Metal oxide deposits can form on heat exchange surfaces or structural components (tube-sheets, tube support plates) in PWR steam generators. They result in a reduction of the performance of the generator and corrosion in zones where the impurities concentrate. In order to clean steam generators, mechanical cleaning, used for the tube-sheet, has to be developed to become more efficient. Chemical cleaning enables the entire steam generator to be cleaned, including the tube-to-tube support plate crevices. Regardless of the design and materials used in steam generators in the future, it will always be necessary to keep them clan. This may be achieved by a preventive chemical cleaning combined with a mechanical technique.