Separation of fission produced Ru-106 and (CS)-C-137 from aged uranium targets by sequential distillation and precipitation in nitrate media

Ruthenium-106 and Cs-137 have been separated from thermal-neutron irradiated UO3 targets aged for similar to 2.5 years by distillation and surface interactions in nitrate media of controlled chemical composition. After digestion of the aged targets with their aluminum wrapper in 2M NaOH solution, nitric acid was added to complete dissolution of the formed residue. The prepared fission product solution was separated from 1291 and 91.8\% Ru-106 by sequential distillation from 20\% and 40\% HNO3 solutions containing H2O2 and KMnO4, as oxidants, and by boiling for 4 and 2.5 hours, respectively. The recovery yield of Ru-106 collected in 0.1 M NaOH solution was similar to 68.2\% with a radionuclidic purity of >= 99.99\%. Thereafter, the fission product solution was brought to pH 9.5 by addition of NaOH solution to precipitate AI(OH)(3), MnO2, and Na2U2O7 which selectively retained the remaining fission products leaving, mainly, Cs-137 in the supernatant solution. The recovery yield of Cs-137 was >= 97.3\% with similar to 99.75\% radionuclidic purity. The gamma-ray emitter contaminants which could be detected and identified in the recovered Cs-137 solution, were similar to 0.25\% Cs-134 and similar to 1.4- 10(-3)\% (152,155) Eu.