Observation and measurement of erosion-corrosion in nuclear plants influence of chemical conditioning

The erosion-corrosion caused by wet steam leads to considerable damage of certain components of the thermal cycle and, the metallic oxides which are formed are carried by the circulating fluid and form deposits particularly on heat exchangers. This paper describes the measurements and the observations techniques that were used. The experimental data permits to quantify the material resistance as well as the transportation of oxydes during the successive periodes during which a modification of both the conception and the material were introduced. The analysis of trace quantities of Fe, Cr, Ni, CO... permit to determine the attack of various materials as well as the transportation of the respective oxides. The analysis of the circulating fluid and the measurements of the respective quantities of deposits allows to evaluate the calculations of transport, deposit and oxides removal. The erosion-corrosion phenomenon is dependent upon the environment. A modification of the conditioning (higher pH in PWR, use of oxidizing agents in BWR) permits only a limited reduction of erosion-corrosion and may even present some disadvantages