ATLAS+ is a four year, €7M Horizon 2020 project aimed at developing and validating advanced structural integrity assessment methodologies for non-RPV primary circuit pressure boundary components. Two thin-walled welded pipe mock-ups are being manufactured as part of ATLAS+. The proposed experiments on the welded mock-ups have three objectives. First, they serve as an important step in the validation of potentially challenging weld residual stress simulations for thin walled pipes. Second, the measurements are required to fill in gaps in the current population of pipe girth weld mock-ups required to train Artificial Neural Networks for prediction of residual stresses. Third, the measurements are aimed at studying, for the first time, the relaxation of residual stresses during cold creep in stainless steel welded structures simulating the in-service conditions of future nuclear reactors.