Chemistry of Water Collected from an Unventilated Drift, Yucca Mountain, Nevada
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0985-NN13-03
Chemistry of Water Collected from an Unventilated Drift, Yucca Mountain, Nevada Brian D. Marshall1, Thomas A. Oliver2, and Zell E. Peterman1 1 WRD/YMPB, U.S. Geological Survey, WRD MS 963, Denver Federal Center, Denver, CO, 80225-0046 2 WRD/YMPB, S.M. Stoller Corp., c/o U.S. Geological Survey, WRD MS 963, Denver Federal Center, Denver, CO, 80225-0046
ABSTRACT Water samples (referred to as puddle water samples) were collected from the surfaces of a conveyor belt and plastic sheeting in the unventilated portion of the Enhanced Characterization of the Repository Block (ECRB) Cross Drift in 2003 and 2005 at Yucca Mountain, Nevada. The chemistry of these puddle water samples is very different than that of pore water samples from borehole cores in the same region of the Cross Drift or than seepage water samples collected from the Exploratory Studies Facility tunnel in 2005. The origin of the puddle water is condensation on surfaces of introduced materials and its chemistry is dominated by components of the introduced materials. Large CO2 concentrations may be indicative of localized chemical conditions induced by biologic activity. INTRODUCTION A key issue for the isolation of high-level radioactive waste in a proposed mined geologic repository constructed in the unsaturated zone at Yucca Mountain, Nevada, is the chemical composition of water that may be present in the emplacement drifts. Long-term estimates of the in-drift chemical environment rely on characterization of the ambient water chemistry [1] and on models that predict the perturbations to the ambient system. These perturbations are due primarily to thermal loading and secondarily to the interaction of the engineered barriers (e.g., waste packages) and introduced materials (e.g., rock bolts) with the ambient water chemistry [2]. The chemical compositions of samples of seepage into shallow underground workings at Yucca Mountain during the spring of 2005 are similar to pore water sampled from borehole cores, with minor influence from introduced construction materials in the immediate vicinity [3]. This paper summarizes the chemistry of water samples (referred to as puddle water samples) collected on surfaces of introduced materials in an unventilated drift. Table I. Dates of Isolation and Sampling in the ECRB Cross Drift at Yucca Mountain Bulkheads Closed Bulkheads Openeda Days Closed Gas Sampling Water Sampling 12/20/01 1/15/03, 2/3/03 391 3/12/02 to 8/2/02 1/15/03, 2/3/03 2/5/03 7/7/03 152 NAb 7/7/03 7/8/03 9/16/03 70 NA NA 10/29/03 1/25/05 454 NA 1/25/05 2/10/05 3/21/05 39 NA 3/21/05 3/21/05 6/3/05 74 NA 6/3/05, 6/14/05 6/16/05 12/1/05 168 NA 12/1/05c a b Not including times when only the first bulkhead at 17+63 m was opened. Not applicable. c These samples are not discussed in this report.
Figure 1. Shaded topographic map of Yucca Mountain, Nevada (base from USGS Busted Butte 7.5’ quadrangle). Underground workings shown with ticks at 100-m stations, bulkhead positions in the Enhanced Characterization of the Repository Block Cross Drift shown
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