Reactor pressure vessel

Purpose: To reduce the weight of a nuclear reactor pressure vessel by reducing the plate thickness of the vessel using steel sheets having material characteristics of high strength and high toughness. Constitution: As the plate structure of a nuclear reactor pressure vessel, stainless steels are clad-welded on both sides of high tensile steels, for example, of 80 - 100 kg/mm2 class. Further, material of lower heat expansion coefficient than that of the matrix material is used to produce residual compression stresses both at the inner and the outer surfaces upon reactor operation to reduce the notch sensitivity. This can add compression stresses to the inner and outer surfaces of the plate to prevent the occurrence and development of crackings formed at the plate surface. Accordingly, it is possible to reduce the plate thickness of the pressure vessel and thereby reduce the weight thereof. (Takahashi, M.)