Impact of the Synthesis Process on Structure Properties for AFCI Fuel Candidates

Advanced Fuel Cycle Initiative research on transmutation fuels includes mono-nitride ceramic fuel forms, and consists of closely coordinated “hot” actinide and “cold” inert and surrogate fuels work. Matrix and surrogate materials work involves three major components: (1) fuel matrix synthesis and fabrication, (2) fuel performance, and (3) fuel materials modeling. The synthesis and fabrication component supports basic material studies, as well as actinide fuel fabrication work through fuel fabrication process development. Fuel performance studies are examining the tolerance of nitride-type fuel to heavy irradiation damage. The fuel materials simulation work involves both atomistic and continuum scale modeling employing first principles, molecular dynamics, and thermo-chemical calculations. This modeling work is closely integrated with fuel design and experimental work where it provides prediction of phase transformation and stability, reaction kinetics, radiation damage mechanism and tolerance, and fission product retention. Results for fuel fabrication and radiation tolerance studies based on the proposed ZrN fuel matrix material will be reviewed as well as experimental surrogate studies for volatilization and phase stability. The actinide fuel effort at LANL emphasizes synthesis and fabrication of actinide-bearing nitride fuel pellets. These pellets are designed to be inserted into the Advanced Test Reactor and contain varying amounts of Pu, Am, Cm, and Np. Presently, fuel materials simulation work which involves atomistic and continuum scale modeling, molecular dynamics, and thermo-chemical calculations are based on a theoretical understanding of crystal structure and microstructure of inert matrix fuels. This task’s contribution is to provide real structural data on surrogate and radioactive fuels. Crystallographic properties are being determined and nano structures of oxide-based and nitride based fuels, as considered for next generation reactor fuels, are being imaged after applying different synthesis routes. The chemical behavior of the ceramics under repository, reprocessing, and reactor conditions will be examined. Two fully equipped sample preparation laboratories can be taken advantage of, one for the preparation of surrogate fuel, and one for the preparation of radioactive fuel specimens