Evaporation of low-activity-level liquid waste at Tokai Reprocessing Plant, 1

The operation of Tokai reprocessing plant started in 1977. The determination of the decontamination factors (DF) of the evaporators for low activity level liquid waste (LALW) has been made through the operation. This paper deals with the examination of the first evaporator located at the LALW treatment plant. The operational principle and condition of the evaporator system are briefly explained. The effects of wire-mesh demisters and liquid properties on the decontamination factor were examined in this study. The results are summarized as follows: (1) The DF decreased with the increasing vapor mass velocity on account of entrainment. (2) The DF was able to be improved by using wire-mesh demisters when the vapor mass velocity was less than 2,500 kg/m2h. Practically, the most suitable vapor velocity for the evaporator was around 2,000 kg/m2h. (3) The DF in the evaporator for 137Cs, 144Ce, 90Sr and 106Ru was between 103 and 104. Regarding 106Ru, the DF in acid evaporation was less than that in alkaline evaporation. (Aoki, K.)