Advanced fuel for fast breeder reactors produced by gelation methods

The paper outlines two decades of work at EIR covering the development of gelation processes for the production of mixed (U,Pu) nuclear fuels. The programme concentrated initially on the fabrication of uranium-plutonium carbides as an FBR advanced fuel. The requirements of smeared density (75-80% T.D.) permitted the use of 2-size fraction microspheres for vibro-filled fuel pins. The irradiation programme accompanying this work culminated in 1986 in the start of irradiation of 25 sphere-pac carbide fuel-pins in the US Fast Flux Test Facility, alongside US pellet carbide fuel. This test has currently exceeded 3% burn-up with a target of 9%. Associated with the FFTF programme was the development of extensive analytical and QA procedures to characterise the fuel and pins. Additional studies further examined the fuel stoichiometry and phase structure. Code development has also been carried out for the modelling of sphere-pac fuel behaviour. More recently, due to the revival of interest in Europe in mixed nitrides because of their carbide-like behaviour but with improved handling and reprocessing potential, EIR has started to examine a gelation route for the production of (U,Pu)N, based also on carbothermic reduction. Here EIR is collaborating with the CEA (DECPu Cadarache) to develop the gel fabrication process for microspheres or pellets followed by testing under fast reactor conditions. In a first stage the fuel make-up (O, C, N content) is being optimised. For pin fabrication similar techniques can be used as for carbide pins due to the similar requirements of smear density. (author). 12 refs, 5 figs, 3 tabs