Papers by Author: Ashley Ewh

Abstract: U-Mo has thus far proven to be one of the most feasible metallic fuel alloys for use in research and test reactors due to its high density and stability during irradiation. However, an adverse diffusional interaction can occur between the fuel alloy and the Al based matrix. This forms an interaction layer (IL) that has undesirable thermal properties and irradiation behavior leading to accelerated swelling and reduced fuel efficiency. This study focused on the effects of ternary alloying additions on the formation of IL between U based alloys and Al. Diffusion couples of U-8Mo-3Nb, U-7Mo-6Zr, and U-10Nb-4Zr (wt.%) vs. pure Al were assembled and annealed at 600°C for 10 hours. Both thickness and phase constituent analyses were performed via electron microscopy. The major phase constituent of the IL was determined to be the UAl3 intermetallic compound. The Nb and Zr alloying additions did not reduce growth rate of IL (1.3~1.4 m/sec1/2) as compared to couples made between binary U-Mo and Al (0.9~1.8 m/sec1/2).

Abstract: This study examined the growth kinetics of intermetallic phases that develop in solid-tosolid diffusion couples assembled with U-7, 10 and 12wt.%Mo vs. Al alloys (Al, Al-2wt.%Si, Al- 5wt.%Si, 4043 and 6061) after a diffusion anneal at 550°C for 24 hours. Based on interdiffusion microstructure and integrated interdiffusion coefficients, the addition of Si into the Al matrix alloy was observed to significantly reduce the growth rate of the intermetallic layer that primarily consisted of (U,Mo)Al4 phase. Growth rate of the (U,Mo)Al4 intermetallic layer also increases slightly with Mo content; however, it was not significant compared to the effect of alloying Si into Al alloys. Growth kinetics of (U,Mo)Al4 intermetallic layer appear highly sensitive to composition of U-Mo fuel alloy and Al cladding alloys, and must be an important criteria in alloy development/selection for optimum fuel performance with due consideration for compositiondependent multicomponent interdiffusion.