ON THE FRENCH PROJECT DEVELOPED IN THE 1980S FOR THE PRODUCTION OF MO-99 FROM THE FISSION OF U-235

In 1985, the Commissariat a I'Energie Atomique (CEA), France, decided to set up an industrial unit at the Saclay Nuclear Research Center to produce fission Mo-99 and to supply this isotope to the ORIS Company, France, for medical applications. The CEA's role in this project was t o develop a brand-new process for Mo-99 production and to assume respo nsibility for the design and construction of the industrial plant. Pro duction was based on 74 TBq (2 kCi) of Mo-99 per week, under particula rly severe constraints to protect the environment and the workers. The production unit, run in a semiautomatic mode, was built at Saclay in 1987 and cold tested from 1987 to 1989. The unit was never upgraded to active experiments because of the sudden drop in the price of Mo-99 o n the world market, which made the French project uneconomic. The focu s here is mainly on the research conducted at the time to define and t o validate the entire fission molybdenum chemical process. The process flowchart incorporates two original features. First, in the head-end of the process, the irradiated targets are dissolved in a sulfuric aci d medium, entailing the maintenance of radioiodine and radiotellurium, for safety reasons, in the form of I-(AgI) and Te(0), respectively, a llowing their easy removal as solids from the dissolution liquors and their subsequent storage for radioactive decay. Second, in the core of the process, the molybdenum is purified by extraction with tri-n-buty lacetohydroxamic acid, an extractant with exceptional affinity and sel ectivity for Mo(VI). The Mo-99(VI) extraction cycles employ the extrac tion chromatographic mode.