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

Air-conditioning duct is difficult to predict the date to occur of corrosion such as affect the function. Therefore, the current conservation method is mostly corrective maintenance. Therefore, was used the test pieces of six types and ACM-sensor in order to solve the corrosion speed from corrosion environment and relationship of corrosion quantity of test pieces. In addition, was used the duct molded articles various in order to check the corrosion degree of when processed the duct. As a result, we we...
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Preventive maintenance plan of the air-conditioning duct using the ACM-sensor

Abstract: Preparation for DEC (design extension condition) is one of the lesson learned from Fukushima nuclear accident. From the structural point of view, it is needed to know the failure modes of the pipe structure to make adequate preparation against excessive seismic loading. But the failure modes under seismic loading are still not clear. Low cycle fatigue is one of the major failure modes observed at seismic experiments. Ratcheting is also observed at some other experiments. And collapse is assum...
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Failure modes investigation of pipe structure under excessive seismic loading

JRR-3(Japan Research Reactor No.3) is a light water moderated and cooled, heavy water reflected, pool type research reactor with maximum thermal power of 20MW. The reactor is the first domes tic research reactor in Japan, and first criticality was attained in 1962. The large scale modification of the reactor was carried out for the year 1985-1990. As the modified JRR-3 has been operated for 18 years, it is necessary to be maintained for keeping the safe and stable operation. The review of maintenance activ...
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Maintenance activities of instrumentation control device at JRR-3

The maintenance evaluation for research reactors has been obligated in Japan from 2004 as for power reactors. JAEA (Japan A tomic Energy Agency) has started to evaluate the maintenance for own research reactors on 2004. In this paper, we report th e present status of the maintenance for JRR-3(Japanese Research Reactor No.3), as well as the linear evaluation methods use d. It is found that a series of preventing maintenance task on equipment and building of the reactor is properly performed....
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Assessment of Preventing Maintenance on Japanese Research Reactor JRR-3

In order to study the influence of welding condition on the detectability of flaws in Ni based alloy by UT, we lding conditions, such as heat input, magnetic stirring and weaving were changed. Flaws in small heat input we ld joints was difficult to be detected because of the presence of high noise. On the contrary, welded joints m ade with large heat input and weaving showed lower noise and EDM notches in these joints were easily detected....
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The Influence of Welding Condition on Flaw Detectability by Ultrasonic Test in Ni Based alloy welds.

The effect of irradiation on slip band formation and growth and micro-crack initiation behavior under low cycle fatigue in SUS316L austenitic stainless steel was investigated using accelerator-based proton irradiation and a low cycle fatigue test at room tem perature in air. The micro-crack initiation was observed at slip band, grain boundary, twin boundary, and triple junction regardless of the total strain range and the proton irradiation. In unirradiated specimens, the micro-crack initiation life droppe...
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Fatigue Micro-crack Initiation Behavior and Effect of Irradiation Damage on Itin Austenitic Stainless Steel

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

Authors previously reported that magnetic data obtained by using Eddy current method and AC magnetization method showed correlation with the increase of susceptibility of the irradiation assisted stress corrosion cracking (IASCC) on neutron irradiated austenitic stainless alloy specimens. To discuss the mechanism of the correlation, microstructure observation was conducted on the irradiated specimen, and this result, magnetic the permalloy radiation induced phase (FeNimagnetic 3) formation phase form...
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Study on Magnetic Property Change on Neutron Irradiated Austenitic Stainless Steel

Authors previously reported leakage magnetic flux density measured by flux gate (FG) sensor seems to depend on irradiation assisted stress corrosion cracking (IASCC) susceptibility of neutron irradiated austenitic stainless steels. This study aimed to evaluate possibility to develop diagnostic method to detect symptom of IASCC by more practical methods such as Eddy current method and AC magnetization method. Magnetic properties of neutron irradiated specimens and mockup specimens were studied and dep...
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A Study of Correlativity between IASCC Susceptibility and Magnetic Property of Stainless Steel