On the French Project Developed in the 1980s for the Production of ⁹⁹Mo from the Fission of ²³⁵U

In 1985, the Commissariat à I’Energie Atomique (CEA), France, decided to set up an industrial unit at the Saclay Nuclear Research Center to produce fission ⁹⁹Mo and to supply this isotope to the ORIS Company, France, for medical applications. The CEA’s role in this project was to develop a brand-new process for ⁹⁹Mo production and to assume responsibility for the design and construction of the industrial plant. Production was based on 74 TBq (2 kCi) of ⁹⁹Mo per week, under particularly 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 ⁹⁹Mo on the world market, which made the French project uneconomic. The focus here is mainly on the research conducted at the time to define and to 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 acid medium, entailing the maintenance of radioiodine and radiotellurium, for safety reasons, in the form of I‾(AgI) and Te(0), respectively, allowing 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-butylacetohydroxamic acid, an extractant with exceptional affinity and selectivity for Mo(VI). The ⁹⁹Mo(VI) extraction cycles employ the extraction chromatographic mode.