Effects of chemical compounds on the stress corrosion cracking of steam generator tubing materials in a caustic solution

Some nuclear power plants have degradation problems of their steam generators, associated with caustic SCC or lead-induced SCC in a caustic environment. The electrochemical corrosion potential is measured for a mill-annealed Alloy 600 specimen in a caustic solution with Cu oxide if it is present in the sludge. The effect of the applied potential on SCC is tested using a slow strain rate test unit for the same tube material in a caustic solution containing lead species. All kinds of steam generator tubing materials used for nuclear power plants in operation and under construction in Korea are tested with modified reverse u-bend specimens in a caustic solution containing lead oxide and their crack morphology is investigated. In addition, the effects of the inhibitors such as TiO2 and CeB6 on SCC are tested for these tubing materials in a caustic solution.