[en] Radioactive wastes generated from the Post-Irradiation Examination Facility (PIEF) and research laboratories in KAERI are to be treated at the Radioactive Waste Treatment Facility(RWTF). Low and intermediate liquid wastes are transformed into a solidified from after volume reduction by evaporation. The condensate obtained from the evaporator is generally very low level liquid radioactive waste(VLAW), and was planned to be discharged to the environment after dilution. Later this original plan was modified by introducing Zero Release concept, further treatment of the VLAW with non-boiling forced draft evaporator system (NBFE). The existing theoretical approach was made use of to determine the facility size for the evaporation capacity and batch type experiments were performed to verify the evaporation rate. Radioisotope used for the simulated liquid waste was Cs-137 with the concentration range of 1xE-3 - 1xE-4μCi/cc. Analysis of the samples obtained during the operation was done by the Multi-Channel Analyzer. Performance test results showed that the evaporation atmospheric conditions varied 0.05 - 0.5 1/h.m² and the DF was over 1xE4. Environmental assessment using QAD-CG program showed that exposure dose rate for an operator would be reached about 0.035 mrem/hr which was nearly negligible and no or extremely low radioactivity in the air stream discharged(1xE-15 μCi/cc air discharged). (Author)