b'Development of Accident Tolerant Oxide FuelGrain Growth Kinetic ModelsPrincipal Investigator: Tashiema L UlrichTeam Members/ Collaborators: David M Frazer, Joshua T. White and Tarik A. Saleh Averaged grain size of 36.415.1 m have being attained from sintering in CO 2gas for 24 hours, which is comparable to grain sizes that are achieved by commercial processes.F or the last six decades, industryProject Description:research teams have demon- For the last 50 years there have been strated that the addition of oxideongoing efforts to understand how dopants to UO 2fuel during fabricationdopants affect fuel properties such as provides significant improvement tothermal diffusivity, fission gas release, the microstructural properties, specifi- and creep strength; however, it is cally a fivefold increase of the grainchallenging to decouple the effects of size [1-2]. Enhanced grain sizes havedopants from effects of large grain size. been shown to improve fission gasDecades of experience with UO 2fuel release (FGR) within the fuel rodlet,have yielded a wealth of information as well as affect creep and hardnessregarding the microstructural evolu-of the fuel pellets. The Advancedtion and sintering kinetics of undoped Fuels Campaign (AFC) is supportingUO 2providing critical insight into research that seeks to understand thethe atmospheres and temperatures role that dopants have on FGR, whichrequired to yield dense pellets. Unfor-is important for extending the life- tunately, many of these studies provide cycle of the fuel. It has been suggestedinconsistent or incomplete results that dopants increase not only theon the grain sizes of sintered pellets, grain size, but also enhance fissionwhich requires further investigations. gas diffusion, potentially negating theThis project will expand on previous benefits of large grains [3]. Since largesintering kinetics studies to provide grain size UO 2has predominantlyinsight into controlling sintering been obtained by the addition ofdwell time, sintering atmosphere dopants, this study has been proposedand stoichiometry of UO 2to emulate to grow large grain sized UO 2withoutmicrostructures from Accident Tolerant the aid of dopants allowing for studiesFuel (ATF)-derived Cr and/or Al which decouple the grain size effectdoped fuel commercially produced by on FGR in future irradiation studies. industry. Successful completion of the project would allow for a consistent 54 2020|AFC ACCOMPLISHMENTS'