The potential effect of cementitious colloids on radionuclide mobilisation in a repository for radioactive waste |
| |
| Affiliation: | 1. Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA;2. Pacific Northwest National Laboratory, Richland, WA 99352, USA;3. Los Gatos Research, Mountain View, CA 94041-1529, USA;4. Akonni Biosystems, Inc., 400 Sagner Avenue, Suite 300, Frederick, MD 21701, USA;5. Haley & Aldrich, Inc., 501 River St. #100, Greenville, SC 29601, USA;6. Department of Molecular Biology and Genetics, 321 Biotechnology Building, Cornell University, Ithaca, NY 14853, USA;7. Earth and Planetary Science and Environmental Science, Policy, and Management, University of California-Berkeley, Berkeley, CA 94720, USA;8. Department of Microbiology, University of Massachusetts, Amherst, MA 01003, USA;1. Karlsruhe Institute of Technology, Institute for Nuclear Waste Disposal, P.O. Box 3640, 76021 Karlsruhe, Germany;2. Amphos 21 Consulting S.L., Passeig de Garcia i Fària 49-51 1°-1a, E08019 Barcelona, Spain;3. Svensk Kärnbränslehantering AB, Avd. Låg–och medelaktivt Avfall, Evenemangsgatan 13 Box 3091, 169 03 Solna, Sweden;1. Research Centre for Radwaste Disposal and Williamson Research Centre, School of Earth, Atmospheric and Environmental Sciences, The University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom;2. National Nuclear Laboratory, Chadwick House, Risley WA3 6AE, United Kingdom;3. Centre for Radiochemistry Research, School of Chemistry, The University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom;4. Diamond Light Source Ltd., Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, United Kingdom;1. Amphos 21 Consulting SL, Passeig de Garcia i Fària 49-51, 08019, Barcelona, Spain;2. Belgian Agency for Radioactive Waste and Enriched Fissile materials (ONDRAF/NIRAS), Avenue des Arts 14, 1210, Brussels, Belgium;3. Fundació CTM Centre Tecnològic, Environmental Technology Area, Plaça de la Ciència, 2, 08243, Manresa, Spain |
| |
| Abstract: | Colloid-facilitated transport of contaminants could enhance the release rate of radionuclides from the cementitious near field of a repository for radioactive waste. In the current design of the planned Swiss repository for intermediate-level radioactive waste, a gas-permeable mortar is employed as backfill material for the engineered barrier. The main components of the material are hardened cement paste (HCP) and quartz aggregates. The chemical condition in the backfill mortar is controlled by the highly alkaline cement pore water present in the large pore space. The interaction of pore water with the quartz aggregates is expected to be the main source for colloids. Colloid transport is facilitated due to the high porosity of the backfill mortar. Batch-type studies have been performed to generate colloidal material in systems containing crushed backfill mortar or quartz in contact with artificial cement pore water (ACW) at pH 13.3. The chemical composition of the colloidal material corresponds to that of calcium silicate hydrates (CSH). Batch flocculation tests show that, after about 20 days reaction time, the concentration of the CSH-type colloids is typically below 0.1 mg l−1 due to reduced colloid stability in ACW. Uptake studies with Cs(I), Sr(II) and Th(IV) on a CSH phase (initial C:S ratio=1.09) have been carried out to assess the sorption properties of the colloidal material. The influence of uptake by colloids on radionuclide mobilisation is expressed in terms of sorption reduction on the immobile phase (HCP). Sorption reduction factors can be estimated on the assumption that the sorption properties of the colloidal material are either similar to those of the CSH phase or HCP, and that sorption is linear and reversible. A scaling factor accounts for the higher specific surface area of the colloidal material compared to the CSH phase and HCP. At colloid concentration levels typically encountered in highly alkaline cement pore waters, colloid-induced sorption reduction is predicted to be negligibly small even for strongly sorbing radionuclides, such as Th(IV). Thus, no significant impact of cementitious colloids on radionuclide mobilisation in the porous backfill mortar is anticipated. |
| |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
