Reliability of welding joints of pressurized light-water reactor vessels

Hydrogen content reduction in the pressure vessel inner lining was studied using 60 mm thick plates of CrMoV medium alloy steel. 25Cr/13Ni strip electrodes were used for surfacing the first layer while 19Cr/10Ni electrodes were used for all other layers. The overlays were annealed for 6 hours at 665 degC in order to determine the possibility of reducing the hydrogen content of the austenitic overlays. The heat treatment caused the formation of carburized zones between the overlay and the base metal, thus forming a suitable barrier against hydrogen diffusion from the overlay to the CrMoV steel. The zone was shown to positively affect the stabilization and deflection of crack propagation. The effects were also studied of phosphorus and sulfur microsegregation along grain boundaries. (M.D.). 7 refs