Some welds made with Linde 80 flux and containing a high copper impurity level have exhibited postirradiation Charpy upper-shelf energy levels below 68 J (50 ft · lb). The J-R curve behavior of seven such low upper-shelf welds has been characterized in the ductile upper-shelf regime in both the preirradiation and the postirradiation conditions with fluences of ~1 × 10¹⁹ neutrons (n)/cm² (E > 1 MeV). With the single specimen compliance (SSC) technique, these J-R curves were determined from compact toughness (CT) specimens ranging from 12.7 to 101.6-mm thick, over a temperature range of 75°C to 288°C.

For these reactor vessel steels exhibiting low upper-shelf energy levels, the J-R curves were shown to follow a power-law relationship for small crack extensions, that is, less than 2 mm. In some cases, a possible size dependence of the J-R curve has been seen, but the results are inconclusive on this point.

Correlations between J-R curve parameters (J_Ic and average value of tearing modulus, T_avg) and C_v upper-shelf energy have been suggested at 200°C. These findings 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 that is not reflected by the C_v upper-shelf trend. Therefore, correlations between C_v energy and J-R curve must be adjusted to account for temperature.