Abstract: In view of an obvious decline in processing capacity of radioactive liquid waste evaporator in a short period of time, the method of Langelier Saturation Index (LSI) was used to judge the scaling and corrosion tendency in the evaporator. Effects of pH, evaporation temperature, Ca²⁺ concentration and stock solution flow rate on evaporation scaling rate were analyzed. The results show that the evaporation liquid has the tendency of scaling and corrosion. Variations of pH and other factors increase the scaling rate of the evaporator. After scaling, the evaporation intensity of the evaporator decreases by 75%. An immersion acid descaling scheme for radioactive waste liquid evaporator was designed, based on commonly used descaling methods for civil evaporators and combining with safety requirements of nuclear industry evaporators. It has been verified by experiments that this scheme is safe and feasible. The descaling effect is obvious, and the processing capacity of the evaporator has restored to its original design value of 0.6 m³/h after descaling.

Key words: evaporator, scaling analysis, immersion, acidic descaling, verification