APPLICATION OF NI-PLATING TO PREVENT STEAM GENERATOR TUBING FROM SCC IN NUCLEAR POWER PLANTS

摘要

In order to prevent steam generator tubing from stress corrosion cracking occurring in the expansion transition region around the top of a tubesheet in nuclear power plants (NPPs), the Ni-plating technique in a sulfamate solution was studied to make sure if Ni-plated and subsequently expanded Inconel 600 tube can be compatible with SCC in the operating conditions of pressurized water reactor (PWR) NPPs. Ni-plating from both ends of steam generator tubes up to above the regions where tube expansion will be done was carried out before manufacturing the steam generators, and subsequently the Ni-plated regions of the tubes are expanded by using a hydraulic expansion method. Afterward, the integrity of the expanded Ni-plated layers were examined and their susceptibility to SCC was investigated using C-ring specimens in the simulated secondary side operating conditions. According to the test results, Ni-plated Alloy 600 HTMA tubes showed high resistance to SCC in the test condition and was confirmed to be used to prevent the tubes from stress corrosion cracking under operating conditions of NPPs.