Stress corrosion cracking is an important degradation mechanism that is threatening the structural integrity of pressurised water reactors throughout the world. AREVA has designed and made a dissimilar weld mock-up using a new 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. Some neutron diffraction measurements have been carried out already on the mock-up at the JRC but the results showed a lot of scatter. The aim of the present experiment is to use the more powerful capability of the ENGIN-X diffractometer at ISIS to obtain more reliable measurements and advance scientific methods for measuring residual stresses in highly textured weldments.