Szilard-Chalmers reaction of molybdenum hexacarbonyl target for the preparation of radioisotopes 99Mo

The preparation of 99Mo with activity suitable for 99Mo-sup(99m)Tc generator has been thoroughly studied by the Szilard-Chalmers reaction. Molybdenum hexacarbonyl was used as the target material while as the solvent chloroform was used. The recoilled 99Mo was extracted into water. In order to obtain a high yield the use of several concentrations of NaOH and NH4OH in aqueous solution has been used. The yield of molybdenum was 6.86, 15.56 and 18.75% in respectively H2O, 4N NH4OH, 3N NaOH as aqueous phase. Reducing the air pressure on the targets until 10-4 Torr will increase the yield to 50% with 3N NaOH as aqueous phase. The effect of the time of irradiation on the specific activity of 99Mo has also been studied, in which 60 hours irradiation will produce a specific activity of 91 MBq/mg*. The molybdenum concentration in the aqueous phase was determined by spectrophotometry from its complex formation with thiocyanide ion, at a wave length of 462 nm. The enrichment factor was determined through (n,γ) reaction by irradiation of MoO3 targets with thermal neutron. The enrichment factor of 99Mo was 537 after irradiation of 60 hours. (author)