System development of pure nickel plating process for RPV cladding repair

Electrolytic plating inside a damaged region does not induce deformation and hence a negligible residual stress, so a post heat treatment for a stress relief is not required, thus avoiding the associated heat affected zone. Especially, it has also been reported that Ni plating of a relatively higher deposition rate and a lower internal stress are obtained in a Ni sulfamate bath rather than Ni chloride and sulfate baths. This article aims to address how the plating process was established to create the test procedures and to discuss what factors should be taken into account in order to produce a uniform coating layer. - The carbon/low alloy steel of a RPV bottom region was exposed to primary water due to an accident of a thermal sleeve detachment of cladding layer. - The code case N-840 was approved by ASME for the application of pure nickel plating technology. - A device for plating was designed and test procedures were developed to establish the plating process. - Current distribution is most important, so a shielding basket was attached to the anode electrode to suppress the current density distribution at the edge of the plating layer.