UK power plants are following the worldwide trends in the power generating industry, in line with demands for increases in the efficiency of existing power plants and for reductions in greenhouse gas emissions. Investigation of new materials and their weldability are vital. In this research we propose modification of welding processes and PWHT for P91 steel which offers the opportunity to define more economical and beneficial practice that could reduce the cost of fabricating reliable welds. There are three main objectives of the present proposal: (1) to determine the RS in the P91 pipe in the as-welded condition, as well as after successful PWHT; (2) cross correlation of the ND results with the contour method; finally, (3) the results will be compared with current structural integrity assessment procedures.