Numerical Study Based on Local Approach of Fracture to Evaluate the Reference Temperature T0 From Mini-C(T) Geometry

Abstract In the context of the continued and safe operation of existing nuclear power plants and of long-term operation, mini-C(T) testing approach has been identified as a very promising approach as it allows (i) the direct evaluation of fracture toughness, (ii) the possibility to recover and reuse the available neutron irradiated materials by increasing the amount of fracture toughness data. While the applicability of mini-C(T) specimens to evaluate the reference temperature, T0, was experimentally extensively evaluated, showing the capacity of mini-C(T) to provide T0 values reasonably consistent with larger specimens, few studies were devoted to quantitatively evaluate the relative loss of constraint in this geometry regarding larger specimens. In this study, a probabilistic, micromechanical-based methodology, based on the Beremin model combined with 3D Finite Element simulations is applied in order to evaluate the effect of yield stress (YS) and strain hardening (n) on the loss of constraint in the mini-C(T) specimens and its relative deviation compared to CT-0.5T specimen. Numerical reference temperatures, T0num, are determined for a set of YS and n to assess the relative effect of these parameters for the two specimens. Finally, representative variation of YS and n for irradiated based RPV metals at high fluencies are considered in order to compare and discuss the numerical results of this study, with the experimental results available in the literature.