Tunnel Boring Machine (TBM)
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Geochemical compositions were determined for dust samples collected throughout the 7-kilometer-long Exploratory Studies Facility (ESF) tunnel at Yucca Mountain, Nevada. In a geologic repository for nuclear waste, the chemical composition of dust that may settle on waste canisters is of concern in that certain elements or compounds may accelerate canister corrosion.

Major, minor, and trace-element analysis of samples indicated that dust generated by crushing of tuffs in the ESF at Yucca Mountain during tunnel construction was mixed with a variety of anthropogenic components. Relative to the mean composition of the host rock (Topopah Spring Tuff rhyolite), the dust is enriched in FeO, MgO, CaO, TiO₂, MnO, CI, F, and CO₂.

All of the organic carbon in the dust has been introduced by anthropogenic activities because the rocks are devoid of organic carbon. The enrichment of metals in the dust compared to host rock compositions indicates introduction during construction. Other relations indicate that salts of evaporated construction water, which was flagged with lithium bromide and native pore water are important components of the dust. If the dust accumulates on waste canisters and gets wet, these soluble constituents will be dissolved or may form deliquescence compounds under conditions of high humidity and accelerate the rates of canister corrosion by forming corrosive brines.

Text from Peterman, Zell E., Paces, J.B., Neymark, L.A>, and Hudson, D., 2002, "Geochemistry of Dust in the Exploratory Studies Facility, Yucca Mountain, Nevada, Las Vegas, Nevada, March 30-April 2, in the proceedings of the Tenth International Conference of High-Level Radioactive Waste Management,:La Grange Park, IL, American Nuclear Society, p. 637-645.

U.S. Department of the Interior U.S. Geological Survey
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