Some examples of physical-chemical processes occurring in the water and steam of power stations

Unwanted impurities in water and steam cause serious problems in modern power plants. Substances highly soluble in hot water are particularly concerned: sodium hydroxide, sodium chloride and certain sodium phosphate salts and potassium salts. Hot water solutions of such compounds have vapor pressures lower than pure water at the same temperature and the boiling points are elevated so that concentrated liquid phases can coexist with superheated steam. The resulting phenomena and the damages caused by these impurities are reviewed: corrosion and failures of turbines, valves, heat exchangers, reheaters etc... in nuclear systems