A full-sized section of 304-stainless steel pipe with a non-stress relieved girth-butt weld has been obtained from a Pressurised Water Reactor. This project will accurately map the residual stress profile across the weld, using neutron diffraction to penetrate the stainless steel to a sufficient depth with high resolution, enabling accurate strain measurements through thethickness of the pipe to be obtained. This will be complemented with deep hole drilling measurements of the residual stress profile across the weldment. The measured residual stresses will form a key component of understanding how combined primary and residual stresses influence the fracture of an actual PWR pipe weld. This data will be used to calibrate a Finite Element Analysis model, to enable future assessments of weld residual stress in pipes to be simulated numerically with a good degree of confidence.