The Hanford site near Richland Washington,
United States, is staging
some of its 56 million gallons of high-level waste for treatment.
Limited understanding of solids precipitated from the concentrated
electrolyte solutions complicates the development of waste treatment
options. The implications for the precipitation of these solids are
that overlying liquids are saturated in these salts, which may cause
unwanted precipitation during downstream processing. This study characterizes
the salts in two of these Hanford staged feed tanks (Tanks AP-103
and AP-108) by ion chromatography (for anions), X-ray diffraction,
polarized light microscopy, and scanning electron microscopy with
energy dispersive X-ray spectroscopy. The results show that Na2CO3·H2O (thermonatrite) was the
most prevalent salt in one tank, whereas the double salt Na7F(PO4)2·19H2O (natrophosphate)
was the dominant salt in the other. Natrophosphate occurred in both
tanks as octahedrons in sizes ranging from 10 μm to a millimeter
in diameter. Natroxalate (Na2C2O4) and kogarkoite (NaFSO4) were also common phases observed.
Waste processing planners should recognize that these salts may have
to be dissolved prior to treatment, and solutions saturated with these
salts may complicate downstream processing.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.