Stress corrosion cracking is an important degradation mechanism that is threatening the structural integrity of pressurised water reactors throughout the world. Dissimilar weld mock-up has been made using a corrosion resistant weld filler (Alloy 52) with a narrow gap weld design to reduce residual stresses. It is essential to quantify the residual stresses in this proposed weldment design. The residual stress measurements by neutron diffraction strongly depend on the measurements of the appropriate reference sample. The proposers believe that if stress-free measurements are made on new material extracted from the heat treated pipe, this will produce the first high quality neutron diffraction measurements made in a dissimilar metal pipe weld of this kind.