Iron and manganese in oxide minerals and in glasses: preliminary consideration of Eh buffering potential at Yucca Mountain, Nevada

Technical Report · Mon Apr 01 04:00:00 EST 1985

DOI:https://doi.org/10.2172/59186· OSTI ID:59186

Caporuscio, F A; Vaniman, D T

The tuffs of Yucca Mountain at the Nevada Test Site are currently under investigation as a possible deep burial site for high-level radioactive waste disposal. One of the main concerns is the effect of oxidizing groundwater on the transport of radionuclides. Rock components that may affect the oxygen content of groundwater include Fe-Ti oxides, Mn oxides, and glasses that contain ferrous iron. Some phenocryst Fe-Ti oxides at Yucca Mountain are in reduced states, whereas groundmass Fe-Ti oxides have been oxidized to hematite, rutile, and pseudobrookite (Fe{sup 3+}-bearing phases) exclusively. Estimates of Fe{sup 2+}-bearing oxides indicate that less than 0.33 vol% phenocrysts is available to act as solid buffering agents of Eh. Of this percentage, significant amounts of Fe-Ti oxides are isolated from effective interaction with groundwater because they occur in densely welded, devitrified tuffs that have low interstitial permeability. Manganese oxides occur primarily along fractures in the ash-flow tuffs. Because the Mn oxides are concentrated along the same pathways (fractures) where transport has occurred in the past, these small volume percentages could act as buffers. However, the oxidation states of actual Mn-oxide phases are high (Mn{sup 4+}), and these minerals have virtually no potential for reducing groundwater Eh. Manganese oxides may even act as oxidizing agents. However, regardless of their poor capabilities as reducing agents, the Mn oxides could be important as sorbents of heavy metals at Yucca Mountain. The lack of accessible, pristine Fe-Ti oxides and the generally high oxidation states of Mn oxides seem to rule out these oxides as Eh buffers of the Yucca Mountain groundwater system. Reduction of ferrous iron within glassy tuffs may have some effect on Eh, but further study is needed. At present it is prudent to assume that minerals and glasses have little or no capacity for reducing oxygen-rich groundwater at Yucca Mountain. 25 refs., 3 figs., 12 tabs

• Research Organization: Los Alamos National Lab., NM (United States)
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 59186
• Report Number(s): LA--10369-MS; ON: DE85011892
• Country of Publication: United States
• Language: English

Related Subjects

05 NUCLEAR FUELS
58 GEOSCIENCES
BOREHOLES
BUFFERS
GEOLOGIC FRACTURES
GLASS
GROUND WATER
HEMATITE
HIGH-LEVEL RADIOACTIVE WASTES
IRON OXIDES
MANGANESE OXIDES
OXIDE MINERALS
OXYGEN
RADIOACTIVE WASTE DISPOSAL
RADIONUCLIDE MIGRATION
REDOX POTENTIAL
REMOVAL
ROCK-FLUID INTERACTIONS
RUTILE
SORPTIVE PROPERTIES
TITANIUM OXIDES
TUFF
VALENCE
YUCCA MOUNTAIN
Yucca Mountain Project