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

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)

Suffered SCC (stress corrosion cracking) at the primary cooling system in 1980, the “Fugen” power station introduced the three preventive technologies immediately. After the upgrade of the plant, no SCC occurred during the operation period. We have inspected the actual structural materials of the “Fugen” power statio n on its decommissioning stage to evaluate effectiveness of SCC management technologies, which are combin ing material replacement, induction heating stress improvement (IHSI) to reduce the w...
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Evaluation of effectiveness of SCC prevention technologies after long term operation at the “Fugen” Power Station

Wall thinning of the steel piping of the secondary cooling system after long term operation using the serviced materials of “Fugen” Power Station has been investigated as a series of the evaluation of the validity and availability of the utilization of serviced materials on the research projects focused on the aging. Reliability of the wall thinning rate of the steel piping has been examined referring the previous inspection data. Besides, prediction of the wall thinning rate, rationalization of the m...
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Evaluation of wall thinning of the steel piping after long term operation at “Fugen” Power Station

In this study, the corrosion rate on the pipe wall downstream from an orifice was measured in order to validate the evaluation code for flow-accelerated corrosion (FAC). Three orifices with aperture ratios . = 0.62, 0.50, 0.41 was used in a test section with 50mm inner pipe diameter. The flow velocity was changed during the test to investigate the effect of mean cross-sectional flow velocity on the FAC rate. The water conditions were 150 degree centigrade, about 0.1ppb of dissolved oxygen concentration...
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FAC Rate Measurement downstream from an Orifice

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

To prevent degradation at Nuclear Power Plants (NPPs) by maintenance activity, fatigue evaluation should be improved to be more accurate. Studies of crack growth under equi-biaxial fatigue which is caused by thermal stress have been conducted for these purposes. Previous study shows that crack growth rate under equi-biaxial stress is faster than under uniaxial one. But the comparison is not quantitative. In this study, the difference of crack growth rate between equi-biaxial and uniaxial is confirmed q...
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Study on the Behavior of Fatigue Crack Growth of Austenitic Stainless Steel under Equi-biaxial Stress