The application of in situ formed mixed iron oxides in the removal of strontium and actinides from nuclear tank waste

Abstract

This article discusses the experimental program conducted at Argonne National Laboratory to study the performance of in situ formed mixed iron oxides (IS-MIO) for the removal of strontium (Sr), plutonium (Pu), neptunium (Np), uranium (U), and americium (Am) from the Savannah River Site (SRS) radioactive tank waste. The boundaries for the experimental work were defined in collaboration with SRS. IS-MIO was actually found to be a mixture of Fe(II) and Fe(III) oxides and hydroxides, including magnetite. Decontamination factor (DF) values were measured for both IS-MIO and monosodium titanate (MST), the baseline sorbent used by SRS. DF values for IS-MIO were found to be superior to MST for all isotopes studied. DF values for Pu, Np, and Sr, achieved within 30 min of IS-MIO formation were orders of magnitude larger than the needed values. DF values for U and Am were less than the former three but still acceptable, and greater than MST. V V C 2010 American Institute of Chemical Engineers AIChE J, 56: 3012-3020, 2010

SRNL LDRD Program Report 2012

“…The first discharge capacity of the AlH 3 , LiAlH 4 and NaAlH 4 is around 2760 mAh/g (theoretical 2679 mAh/g), 2260 mAh/g (theoretical 2118mAh/g) and 2090 mAh/g (theoretical 1488 mAh/g), respectively. The higher values (than theoretical) are attributed to the irreversible formation of the solid electrolyte interface (SEI).…”

“…Raman spectroscopy ( Figure 1) suggests that the materials transition to another uranyl species as rapidly as 1 week (95% relative humidity) while lower humidity studies where still reactive after several weeks. Although the Raman bands can only tentatively be defined as associated with uranyl hydroxide, powder XRD measurements suggest the initial material is consistent with metastudtite (a di-hydrate uranyl phase with the formula UO 4 •2H 2 O) whilst the most aged samples particles are consistent with studtite (a tetra-hydrate uranyl phase with the formula UO 4 •4H 2 O). Additional analyses (fluorescence, TEM, Auger electron, and others) are planned to confirm these results.…”

“…Thermal gravimetric and differential thermal analysis techniques were used to determine to what extent these solid fluorinators might fluorinate both clean surrogate materials representative of both volatile and nonvolatile fluoride species, as well as uranium oxide materials. Thus far it appears that the clean surrogate materials are fluorinating as expected to form such products as SrF 2 and MoF 6 , however experiments conducted with both XeF 2 and NH 4 HF 2 have not yielded evidence of fluorination of UO 2 or U 3 O 8 to form either UF 4 or UF 6 . This area of study is being continued in the laboratory of Prof. Knight by graduate student Dillon Inabinett who will be studying alternate fluorination species as part of his Master's degree thesis.…”

“…These insoluble oxides passivate the catalyst surface, eventually hindering the ORR 3 . In addition, precipitates block gas channels leading to oxygen mass transport resistance which limits the cells to low operating current densities 4 . The introduction of atmospheric air adds parasitic reaction species, such as humidity, which can SRNL-STI-2013-00161 diffuse and oxidize the lithium anode.…”

“…The figure on the left shows a comparison of the first full charge/discharge cycle (FDC) of AlH 3 , LiAlH 4 and NaAlH 4 . The first discharge capacity of the AlH 3 , LiAlH 4 and NaAlH 4 is around 2760 mAh/g (theoretical 2679 mAh/g), 2260 mAh/g (theoretical 2118mAh/g) and 2090 mAh/g (theoretical 1488 mAh/g), respectively.…”