Thermal Aging Effect on Environmental Fatigue Life of CF8M Cast Stainless Steel at Strain Rate 0.04%/s under PWR Operating Condition

In order to see the effect of thermal aging on environmental fatigue life of CF8M cast austenific stainless steel (CASS), low-cycle environmental fatigue tests of thermally aged CF8M CASS at the condition of fatigue strain rate 0.04%/s were conducted at the operating condition, 15MPa, 315 degrees C of pressurized water reactor (PWR) environment. Test results of low cycle fatigue life tests for thermally aged specimens simulating 60 operating years were compared with ones of un-aged CF8M CASS in room temperature air and PWR operating conditions to see the effect of the thermal aging on environmental fatigue life. This kind of experiment would be useful to verify the fatigue integrity of long-lived components and to predict plant safety of long term operation beyond design life because current approach of evaluating environmental fatigue is so conservative to apply it to the long-lived components in pressure boundary of nuclear power plants.