Fracture toughness characterization of irradiated, low upper shelf welds

A data base of J − R curve trends is being established for irradiated, light-water reactor pressure vessel steels of low upper shelf toughness. R-curve trends have been developed for several welds made with Linde 80 flux and containing a high copper impurity which enhances the sensitivity to irradiation embrittlement. Tests were conducted using compact toughness specimens of 12.5 mm to 100 mm thickness. These data provide the materials properties necessary for a tearing instability analysis of postulated accident conditions in certain commercial power reactors. Irradiation decreased the level of the R curve significantly in most cases. Furthermore, the average value of tearing modulus (T_avg) was a more discriminating indicator of toughness degradation than the crack initiation toughness (J_Ic). Temperature-dependent correlations between the R-curve parameters (J_Ic, T_avg) and Charpy-V (C_v) upper shelf energy have been suggested here and in other programs. This finding could enhance the significance of C_v reactor surveillance data with respect to structural integrity. However, J_Ic and T_avg have demonstrated an inverse relationship with temperature which is not reflected in C_v upper shelf energy and this must be taken into account in the development of correlations.