The fracture behaviour of low-alloy reactor pressurevessel (RPV) steels with different microstructures,chemical compositions and mechanical properties insimulated light water reactor environments was evaluatedby elastic plastic fracture mechanics tests. Moderate butclear environmental reduction of fracture initiationresistance occurred in RPV steels with high yield stress,high dynamic strain aging (DSA), environmentallyassistedcracking (EAC) and temper embrittlement (TE)susceptibilities. Failure occurred dominantly by stableductile transgranular tearing with micro-voidcoalescence in both air and high-temperature waterenvironments. Additional and varying amounts (a few %)of secondary cracking, macro-voids, quasi-cleavage andintergranular cracking were observed in hightemperaturewater environments. The environmentalreduction of fracture resistance is due to hydrogen andthe main reason for the moderate degradation effects isthe low hydrogen availability in high-temperature water.
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