Fluorapatite, fluorinated calcium phosphate, has been identified as a potential matrix for the entombment of the zirconium fluoride fission product waste stream from the proposed FLEX process. If the efficacy of fluorapatite-based waste-storage can be demonstrated, then new and potentially more-efficient options for handling and separating high-level wastes, based on fluoride-salt extraction, will become feasible. This proposal will develop a dual-path research project to develop a process to fabricate a synthetic fluorapatite waste form for the ZrF4, FP waste stream, characterize the waste form, examine its performance under environmental conditions, and correlate the behavior of the waste form with natural analogs. Characterization of the material will be accomplished through probing the molecular-scale electronic and geometric structure of the materials in order to relate them to macroscopic properties, with the goal of developing techniques to evaluate and predict the performance of different waste-form materials. Time and funding permitting, other waste forms for the zirconium fluoride, fission product salt waste stream will be examined and benchmarked against the fluorapatite matrix baseline.
Highlights of Accomplishments:
1. Fluorapatite containing Sr and Zn surrogates (replacing the Ca) have been synthesized, annealed and analyzed using various techniques such as SEM, IR, XPS, Raman, DSC, TGA, EDS, XRD and XANES.
2. Non-annealed samples of the same surrogate samples have been analyzed with the same techniques.
3. The phosphate in fluorapatite and hydroxyapatite is not replaced by the nitrate ions of the surrogates during synthesis
