PNNL

Abstract

This report provides experimental details and results of evaluating aluminophosphate waste forms for treating and immobilizing the salt cations from salt wastes generated during electrochemical reprocessing of used nuclear fuel. In the waste form process for these materials, chloride salt streams are reacted with NH4H2PO4, the chlorine is removed from the salts and driven off as NH4Cl (a solid condensate that can be captured), and then the product can be vitrified in conjunction with glass-forming chemicals (e.g., Fe2O3, Al2O3) to create a high-durability waste form. This study was initiated with some literature review on aluminophosphates containing high alkali oxide content and some of this information is summarized in this report. Following literature review, three new samples were synthesized where two contained Fe2O3+Al2O3 (i.e., samples G3 and G5) and one was only Al2O3 (Fe2O3-free) (i.e., sample G6). In addition to these samples, G1 was also made, which is the baseline reference waste form referred to as DPF5-336 (made without Al2O3). Samples G1, G3, G5, and G6 had phases of Li3Fe2(PO4)3 (likely), monazite (below XRD detection limits), AlPO4, and AlPO4, respectively. Characterizations on these materials included optical images, scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction. These samples were shipped to Argonne National Laboratory for chemical durability testing. Depending on how the samples perform in these tests, an additional phase of aluminophosphate formulations could be designed and tested. This report completes the milestone M4FT-23PN030104041 with details provided in Appendix B.