SMILE Project — The Effect of Warm Pre-Stress in RPV Assessment: Synthesis of Experimental Results and Analyses

Abstract

Within framework of 5th EC European SMILE project, some R&D actions have been conducted to demonstrate, to model and to validate the beneficial warm pre-stress (WPS) effect regarding the risk of brittle failure in a RPV assessment. An important experimental work has been conducted including classical WPS type experiments on CT specimens on usual RPV steels, and one PTS type transient on a large cracked cylinder. All experimental results confirm the beneficial effect of warm pre-stress, with a significant increase of the materials resistance regarding the risk of brittle failure. The experiments have been analyzed using fracture mechanics, including both engineering methods (Chell, Haigh, Wallin) and more refined analyses based on local approach to fracture (‘modified Beremin’ model). Following a short description of WPS concept, the paper summarizes the main experimental results and presents a synthesis of mechanical analyses involving engineering approaches and numerical analyses.

Current understanding of radiation-induced degradation in light water reactor structural materials

“…This is to establish a reasonable margin for PTS evaluation since WPS is expected to increase fracture toughness at low temperatures. A sample of fracture toughness data have been reported after various stresstemperature procedures, for example, load, cooling and fracture, and load, unload, cooling and fracture [167,168]. It was confirmed that WPS effects appear in unirradiated pressure vessel steels.…”