Quantitative assessment of radionuclide retention in the Quaternary sediments/granite interface of the Fennoscandian shield (Sweden)

• Published in: Applied geochemistry Vol. 26; no. 5; pp. 679 - 687
• Main Authors: Grandia, Fidel, Sena, Clara, Arcos, David, Molinero, Jorge, Duro, Lara, Bruno, Jordi
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.05.2011; Elsevier
• Subjects: administered dose; adsorption; barite; calcite; cation exchange; coprecipitation; Earth sciences; Earth, ocean, space; ecosystems; Engineering and environment geology. Geothermics; Exact sciences and technology; ferrihydrite; Geochemistry; granite; groundwater; illite; mathematical models; Pollution, environment geology; radioactive waste; radionuclides; sediments; strontium; Sweden; Scandinavia; Europe; illite; till; oxides; ground water; calcite; sulfates; radionucleids; storage; Earth; precipitation; aquifers; granites; ferrihydrite; sheet silicates; silicates; Cenozoic; retention; barite; adsorption; cations; interfaces; Quaternary; host rocks; concentration; igneous rocks; transport; carbonates; intrusions; hydroxides; shields; numerical models; ecosystems; plutonic rocks; clay minerals; Phanerozoic
• ISSN: 0883-2927; 1872-9134
• DOI: 10.1016/j.apgeochem.2011.01.026

► The release of radionuclides from a deep geological repository is investigated. ► We simulate the transport of radionuclides in a Quaternary sediment. ► The Quaternary sediment’s geochemistry is studied to select the reactive minerals. ► U, Sr, Cs and Ra were selected due to their contribution for the radioactive dose. ► The retention capacity of the Quaternary sediments was quantitatively evaluated. The Quaternary sediments representing the interface between the granite host rock and the Earth surface are of paramount importance when determining the potential cycling of anthropogenic and natural radionuclides in near-surface systems. This is particularly true in the case of high-level nuclear waste (HLNW) repositories placed in granite. In this work a modelling procedure is presented to quantitatively determine the retention capacity of a Quaternary till in the Forsmark area, which has been recently selected to host the deep geologic storage of HLNW in Sweden. Reactive transport numerical models have been used to simulate the intrusion of a deep groundwater carrying radionuclides potentially released from a repository into a Quaternary till. Four radionuclides (235U, 135Cs, 226Ra and 90Sr) have been selected according to their different geochemical behaviour and potential dose relevance to surface ecosystems. Numerical results indicate that repository-derived: (i) U will have a minor impact in the till, mainly due to the high natural concentration of U and its adsorption on ferrihydrite; (ii) Cs will be efficiently retained by cation exchange on illite; (iii) Ra will be retained via co-precipitation with barite; and although (iv) Sr will be retained via co-precipitation with calcite and cation exchange on illite, the retention capacity of the Quaternary till for Sr is limited.