REMOVAL OF DEPOSITS CONTAINING IRON-OXIDE FROM STEAM-GENERATORS OF PRESSURIZED WATER-REACTORS

After describing formation and composition of deposits on heated pipe wall surfaces, the removal of the deposits is discussed. The inorganic and organic acids usually applied act primarily by their hydrogen ions. Reactions of anions are decisive if complexing agents like NTE or EDTE are used in neutral or alkaline solutions. Generally, the base metal is but slightly attacked, even without additional inhibitors. However, temperatures above 150-degrees-C, relatively high concentrations of the agents, intensive mixing, and reducing conditions are needed for quick dissolving of the oxides.