Process for recovering molybdenum-99 from a matrix containing neutron irradiated fissionable materials and fission products

摘要

Process for recovering molybdenum-99 from a matrix which has been irradiated with neutrons and contains fissionable materials and fission products, wherein the matrix is decomposed in an aqueous alkali hydroxide solution and the molybdenum-99 and part of the fission products are dissolved, the solution containing the molybdenum-99 is separated from a residue of particles containing at least actinides and lanthanides and is treated with thiocyanate ions to form a molybdenum complex. In the process, the alkali solution containing molybdenum in the form of molybdate (MoO4--) is conditioned with an iodine reduction agent. Mineral acid is added to the alkali solution. The molybdenum contained in the acidified solution is reduced to form three-valent molybdenum Mo(III) and the Mo(III) is complexed with SCN- ions to form [Mo (SCN)6]3- ions. The acid solution which contains [Mo (SCN)6]3- ions and contaminants is brought into contact with previously conditioned di-sec butyl ether (organic phase). The molybdenum thiocyanate complex ions are selectively extracted from the aqueous phase into the organic phase whereby the contaminants remain practically completely in the aqueous phase. The organic phase which is now charged with the [Mo(SCN)6]3- ions is separated from the molybdenum free solution. The separated organic phase is washed with diluted mineral acid in a concentration in the range from 0.001 to 0.1 Mol/l in a quantity corresponding approximately to the volume of the organic phase. The molybdenum is re-extracted with mineral acid in a concentration in the range from 5 Mol/l to 11 Mol/l from the washed organic phase into an aqueous phase.