Welding experience of the reactor pressure vessel for Tokai nuclear power station

The first nuclear power station in Japan is being constructed at Tokai-mura in Ibaraki Prefecture. The station is an advanced Calder Hall type. The electrical output is 166 MW. The pressure vessel was fabricated using 80 mm ($\text{3}\text{5}\text{32}\text{in.}$) and 92 mm ($\text{3}\text{5}\text{8}\text{in.}$) thick aluminium killed steel made in Japan.

Each part of pressure vessel, bottom cap, belt 1, 2, 3, 4 and top cap were prefabricated, then lifted into the reactor building and assembled. Welding of pressure vessel was carried out by 75 skilled welders of Fuji Electric Co., Ltd.

Single sided welding of skirt to skirt forging, C/D nozzle to shell welding and C/D standpipe to nozzle welding were very difficult, particularly to get good penetration and to keep accurate positioning and verticality. As a result of good technical control, hard training of welders, sufficient preparations and preliminary experiments, this difficult work was completed successfully and smoothly to programme.