Results of secondary side water regime modification in the paks nuclear power plant

The secondary side water chemistry in the Paks NPP was modified between 1997 and 2000. The modification was primarily justified by the risk of stress corrosion cracking of austenitic steel steam generator tubes because of the following: A great amount of iron corrosion products was deposited on heat transfer surfaces at the hot side of steam generators. In pores and cracks of deposits the local concentration of impurities of the water may reach levels causing SCC. Impurities causing the corrosion are chloride and sulfate ions and corrosion products of copper. In order to minilise their concentration in the SG water, their concentration must be reduced in the feedwater and steam system.