| Project/Area Number |
09044117
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| Research Category |
Grant-in-Aid for Scientific Research (B).
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Materials/Mechanics of materials
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| Research Institution | Tohoku University |
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Principal Investigator |
SHOJI Tetsuo Graduate School of Engineering, Tohoku University Prof., 大学院・工学研究科, 教授 (80091700)
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| Co-Investigator(Kenkyū-buntansha) |
MINKOV DORIAN Graduate School of Engineering, Tohoku University Ass. Prof., 大学院・工学研究科, 助教授 (30291264)
WATANABE Yutaka Graduate School of Engineering, Tohoku University Ass. Prof., 大学院・工学研究科, 助教授 (10260415)
SAKA Masumi Graduate School of Engineering, Tohoku University Prof., 大学院・工学研究科, 教授 (20158918)
NAKAJIMA Mikiko Graduate School of Engineering, Tohoku University Lec., 大学院・工学研究科, 講師 (80005488)
RAJA KRISHNAN SELVA Graduate School of Engineering, Tohoku University Res. Ass., 大学院・工学研究科, 助手 (40302179)
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| Project Period (FY) |
1997 – 1999
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| Keywords | Environmentally Assisted Cracking / Structural materials of Nuclear Reactor / Crack Growth / Nondestructive inspection / Micro Sampling / Water Chemistry / Slip-dissolution Model |
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| Research Abstract |
Assuring the safety of nuclear power plants is an important issue all over the world. Especially the quantitative evaluation of environmentally assisted cracking (EAC) of materials in high temperature water is critical. However, EAC is affected by so many factors that estimation is not accurate enough up to now.
This is a cooperative research that combines the fundamental research achievements on EAC of the leader of this project with the research results of Russian researchers who possess rich data of practical nuclear reactors. Main achievements can be summarized as follows :
(1) The relation between corrosion fatigue crack growth rate and the shape of MnS inclusions has been studied. It has been shown that the size distribution of the inclusions is more important than the total sulfur content in steel. Reactor pressure vessel steel made by Russian that has high sulfur content but well distributed small particles of MnS inclusions was evaluated in Tohoku University. Results showed that
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the higher crack growth rate expected only from the sulfur content was not observed.
(2) Detection method for small defects have been studied. The validities of induced current focusing potential drop (ICFPD) technique and direct current potential drop (DCPD) technique using adjacent probes were confirmed. A cooperative research project on how to detect inside defects in stainless steel welds from the outer surface has been set up for the future. The materials will be prepared by Central Institute of Structural Materials in Russian. The evaluation will be done in Tohoku University.
(3) The relation between aging degradation of surface film and EAC has been studied. The research results on contact electric resistance and other electric properties accompanying film growth were exchanged. According to the electric property change with film growth during irradiation, the relation to irradiation assisted stress corrosion cracking has been made clearer.
(4) Investigation for improvement for EAC incidents of VVER type nuclear power plants and, strong methods of material test has been done. Defect detection and crack growth rate evaluation have been suggested.
(5) EAC at condensation pail of low pressure seam turbine has been researched. A practical plan about experimental facilities and analysis has been suggested. It has been made clear that Kelvin probe is useful for evaluating corrosion in the thin water layer condition. The experiments have been carried out partly. Less
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