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Conditions and processes affecting radionuclide transport

Ardyth M. Simmons and Leonid A. Neymark
Conditions and processes affecting radionuclide transport (in Hydrology and geochemistry of Yucca Mountain and vicinity, southern Nevada and California, John S. Stuckless (editor))
Memoir - Geological Society of America (October 2012) 209: 277-362

Abstract

Characteristics of host rocks, secondary minerals, and fluids would affect the transport of radionuclides from a previously proposed repository at Yucca Mountain, Nevada. Minerals in the Yucca Mountain tuffs that are important for retarding radionuclides include clinoptilolite and mordenite (zeolites), clay minerals, and iron and manganese oxides and hydroxides. Water compositions along flow paths beneath Yucca Mountain are controlled by dissolution reactions, silica and calcite precipitation, and ion-exchange reactions. Radionuclide concentrations along flow paths from a repository could be limited by (1) low waste-form dissolution rates, (2) low radionuclide solubility, and (3) radionuclide sorption onto geological media. The chief sources of radioactivity in spent nuclear fuel are americium, plutonium, and neptunium. Therefore, studies have concentrated on their geochemical mobility. Uranium-233, uranium-234, iodine-129, technetium-99, and other radionuclides also have been included in some experiments. Solubilities were determined experimentally in representative Yucca Mountain waters. Sorption coefficients were determined using water, rock, and pure mineral samples from Yucca Mountain. Batch experiments were performed at several pH levels and oxidizing conditions. Dynamic transport-column experiments, diffusion experiments, and solid-rock beaker experiments also were conducted. The batch tests gave slightly lower retardation factors than those derived from column-breakthrough experiments. This finding indicates that using batch-sorption coefficients to predict radionuclide transport will yield conservative results in a performance assessment. Understanding of unsaturated-zone transport is based on laboratory and field-scale experiments. Fractures provide advective transport pathways. Sorption and matrix diffusion may contribute to retardation of radionuclides. Conversely, sorption onto mobile colloids may enhance radionuclide transport.


ISSN: 0072-1069
Coden: GSAMAQ
Serial Title: Memoir - Geological Society of America
Serial Volume: 209
Title: Conditions and processes affecting radionuclide transport
Title: Hydrology and geochemistry of Yucca Mountain and vicinity, southern Nevada and California
Author(s): Simmons, Ardyth M.Neymark, Leonid A.
Author(s): Stuckless, John S.editor
Affiliation: Los Alamos National Laboratory, Los Alamos, NM, United States
Affiliation: U. S. Geological Survey, Denver, CO, United States
Pages: 277-362
Published: 201210
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
ISBN: 978-0-8137-1209-3
References: 277
Accession Number: 2012-101404
Categories: HydrogeologyIsotope geochemistry
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. block diags., 22 tables, sketch maps
N36°43'60" - N37°00'00", W116°34'60" - W116°25'00"
Secondary Affiliation: U. S. Geological Survey, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201252
Program Name: USGSOPNon-USGS publications with USGS authors
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