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Udagawa, Makoto; Katsuyama, Jinya; Onizawa, Kunio
Proceedings of the ASME 2010 Pressure Vessels & Piping Conference (PVP 2010) (CD-ROM), 9 Pages, 2010/07
A number of cracks due to primary water stress corrosion cracking (PWSCC) in PWR and Ni-based alloys stress corrosion cracking (NiSCC) in BWR have been observed near Ni-based alloy welds. One of the causes of initiation and growth due to the SCC is high tensile residual stress as well as operating stress. In this study, an analysis code, PASCAL-NP, for the PWSCC/NiSCC growth at the dissimilar metal welds based on probabilistic fracture mechanics (PFM) was developed. This PFM analysis code has a function of SCC growth calculation for some patterns of crack locations and orientations in a probabilistic manner. This code can also evaluate the failure probability of Ni-based alloy welds due to PWSCC/NiSCC. Using this code and results from welding simulations, case studies on PWSCC growth were performed focusing on the location and orientation of PWSCC. Effect of the scatter of PWSCC growth rate on the crack penetration, i.e. leakage is shown in comparison with deterministic analyses.
Katsuyama, Jinya; Nishikawa, Hiroyuki; Udagawa, Makoto; Nakamura, Mitsuyuki; Onizawa, Kunio
Proceedings of the ASME 2010 Pressure Vessels & Piping Conference (PVP 2010) (CD-ROM), 7 Pages, 2010/07
Stainless steel is cladded on the inner surface of reactor pressure vessels (RPVs) for protecting the vessel walls against the corrosion. After weld-overlay cladding and post-weld heat treatments (PWHT), the residual stress still remain. The residual stresses were measured as-welded and PWHT conditions using sectioning and deep-hole-drilling (DHD) techniques. Thermal-elastic-plastic-creep analyses considering phase transformation of base metal using finite element method were performed to evaluate the residual stress. It was shown that there were good agreement of residual stress distribution between sectioning, DHD and analytical results. To take the phase transformation into account is important to improve the accuracy of weld residual stress analysis. Using the calculated residual stress, the stress intensity factor for a postulated flaw during pressurized thermal shock event has been computed. The effect of residual stress on the structural integrity of RPVs was clearly indicated.
Katsuyama, Jinya; Tobita, Toru; Nishiyama, Yutaka; Onizawa, Kunio
Proceedings of the ASME 2010 Pressure Vessels & Piping Conference (PVP 2010) (CD-ROM), 8 Pages, 2010/07
The surveillance tests of representative materials are performed for the safe operation of light water reactors. Although HAZ specimens' data exhibit large scatter because of the inhomogeneous microstructures due to multi-pass welding, code and standard in Japan and USA stipulate the exception of HAZ surveillance specimens. However, the technical basis for the exception is unclear. Therefore, we have started a research on the irradiation embrittlement in HAZ materials. Typical RPV weldments were manufactured to characterize the inhomogeneity of HAZ. Finite element analysis was conducted to draw maps of microstructure distributions in addition to metallurgical observation. Using simulated HAZ materials with different grain size and phase, mechanical properties such as hardness and fracture toughness were measured. Through the comparison, it was clarified that mechanical properties in HAZ depend significantly on the metallurgical structure.
Yamaguchi, Yoshihito; Katsuyama, Jinya; Onizawa, Kunio; Sugino, Hideharu*; Li, Y.*
Proceedings of the ASME 2010 Pressure Vessels & Piping Conference (PVP 2010) (CD-ROM), 8 Pages, 2010/07
Niigata-ken Chuetsu-Oki earthquake occurred, whose magnitude was beyond the assumed one provided in seismic design. Therefore it becomes an important issue to evaluate the effect of such an excessive loading. Fatigue crack growth is usually evaluated by Paris's law using the range of stress intensity factor, 
K. However, since K is inappropriate in a loading condition beyond the small scale yielding, the evaluation method for such a loading condition should be established. In this study, the crack growth behaviors were investigated using austenitic stainless steel and carbon steel. Instead of K, the range of J-integral, J, has been used for the interpretation of experimental data. Applicability of J into the Wheeler model, which express the retardation effect on the crack growth, has been proposed to evaluate the retardation effect. It was indicated that the J-Wheeler model could be applied to predict the crack growth after an excessive loading beyond small scale yielding.
Kimura, Nobuyuki; Kobayashi, Jun; Kamide, Hideki
Proceedings of the ASME 2010 Pressure Vessels & Piping Conference (PVP 2010) (CD-ROM), 9 Pages, 2010/07
In JSFR, the temperature fluctuation at the core outlet region does not have always a sinusoidal waveform but a sharp edged waveform. The temperature shows intermittent and sudden decrease and recovery like a spike form. In this study, the time interval of each wave based on the rainflow method was applied to consider frequency characteristics against the conversion from fluid temperature to thermal stress in structure. The thermal stress obtained from the new method was compared to the results of FEM analysis. It was found that the consideration of frequency characteristics of waves could evaluate the fatigue damage in structure. Furthermore, the frequency characteristics of waves in this method were expressed as the unified curve independent of the velocity. Hereby the new evaluation method could evaluate the thermal fatigue in the reactor.
Mochizuki, Masahito*; Mori, Hiroaki*; Katsuyama, Jinya
Proceedings of the ASME 2010 Pressure Vessels & Piping Conference (PVP 2010) (CD-ROM), 8 Pages, 2010/07
To make clear the effects of residual stress and work hardening on IGSCC behavior in the welds of the austenitic stainless steel with surface hardening, residual stress and hardness in butt-joints of pipes are evaluated by 3D thermo-elastic-plastic analysis. The grain boundary (GB) sliding behavior is examined using constant strain rate tensile test with the numerically simulated tensile residual stress due to welding and surface machining. It was made clear that GB sliding occurred at 561 K. It was also indicated that the GB sliding in cold-rolled one occurred in smaller strain conditions than that in solution treated one, and that the amount of GB sliding increased with added strain. In addition, it was clarified that the GB energy was raised by the GB sliding. It is concluded from these results that the cause of IGSCC in the welds of stainless steel with surface hardening is the increase in GB energy due to GB sliding accelerated by residual stress of welding and surface hardening.
