Transgranular fracture of Fast Reactor irradiated stainless steel

An understanding of the fracture of Fast Reactor fuel pin cladding can provide a basis for predicting the failure of fuel pins in normal reactor operation, or in assessing the severity of hypothetical accidents. Mechanistic modelling of the various failure modes is the most promising means of gaining such an understanding and we present here theories describing the transgranular mechanical fracture mode of 20% cold-worked AISI 316 steel. This is characterised by plastic yield deformation when the stress exceeds a yield stress. The main part of the development deals with the evolution of the yield stress under irradiation at high temperature. We also consider the evolution of the constitutive relations, especially the effect of cladding porosity on the ductility, and find that neutron-induced void swelling may be responsible for low failure strains in some circumstances. (orig.)