Improved processes of molybdenum-99 production

The isolation of99Mo from fission material for use in the99Mo/99mTc generator for medical use

Molybdenum-99 is an important radionuclide which is used in nuclear medicine and a new method is presented for the isolation and purification of99Mo from fission material. The method was developed to suit the needs of the Nuclear Energy Corporation of South Africa (NECSA) and also because most other methods had been patented and could therefore not be used at NECSA. A uranium-aluminium alloy, cladded in aluminium, served as a target and the target was irradiated in a nuclear reactor for several days. After a cooling period, in order to let the short-lived radionuclides decay, the target material was dissolved in a sodium hydroxide solution. The radioactive krypton and xenon gases were collected on activated carbon and stored until both gases had decayed. Aluminium,99Mo,131I and the radionuclides of alkali-soluble elements in the sodium hydroxide solution were separated from the uranium and radionuclides of the alkaline-insoluble elements by filtration. The radionuclides of molybdenum and iodine were separated by anion exchange chromatography, in alkaline medium, from the bulk aluminium and radionuclides of other elements, such as barium, strontium and tellurium.99Mo was selectively eluted with a slightly alkaline lithium sulphate solution, leaving the iodine radionuclides on the resin. The99Mo eluant was acidified with oxalic acid and nitric acid and99Mo separated from the remaining aluminium and other radionuclides by anion exchange chromatography, in acid medium. After elution of99Mo, again with a slightly alkaline lithium sulphate solution, the eluant was acidified with nitric acid,99Mo concentrated on a chelating resin column and finally eluted with ammonia and evaporated to obtain99MoO3which was then dissolved in diluted sodium hydroxide solution. The purity of the final product was within the specifications of the British and European Pharmacopoiea and no further purification steps, such as sublimation, were required.