Recovery of molybdenum precursor material in the cyclotron-based technetium-99m production cycle

Abstract

A closed-loop technology aiming at recycling the highly100 Mo-enriched molybdenum target material has been developed in the framework of the international research efforts on the alternative, cyclotron-based99m Tc radionuclide production. The main procedure steps include (i)100 Mo-based target manufacturing; (ii) irradiation under proton beam; (iii) dissolution of100 Mo layer containing9× Tc radionuclides (produced by opened nuclear reaction routes) in concentrated H2 O2 solution; and (iv) Mo/Tc separation by the developed radiochemical module, from which the original100 Mo comes as the “waste” alkaline aqueous fraction. Conversion of the residual100 Mo molybdates in this fraction into molybdic acids and MoO3 has been pursued by refluxing in excess of HNO3. After evaporation of the solvent to dryness, the molybdic acids and MoO3 may be isolated from NaNO3 by exploiting their different solubility in water. When dried in vacuum at 40◦ C, the combined aqueous fractions provided MoO3 as a white powder. In the last recovery step MoO3 has been reduced using a temperature-controlled reactor under hydrogen overpressure. An overall recovery yield of ~90% has been established.