Welding simulations have been employed in nuclear power industrial applications for over 20 years to predict manufacturing residual stresses in critical plant components. Tensile residual stresses can have a detrimental effect, exasperating in-service degradation mechanisms such as fatigue, fracture and environmentally assisted cracking in a corrosive water environment. Simple conservative assumptions, such as yield magnitude through-wall tensile Residual Stress (RS), can be very penalizing in evaluating defect tolerance margins. More realistic and less conservative RS distributions can be predicted by weld models. This has enabled plant life extensions to be justified, thereby saving substantial costs in plant outages, inspection, maintenance and repairs. It is important that weld modelling methods are experimentally validated, so that Finite Element Analysis (FEA) predictions of residual stress magnitudes and distributions can be used with greater confidence.