THERMAL AGEING OF CAST DUPLEX STAINLESS STEEL PRIMARY COMPONENTS. OVERVIEW OF THE RESEARCH PROGRAM CONDUCTED BY EDF

摘要

The integrity assessment of cast duplex stainless steel components from the primary circuit of the PWR units relies on several research and development studies :- The ageing surveillance programme on test ingots (cast at the same time as components) and on special products cast for studies has enabled us to develop prediction formulas of end-of-life toughness properties applicable to every component.- Tests on large-sized elbows containing analytical notches have shown their satisfactory behaviour even in severe situations (low toughness and high loadings).- The development of a numerical tool (called ASCOUF) aimed to easily perform 3-D calculations.- Tests on mock-ups containing casting defects have shown that the resistance of shrinkage cavities to fatigue and to ductile tearing is much higher than the resistance of the envelope notches that are considered in mechanical analyses.