High Thermo-Separation Efficiency of super( 99m)Tc from Molten super( 100)MoO sub( 3) Samples by Repeated Milking Tests

High thermo-separation efficiencies of about 90 and 70% have been obtained for the first time for 99mTc from molten MoO3 samples containing 99Mo with thicknesses of 4.0 and 8.5 mm, respectively, by repeated milking tests. 99Mo was produced with100Mo(n,2n)99Mo by using neutrons from 3H(d,n)4He. The thermo-separation efficiency was determined by measuring the 141 keV gamma -ray yield of 99mTc within the molten MoO3 samples with a radiation detector as a function of the furnace temperature and time. The diffusion coefficients of 99mTc in the molten MoO3 samples were estimated in order to help understand the high thermo-separation efficiency. The present result solves a long-standing problem of decreasing the separation efficiency of 99mTc from MoO3while increasing the sample mass or repeating sublimation in thermo-separation, and will bring a major breakthrough to obtain high-quality 99mTc from MoO3 irradiated by accelerator-neutrons (protons) or reactor-neutrons.