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Title: Uranium-Series Constraints on Radionuclide Transport and Groundwater Flow Beneath the Nopal I Uranium Deposit, Sierra Pena Blanca, Mexico

Abstract

No abstract prepared.

Authors:
; ; ;
Publication Date:
Research Org.:
Yucca Mountain Project, Las Vegas, Nevada
Sponsoring Org.:
USDOE
OSTI Identifier:
894171
Report Number(s):
NA
MOL.20060905.0129, DC# 47783; TRN: US0700115
DOE Contract Number:
NA
Resource Type:
Conference
Resource Relation:
Conference: 2006 Internantional High-Level Radioactive Waste Management Conference, May 02, 2006 Las Vegas, NV
Country of Publication:
United States
Language:
English
Subject:
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS; 12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; HIGH-LEVEL RADIOACTIVE WASTES; MANAGEMENT; MEXICO; RADIOISOTOPES; TRANSPORT; URANIUM DEPOSITS

Citation Formats

S. Foldstein, S. Luo, R. Ku, and M. Murrell. Uranium-Series Constraints on Radionuclide Transport and Groundwater Flow Beneath the Nopal I Uranium Deposit, Sierra Pena Blanca, Mexico. United States: N. p., 2006. Web.
S. Foldstein, S. Luo, R. Ku, & M. Murrell. Uranium-Series Constraints on Radionuclide Transport and Groundwater Flow Beneath the Nopal I Uranium Deposit, Sierra Pena Blanca, Mexico. United States.
S. Foldstein, S. Luo, R. Ku, and M. Murrell. Thu . "Uranium-Series Constraints on Radionuclide Transport and Groundwater Flow Beneath the Nopal I Uranium Deposit, Sierra Pena Blanca, Mexico". United States. doi:. https://www.osti.gov/servlets/purl/894171.
@article{osti_894171,
title = {Uranium-Series Constraints on Radionuclide Transport and Groundwater Flow Beneath the Nopal I Uranium Deposit, Sierra Pena Blanca, Mexico},
author = {S. Foldstein and S. Luo and R. Ku and M. Murrell},
abstractNote = {No abstract prepared.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Thu Apr 27 00:00:00 EDT 2006},
month = {Thu Apr 27 00:00:00 EDT 2006}
}

Conference:
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  • Uranium-series data for groundwater samples from the vicinity of the Nopal I uranium ore deposit are used to place constraints on radionuclide transport and hydrologic processes at this site, and also, by analogy, at Yucca Mountain. Decreasing uranium concentrations for wells drilled in 2003 suggest that groundwater flow rates are low (< 10 m/yr). Field tests, well productivity, and uranium isotopic constraints also suggest that groundwater flow and mixing is limited at this site. The uranium isotopic systematics for water collected in the mine adit are consistent with longer rock-water interaction times and higher uranium dissolution rates at the frontmore » of the adit where the deposit is located. Short-lived nuclide data for groundwater wells are used to calculate retardation factors that are on the order of 1,000 for radium and 10,000 to 10,000,000 for lead and polonium. Radium has enhanced mobility in adit water and fractures near the deposit.« less
  • Uranium-series data for groundwater samples from the Nopal I uranium ore deposit were obtained to place constraints on radionuclide transport and hydrologic processes for a nuclear waste repository located in fractured, unsaturated volcanic tuff. Decreasing uranium concentrations for wells drilled in 2003 are consistent with a simple physical mixing model that indicates that groundwater velocities are low ({approx}10 m/y). Uranium isotopic constraints, well productivities, and radon systematics also suggest limited groundwater mixing and slow flow in the saturated zone. Uranium isotopic systematics for seepage water collected in the mine adit show a spatial dependence which is consistent with longer water-rockmore » interaction times and higher uranium dissolution inputs at the front adit where the deposit is located. Uranium-series disequilibria measurements for mostly unsaturated zone samples indicate that {sup 230}Th/{sup 238}U activity ratios range from 0.005-0.48 and {sup 226}Ra/{sup 238}U activity ratios range from 0.006-113. {sup 239}Pu/{sup 238}U mass ratios for the saturated zone are <2 x 10{sup -14}, and Pu mobility in the saturated zone is >1000 times lower than the U mobility. Saturated zone mobility decreases in the order {sup 238}U{approx}{sup 226}Ra > {sup 230}Th{approx}{sup 239}Pu. Radium and thorium appear to have higher mobility in the unsaturated zone based on U-series data from fractures and seepage water near the deposit.« less
  • The Nopal I uranium deposit in Chihuahua, Mexico, is an excellent analogue for evaluating the fate of spent fuel, associated actinides, and fission products over long time scales for the proposed Yucca Mountain high-level nuclear waste repository. In 2003, three groundwater wells were drilled directly adjacent to (PB-1) and 50 m on either side of the uranium deposit (PB-2 and PB-3) in order to evaluate uranium-series transport in three dimensions. After drilling, uranium concentrations were elevated in all of the three wells (0.1-18 ppm) due to drilling activities and subsequently decreased to {approx}5-20% of initial values over the next severalmore » months. The {sup 234}U/{sup 238}U activity ratios were similar for PB-1 and PB-2 (1.005 to 1.079) but distinct for PB-3 (1.36 to 1.83) over this time period, suggesting limited mixing between groundwater from these wells over these short time and length scales. Regional groundwater wells located up to several km from the deposit also have distinct uranium isotopic characteristics and constrain mixing over larger length and time scales. We model the decreasing uranium concentrations in the newly drilled wells with a simple one-dimensional advection-dispersion model, assuming uranium is introduced as a slug to each of the wells and transported as a conservative tracer. Using this model for our data, the relative uranium concentrations are dependent on both the longitudinal dispersion as well as the mean groundwater flow velocity. These parameters have been found to be correlated in both laboratory and field studies of groundwater velocity and dispersion (Klotz et al., 1980). Using typical relationships between velocity and dispersion for field and laboratory studies along with the relationship observed from our uranium data, both velocity (1-10 n/yr) and dispersion coefficient (1E-5 to 1E-2 cm{sup 2}/s) can be derived from the modeling. As discussed above, these relatively small flow velocities and dispersivities agree with mixing considerations derived from the {sup 234}U/{sup 238}U data. While these results and the limited productivity of these wells consistently suggest limited groundwater flow and mixing, we anticipate additional work with artificial tracers to better establish groundwater flow velocities and gradient at this site.« less