Characterization of Neptunium Oxide Product from Modified Direct Denitration Process

The²³⁸Pu Supply Program at Oak Ridge National Laboratory (ORNL) produces²³⁷Np targets for production of²³⁸Pu. The program utilizes a modified direct denitration (MDD) chemical process for production of NpO2 for targets. To meet ongoing needs for space power applications, continual optimization of target production, including production of reliable NpO2/Al pellets, is paramount. Research and development regarding the MDD process seeks to provide continual input into process adjustment for the most consistent production flowsheet. An ongoing effort to characterize solids produced in the MDD process is addressing the potential for variability in Np powder products during multiple steps in the MDD process. MDD solid products were analyzed using powder x-ray diffraction (pXRD) and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) to identify differences in products between MDD batches as well as differences before and after high firing of the product. Broadly, the MDD product was found to be a mixture of NpO2 and Np2O5, with ratios varying between runs. The origin or cause of variability in MDD product between batches has not yet been determined. After high firing, all product was found to be pure NpO2. Morphology and particle size of the MDD product differs between MDD runs, but the final, high-fired product has consistent particle size and morphology.