The purpose of this study is to investigate environmental effects on low cycle fatigue crack growth of SUS316. Low cycle fatigue test and periodical observation on inner surface of a hollow specimen was conducted by developing new type of replica observation. The crack growth in PWR environment was measured and the investigation of environmental effects on crack initiation and propagation was conducted. Crack initiation rate of fatigue test in PWR environment is faster than in air condition. Crack pr...
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Environmental Effect on Low Cycle Fatigue Crack Growth of SUS316

The purpose of this study is to investigate environmental effects on low cycle fatigue crack growth of SUS316. Low cycle fatigue test and periodical observation on inner surface of a hollow specimen was conducted by developing new type of replica observation. The crack growth in PWR environment was measured and the investigation of environmental effects on crack growth was conducted. Crack initiation rate of fatigue test in PWR environment is faster than in air condition. Crack initiation is estimated ...
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Environmental Effect on Low Cycle Fatigue Crack Growth of SUS316

The purpose of this study is to generalize P-curve for strain range condition focusing on crack initiation life and crack growth life. The fatigue tests under different constant strain range conditions were conducted in air and the observation of fatigue cracks on specimen surface was also conducted. Using data derived from experiment, dispersion of cry using two-parameter Weibull distribution. Furthermore, the relationship between strain range and shape parameter or scale parameter of crack initiation mo...
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Study on fatigue crack initiation model in air for type 316 stainless steel

The purpose of this study is to investigate environmental effects on low cycle fatigue crack growth rate of SUS316 in different strain rate condition. The fatigue tests were conducted under different strain rate (0.4%/sec and 0.004%/sec) in simulated PWR environment with interrupting tests and the surface of specimens was observed. By the investigation of fatigue cracks growth, the effect of strain rate on crack growth rate was evaluated. From the results of tests, the followings were confirmed; ・Fatigu...
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Influence of Strain Rate on Fatigue Crack Growth in SUS316 under Reactor Coolant Environment

Numbers of nuclear power plants have been operating for more than 30 years and some of them exceeding 40 years in Japan. In these ageing plants, fatigue evaluation has a significant measure in assuring the plant reliability. The environmental fatigue in light water reactors, which was first recognized in the 1980's in Japan, has been drawing attention worldwide because it may cause remarkable effects on the life of important components. The Japanese nuclear industries developed the world's first pract...
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Environmental Fatigue Evaluation in PLM Activities of PWR plant

Numbers of nuclear power plants have been operating for more than 30 years and some of them exceeding 40 years in Japan. In these ageing plants, fatigue evaluation has a significant measure in assuring the plant reliability. The environmental fatigue in light water reactors, which was first recognized i n the 1980's in Japan, has been drawing attention worldwide because it may cause remarkable effects on the life of important components.. This paper int roduces a few examples of environmental fatigue evalu...
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Environmental Fatigue Evaluation in PLM Activities of PWR plant

The purpose of this study is to investigate environmental effects on SUS316 in different strain rate condition. The fatigue tests were conducted under different strain rate (0.4%/s and 0.004%/s) in simulated PWR environment with interrupting tests and the effect of strain rate on crack growth rate was evaluated by the observation of test specimen surface. From the results of investigation, the followings were confirmed; ・The effect of strain rate on crack growth rate is larger in 0.004%/s than 0.4%/s. ・The ...
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Environmental effect of stainless steel in PWR environment. (Investigation of Crack initiation and growth behavior by Replica Observation)

Japan is one of the countries with abundant active volcanos, and intensive research activities have been carried out for a long time on various volcanic phenomena including volcanic eruption. Furthermore, nationwide observation system of the volcanic activity has been established, and multiple countermeasures against volcanic disasters are being adopted. In nuclear power plant, the licensees are required to evaluate the impact of volcanic ash and develop the countermeasures based on the technical knowledge ...
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Nuclear Power Trials, Issue and Arguments No.3 Safety Assessment of Nuclear Power Plant under Volcanic Ash

A fatigue damage assessment procedure based on crack growth prediction was shown, in order to quantify the risk for failure of nuclear power plant components. First, crack initiation and growth behavior during low-cycle fatigue tests was reviewed and it was shown that the fatigue life could be estimated by predicting the crack growth without considering incubation period before the crack initiation. The change in crack size with the number of cycles was obtained by using the equivalent stress intensity...
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Fatigue Damage Assessment Procedure based on Crack Growth Prediction

Nuclear power plants (NPPs) are required to ensure safety in long term operation under aging degradation. The fatigue degradation is one of the major ageing phenomena and is evaluated to ensure safety by design fatigue curve obtained by the results of axial fatigue test. On the other hand, the stress that occurs in piping element such as elbow is not uniaxial but biaxial. For accurate evaluation of fatigue crack growth, it is required to confirm the effect of biaxial stress. In this study, membranous pressu...
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Study on the Behavior of Fatigue Crack Growth of Austenitic Stainless Steel Piping under biaxial Stress