A model of irradiation damage in low alloy steel submerged arc welds has been developed by fitting test reactor data to physically reasonable mathematical equations. The model is underpinned by a substantial amount of microstructural data obtained using small angle neutron scattering, atom probe microscopy and other techniques. These data have been used qualitatively to show that the basic assumptions of the model are reasonable, and assessed quantitatively using the Russell and Brown modulus hardening model.
The model predicts hardness change in welds irradiated at high neutron dose rates as a function of irradiation dose, irradiation temperature and chemical composition. Correlations have been developed to enable Charpy or fracture toughness shift to be predicted from hardness change. In addition, a simple modification to the basic model allows estimation of damage at power reactor dose rates. This has enabled comparison with US surveillance programme data. Possible reasons for the observed differences in data and predictions are discussed. Plans to validate the model by testing material from a decommissioned RPV are outlined.