U.S. Department of Energy

Pacific Northwest National Laboratory

Outcomes: Ion Implantation and Characterization of Epsilon Metal Phase Formation in Ceria

Principal Investigator: Ram Devanathan

Completed: FY19

Outcomes: This project filled key knowledge gaps in noble metal particle formation in irradiated nuclear fuel, which could enhance the safety and economics of nuclear energy. It tackled the challenge of identifying alloy nanoparticle formation mechanisms. The project took a novel approach, combining computer simulations of radiation damage, thermodynamic calculations, and ion bombardment of a surrogate material to enhance understanding of nuclear fuel. Researchers irradiated ceria doped with molybdenum (Mo), ruthenium (Ru), rhodium (Rh), palladium (Pd) and rhenium (Re). The samples were characterized with electron microscopy and elemental mapping from selected areas. Researchers also analyzed the thermodynamic properties of high entropy alloy particles. Significantly, the project found that radiation-enhanced diffusion plays an important role in initial stages of nanoparticle formation and thermal diffusion contributes to alloying and particle coarsening. The researchers further found that MoRuRhPd-based alloys are thermodynamically stable as single-phase solid solutions over a broad composition range. The project established external collaborations for in situ characterization of nanoparticle formation and connected the findings with results of a similar NPSI project on uranium dioxide.

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