b'Evaluation of Metallic Fuel Additives in U Fuel (U-Sn and U-Pd)Principal Investigator: Michael T. Benson, INLTeam Members/ Collaborators: Yi Xie and James King (INL)The current work is a continuation of that work, using U as the fuel, without Zr. The objective of this work is to characterize the microstructure of the metallic fuels with these additives, and to evaluate performance in out-of-pile diffusion couple tests.An additive that effectively controls FCCI will help the Department of Energy (DOE) meet its objectives of a safe, reli-able, and economic reactor by signifi-Figure 1. SEM backscatterF cantly improving fuel performance. uel-cladding chemical interaction images of U fuels with Sn(FCCI) occurs when the nuclearBy preventing FCCI due to the fission additive. a.) U-Sn, b.) U-Sn-Ln. fuel or fission products react withproduct lanthanides, cladding ruptures the cladding material. A major cause ofwill be prevented, improving fuel safety FCCI in U-based fuels during irradiationand reliability, and higher fuel burn-up is fission product lanthanides (Ln),will be possible, thus improving reactor which migrate to the fuel periphery,economics by decreasing the amount Fuel-cladding chemicalcoming in contact with the cladding. Theof fuel required, and decreasing the interaction due to fissionresult of this interaction is degradationamount of nuclear waste generated.product lanthanidesof the cladding, and will eventuallyAccomplishments: can be prevented usinglead to rupture of the fuel assembly. TinThe technical goals of this research are additives to react withand palladium are being investigated asto explore the effectiveness of adding the lanthanides, thusminor component additives to controlminor additives to a metallic fuel extending the lifetimeFCCI in metallic fuels specifically dueto bind fission product lanthanides, and increasing theto lanthanides. The role of the additivewith the end goal of preventing or potential burn-up of ais to prevent FCCI by forming verydecreasing FCCI. To this end, both tin metallic fuel. stable intermetallic compounds with theand palladium were investigated during lanthanides, thus preventing interactionfiscal year (FY) 19. with the cladding. Previous studies investigated additives in a U-10Zr fuel.This report covers the evaluation of These studies have been extended tousing fuel additives (Pd and Sn) in U include U fuel, without Zr present. fuel, without Zr. To date, the as-cast Project Description:and annealed microstructures of USn, The technical objectives of this researchUSnLn, UPd, and UPdLn have been are to investigate additives to metallicevaluated (where Ln = 53Nd-25Ce-fuels for improved FCCI performance.16Pr-6La, and added to simulate fission Previous investigations using tin andproduct lanthanides). Diffusion couples palladium as fuel additives have shownbetween Fe and USn, UPd, and UPdLn promising results for controlling FCCI.are complete, and the SEM analysis is 170 2019|AFC ACCOMPLISHMENTS'