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Water Migration and Swelling in Engineered Barrier Materials for Radioactive Waste Disposal

Published

Author(s)

Joanna McFarlane, Lawrence M Anovitz, Michael C. Cheshire, Victoria H. DiStefano, Hassina Z. Bilheux, Jean-Christophe Bilheux, Luke L. Daemen, Richard E. Hale, Ronald L. Howard, A. J. Ramirez-Cuesta, Louis J. Santodonato, Markus Bleuel, Daniel S. Hussey, David L. Jacobson, Jacob LaManna, Edmund Perfect, Logan Qualls

Abstract

Deep underground repositories are needed to isolate radioactive waste from the biosphere. Bentonite is an integral component of many multibarrier repository systems. Information on the hydraulic behavior of bentonite is needed for modeling the long-term viability of such systems. Bentonite samples were analyzed according to aggregate size, and different samples were subjected to hydrothermal treatments involving contact with NaCl, KCl, and deionized water. Neutron and xX-ray imaging were used to quantify water sorption into these packed bentonite samples and swelling of bentonite into the water column. Radiographs were imported into ImageJ and normalized with respect to the radiograph for the dry state. Because the wetting process was modeled in one dimension, intensity profiles were computed by averaging pixel rows. The distance between the original clay–water interface and the wetting front was determined as a function of time. Average water uptake exhibited a square root of time dependence in freshly prepared samples, with more variable rates for samples previously in contact with water. The radiography was supported by SANS and USANS for aggregate size distributions and by inelastic neutron scattering to understand the physicochemical environment of the water sorbed into the samples. Results showed that hydrothermal treatment with KCl had the greatest effect on water transport in the bentonite, possibly as a result of the interaction of K+ with illite layers in the clay mineral.
Citation
Nuclear Technology

Keywords

water uptake into bentonite, engineered clay barriers for nuclear fuel disposal, bentonite swelling, interfacial energy of water in porous bentonite, neutron radiography

Citation

McFarlane, J. , , L. , , M. , , V. , , H. , Bilheux, J. , , L. , Hale, R. , Howard, R. , , A. , Santodonato, L. , Bleuel, M. , , D. , , D. , LaManna, J. , Perfect, E. and Qualls, L. (2021), Water Migration and Swelling in Engineered Barrier Materials for Radioactive Waste Disposal, Nuclear Technology, [online], https://doi.org/10.1080/00295450.2020.1812348, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=930871 (Accessed September 22, 2021)
Created January 25, 2021, Updated April 30, 2021