and probabilistic fracture mechanics analysis code PASCAL-SP. It was clarified that partial repair welding might have an effect to decrease the break probability of piping welds.
Onizawa, Kunio; Masaki, Koichi; Katsuyama, Jinya
Proceedings of 2012 ASME Pressure Vessels and Piping Conference (PVP 2012) (DVD-ROM), 7 Pages, 2012/07
In order to apply a probabilistic fracture mechanics (PFM) analysis to the structural integrity assessment of a reactor pressure vessel (RPV), PFM analysis code has been developed at JAEA. Using the PFM analysis code, PASCAL version 3, the conditional probabilities of crack initiation and fracture for an RPV during pressurized thermal shock events have been analyzed. Sensitivity analyses on some input parameters were performed to clarify the effect on the conditional fracture probability. Comparison between the conditional probabilities obtained from PASCAL3 analyses and a temperature margin (
T
) from current deterministic analysis method were made for some model plant conditions of domestic typical old-type RPVs. From the analyses, a good correlation between T and the conditional probability of crack initiation was obtained.
Yamamoto, Masato*; Kimura, Akihiko*; Onizawa, Kunio; Yoshimoto, Kentaro*; Ogawa, Takuya*; Chiba, Atsushi*; Hirano, Takashi*; Sugihara, Takuji*; Sugiyama, Masanari*; Miura, Naoki*; et al.
Proceedings of 2012 ASME Pressure Vessels and Piping Conference (PVP 2012) (DVD-ROM), 7 Pages, 2012/07
Master curve (MC) approach for the fracture toughness evaluation is expected to be a powerful tool to assess the structural integrity of reactor pressure vessels (RPVs). In order to get sufficient number of reliable data for the MC approach from broken halves of surveillance test specimens for RPVs, the use of miniature specimens is necessary. For this purpose, a round robin test program on the miniature compact tension specimens (Mini-CT) of 4 mm thick for the MC approach of a Japanese RPV steel has been launched with the participation of academia, industries and a research institute in Japan. The program aims to verify the reliability of experimental data from Mini-CT, and to pick out further investigation items to be solved. As the first step of this program, four institutes carried out MC testing and evaluation using common test procedure and specimens. Valid reference temperature T
was successfully obtained in each institute. However, the T values showed large differences with maximum of 34
C. It was indicated on the reason of difference that there is a strong correlation between the T values and loading rate, which was selected by each institute per test standard.
Wakai, Takashi; Machida, Hideo*; Yoshida, Shinji*
Proceedings of 2012 ASME Pressure Vessels and Piping Conference (PVP 2012) (DVD-ROM), 9 Pages, 2012/07
This paper describes the efficiency of the deployment of rotational stiffness evolution model in the critical crack size evaluation for Leak Before Break (LBB) assessment of Sodium cooled Fast Reactor (SFR) pipes. The authors have developed a critical crack size evaluation method for the thin-walled large diameter pipe made of modified 9Cr-1Mo steel. In this method, since the SFR pipe is mainly subjected to displacement controlled load caused by thermal expansion, the stress at the crack part is estimated taking stiffness evolution due to crack into account. The stiffness evolution is evaluated by using the rotational spring model. In this study, critical crack sizes for several pipes having some elbows were evaluated and discuss about the effect of the deployment of the stiffness evolution model at the crack part on critical crack size. As a result, the critical crack size increases by employing the model and LBB range may be expected to be enlarged.
Ando, Masanori; Kanasaki, Hiroshi*; Date, Shingo*; Kikuchi, Koichi*; Sato, Kenichiro*; Takasho, Hideki*; Tsukimori, Kazuyuki
no journal, ,
To assess the failure estimation methods, cyclic thermal loading tests of cylindrical models with thick part were performed. In the tests, crack initiation and propagation processes at stress concentration area were observed by replica method. Besides those, finite element analysis (FEA) was carried out to estimate the number of cycles to failure. The crack initiation life was in a good agreement with the FEA result by considering the short term compressive holding. Through these test and FEA results, fatigue and creep-fatigue life assessment methods of Mod.9Cr-1Mo steel including evaluation of cyclic thermal loading, short term compressive holding and failure criterion, were discussed.
Nishida, Akemi
no journal, ,
Because an arrangement of a piping structure is very complicated in a nuclear facility, the structural safety is used to be evaluated every structural part. However, evaluation for structural safety in entire is very important in the case of evaluation of the response for earthquakes loads, etc. In this presentation, the wave propagation model which we developed is applied to the cooling piping structure in a model plant, and the response propagation characteristics are investigated. Also the differences of response characteristics with different propagation property at the support points are investigated and the obtained results are shown.