A study on the evaporation of cadmium for the recovery of actinides from a liquid cathode

The distillation behaviour of cadmium at a reduced pressure was investigated to develop an actinide recovery process from a liquid cadmium cathode in a laboratory scale cadmium distiller. The apparent evaporation rate of cadmium increased with an increasing temperature whereas the rate decreased with an increasing vacuum pressure. The evaporation rate of cadmium varied within 9.7-40 g/cm2/h in the temperature range of 500-650 deg C and pressure range of 0.5-10 Torr (0.0667-1.33 kPa). The theoretical values calculated by the Hertz-Langmuir relation were much higher than experimentally measured values. The deviation was compensated by an evaporation coefficient (α) obtained empirically. About 0.02-0.20 wt% of residue was left in the crucible after distillation and found to be CdO. It could be concluded that the temperature range of 500-650 deg C is favourable for the cadmium distillation process if residual eutectic salt does not exist in the cadmium alloy surface. (author)