U.S. Department of Energy

Pacific Northwest National Laboratory

Outcomes: Fundamental Understanding of Nucleation Processes to Assess Solution Stability and Phase Growth and Genesis

Principal Investigator: Gregg Lumetta

Completed: FY18

Outcomes: The focus was on creating a physicochemical framework for examining and predicting precipitation reactions relevant to nuclear materials processing and nuclear forensics. Experimental and computational methods probed plutonium oxalate nucleation and growth (europium oxalate was used in most experiments). Various microscopy tools were employed, investigating growth rates down to nanometer resolution. Growth rates were fit to theoretical models to deduce growth pathways. The project explored a novel approach for developing electronic parameters to describe crystallinity and surface tension of nanocrystals (using sodium chloride as a case study).  

Other project outcomes included creation of a Cryo-Transmission Electron Microscopy capability in PNNL's Radiochemical Processing Laboratory, and successful modeling of europium oxalate growth with a diffusion limited growth mechanism, which found that localized inhomogeneities due to mixing played an important role in the crystal growth. The project also applied machine learning to predict surface tensions controlling kinetics of nucleation and crystallization processes.

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