Ando, Masanori; Hirose, Yuichi*; Date, Shingo*; Watanabe, Sota*; Enuma, Yasuhiro*; Kawasaki, Nobuchika
Proceedings of the ASME 2010 Pressure Vessels & Piping Conference (PVP 2010) (CD-ROM), 11 Pages, 2010/07
To verify the strain prediction method of discontinues structures at evaluated temperature, low cycle fatigue tests were carried out with notched specimens made of Mod.9Cr-1Mo. Deformation control fatigue tests and thermal fatigue tests were performed by ordinary uni-axial push-pull test machine and equipments generating the thermal gradient in the notched plate by induction heating. Crack initiation and propagation process during the fatigue test were observed by the digital micro-scope and replica method. Then the ranges of several strain predictions and estimations were compared with the test results. Stress Reduction Locus (SRL) method, simple elastic follow-up method, Neuber's rule method and the methods supplied by elevated temperature design standards were applied. Through these results, the applicability and conservativeness of these strain prediction and estimation methods is discussed.
Takakura, Kenichi*; Tanaka, Shigeaki*; Nakamura, Tomomi*; Chatani, Kazuhiro*; Kaji, Yoshiyuki
Proceedings of the ASME 2010 Pressure Vessels & Piping Conference (PVP 2010) (CD-ROM), 10 Pages, 2010/07
Irradiation Assisted Stress Corrosion Cracking (IASCC) is a matter of great concern as a degradation of core internal components in light water nuclear reactor. Japan Nuclear Energy Safety organization (JNES) had been conducting a project related to IASCC as a part of safety research and development study for the aging management and maintenance of the nuclear power plants. Based on the JNES project results, JNES proposed "IASCC evaluation guide for BWR core internals". The purpose of this paper is to describe the background of the guide, especially crack growth rate (CGR) tests for irradiated stainless steels.
Nishi, Hiroshi; Enoeda, Mikio; Hirose, Takanori; Tsuru, Daigo; Tanigawa, Hisashi
Proceedings of the ASME 2010 Pressure Vessels & Piping Conference (PVP 2010) (CD-ROM), 8 Pages, 2010/07
The first wall of ITER blanket includes beryllium armor tiles joined to CuCrZr heat sink and stainless steel. Therefore dissimilar materials joints are indispensable for fabricating the high heat flux components. Since these joints must withstand thermal and mechanical loads caused by the plasma and electromagnetic force, it is important to evaluate the strength and thermal fatigue life of dissimilar materials joints. When the dissimilar materials joints are subjected by external force and thermal loading, the stress of the joint may indicate singularity at the interface edge. Since the stress singularity may lower the strength of joints, the singularity is evaluated numerically for the various materials combinations and joint configuration to be used in high heat flux components of fusion reactors in this investigation. Moreover, tensile test and elasto-plastic FEM analysis are performed to investigate the fracture behavior of the various joints obtained the FW mock-up.
Hirose, Takanori; Tanigawa, Hiroyasu; Enoeda, Mikio
Proceedings of the ASME 2010 Pressure Vessels & Piping Conference (PVP 2010) (CD-ROM), p.263 - 266, 2010/07
This paper summarizes manufacturing technologies of the water-cooled-solid-breeder blanket module for a fusion reactor using reduced activation ferritic/martensitic steel (RAFM). Although RAFM is very similar to commercial 9 Cr heat resistant steel, RAFM in the blanket is to be used as thin wall structure. Moreover, it is necessary to employ some new manufacturing technologies for the components such as hot-isostatic-pressing and fiber-laser-welding. Some full-scale mock-ups of the blanket have been developed using conventional and newly developed method. The mock-ups have been developed in industrial scale, and the mock-ups demonstrated integrity in the service condition of the blanket without non-nuclear environment. The mock-ups demonstrated their soundness under the service condition of the blanket.
Nakasone, Yuji*; Sato, Kazuyoshi; Takahashi, Yukio*
Proceedings of the ASME 2010 Pressure Vessels & Piping Conference (PVP 2010) (CD-ROM), 5 Pages, 2010/07
no abstracts in English
Wakai, Takashi; Nagae, Yuji; Onizawa, Takashi; Obara, Satoshi; Xu, Y.*; Otani, Tomomi*; Date, Shingo*; Asayama, Tai
Proceedings of the ASME 2010 Pressure Vessels & Piping Conference (PVP 2010) (CD-ROM), 9 Pages, 2010/07
Wakai, Takashi; Machida, Hideo*; Enuma, Yasuhiro*; Asayama, Tai
Proceedings of the ASME 2010 Pressure Vessels & Piping Conference (PVP 2010) (CD-ROM), 6 Pages, 2010/07
Wakai, Takashi; Machida, Hideo*; Arakawa, Manabu*; Enuma, Yasuhiro*; Asayama, Tai
Proceedings of the ASME 2010 Pressure Vessels & Piping Conference (PVP 2010) (CD-ROM), 7 Pages, 2010/07
Wakai, Takashi; Machida, Hideo*; Yoshida, Shinji*; Enuma, Yasuhiro*; Asayama, Tai
Proceedings of the ASME 2010 Pressure Vessels & Piping Conference (PVP 2010) (CD-ROM), 10 Pages, 2010/07
