Pressurizer nozzle replacements

Convinced of the generic nature of the problem, EDF decided to replace all of the Inconel 600 nozzles in their 1300 MWe pressure vessels. The replacements were fabricated from austenitic stainless steel which has a good record of operating without corrosion on its SS nozzles and welds and has been used on many 900 MWe units, both in France and abroad. Two different approaches were used to replace the nozzles, internal access after decontamination and external replacement. The internal access approach was used for the vapor space section of the pressure vessels and external replacement was conducted in the liquid solution section of the vessels. A general overview of the replacement process is given which includes typical defects found and specific problems which had to be addressed such as decontamination and personnel exposure rates and customizing automatic welding equipment. 16 figs., 2 tabs