Quantification of Transferring and Adhering for Pd, Mo, Te, Sb, Ru, Re, Cs and I During the Evaporation Under Vacuum and at Atmospheric Pressure

In order to modify current nuclear fuel reprocessing plants on the basis of a more sophisticated, economical, and safer nuclear waste recycling system, the production of low-level radioactive wastes must be reduced and the recycling of wastes must become more efficient. To simulate liquid waste recycling operations, evaporators under vacuum and at atmospheric pressure were used to determine adhering and transferring rates for Pd, Mo, Te, Sb, Ru, Re, Cs and I in the nitric acid and sodium nitrate solutions. In the evaporation from the HNO₃ and NaNO₃ solutions containing precipitate PdI₂, the percentage values for materials adhering on the inside of lid at vacuum pressure were 0.01 ∼ 0.1%/m², however at atmospheric pressure the values were 0.001 ∼ 0.01%/m². Adhering percentage values on the condenser were 0.0001 ∼ 0.001%/m² for the vacuum and atmospheric pressure systems. The transferred percentages into the distillate for Pd, Mo, Te, Sb, Ru, Re, and Cs were 0.0001 ∼ 0.001% in the HNO₃ and NaNO₃ solutions for the vacuum and atmospheric pressure systems, and those of I were about 10% for HNO₃ system at atmospheric pressure, 2∼7% for HNO₃ system under vacuum, 0.01∼0.1% for NaNO₃ system under vacuum. Reducing rates for the treated solution were one third of feeding solutions in the evaporation under vacuum and at atmospheric pressure.