Microstructure in a cast stainless steel used for a PLR pump casing cover in a BWR was investigated by atom probe tomography and nanoindentation testing. Ferrite phase decomposition and G-phase precipitation were no t observed in the as-received PLRP casing cover. Thermal aging and solution treatment were carried out on the as-received PLRP casing cover and an unused model alloy of cast stainless steel. The ferrite phase decomp osition and G-phase precipitates in the thermal aged model alloy disappeared af...
英字タイトル:
Microstructure in cast stainless steel used for long-term in BWR environment

Aging management technical evaluation is required for LWRs every 10 years at and after 30 years operation in Japan. Thermal aging evaluation of austenitic cast stainless steel components is one of the items of aging evaluation. Technical basis of thermal aging evaluation for BWR components such as thermal aging behavior of cast stainless steel used in Japanese BWRs, applicability of thermal aging prediction models and basic way of integrity evaluation of the components are described in this paper....
英字タイトル:
Technical basis of thermal aging evaluation of stainless steel cast steel components in BWR

Fracture toughness tests and atom probe tomography were conducted to evaluate the effect of thermal aging on the fracture toughness and the microstructural evolution in ferrite phase of shielded metal arc weld (SMAW) and gas tungsten arc weld (GTAW) of type 316L stainless steels. The resistance to ductile crack extension of aged welds was lower than that of unaged welds. For the GTAW the effect of aging temperature on the reduction rate of the fracture toughness, which may be due to relatively high ferrite ...
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Study on Thermal Aging of Stainless Steel Weld Metals

Tensile test, fracture toughness test, and stress corrosion cracking (SCC) test were conducted in order to evaluate the effect of thermal aging on the mechanical properties and SCC crack growth rate of shielded metal arc weld (SMAW) and gas tungsten arc weld (GTAW) of type 316L stainless steel. Thermal aging at 350 oC induced a moderate increase of ultimate tensile strength in both the welds, and the value of GTAW was higher than that of SMAW. The resistance to ductile crack extension of aged welds was lowe...
英字タイトル:
CRIEPI Activities for Evaluation of Thermally Aged Stainless Steel Weld Metals

After Fukushima-Daiichi accident, nuclear power plants are highly requested to enhance safety against severe accident. It is important to prevent fatigue failure for operating nuclear power plants, especially pressure boundary of compon ts to ensure safety. This paper studies the failure database of nuclear power plant in Japan (NUCIA) and extracts the events caused by fatigue failure. Fatigue failure can be classified according to fatigue mechanism such as mechanical vibration, fluid vibration, high-cycl...
英字タイトル:
Study of fatigue failures to improve safety based on the analyses of failure database in Japanese nuclear power plant

The water of Suppression pool at severe accident has become a hot, high chloride ion concentration and strong alkaline because of exhaust of the reactor heat, the melted cable, and pH controller. The equipment using the water has wetted part made stainless, therefore there is a possibility that SCC because of chloride ion occurs this wetted part. However, alkaline environment may reduce a possibility the SCC although poor knowledge. As such we examined the effect of structural material in a hot, high chlori...
英字タイトル:
Effect assessment of structural material in a hot, high chloride ion concentration, and strong alkaline environment

Aging management technical evaluation (AMTE) is required for LWRs every 10 years at and after 30 years operation in Japan. Result of the AMTE is put into plan of a long-term maintenance program of each plant. Methods for implementation of aging management measures were set forth in “Code on Implementation and Review of Nuclear Power Plant Ageing Management Programs” of Atomic Energy Society of Japan. Technical basis of material aging evaluations in the standard are described in this paper....
英字タイトル:
Technical Basis of Material Aging Evaluation in the Aging Management Technical Evaluation