title: Long-term non-isothermal reactive transport model of compacted bentonite, concrete and corrosion products in a HLW repository in clay.
abstract: Radioactive waste disposal in deep geological repositories envisages engineered barriers such as carbon-steel canisters, compacted bentonite and concrete liners. The stability and performance of the bentonite barrier could be affected by the corrosion products at the canister-bentonite interface and the hyper-alkaline conditions caused by the degradation of concrete at the bentonite-concrete interface. Additionally, the host clay formation could also be affected by the hyper-alkaline plume at the concrete-clay interface. Here we present a non-isothermal multicomponent reactive transport model of the long-term (1Ma) interactions of the compacted bentonite with the corrosion products of a carbon-steel canister and the concrete liner of the engineered barrier of a high-level radioactive waste repository in clay. Model results show that magnetite is the main corrosion product. Its precipitation reduces significantly the porosity of the bentonite near the canister. The degradation of the concrete liner leads to the precipitation of secondary minerals and the reduction of the porosity of the bentonite and the clay formation at their interfaces with the concrete liner. The reduction of the porosity becomes especially relevant at t=104years. The zones affected by pore clogging at the canister-bentonite and concrete-clay interfaces at 1Ma are approximately equal to 1 and 3.3cm thick, respectively. The hyper-alkaline front (pH>8.5) spreads 2.5cm into the clay formation after 1Ma. Our simulation results share the key features of the models reported by others for engineered barrier systems at similar chemical conditions, including: 1) Pore clogging at the canister-bentonite and concrete-clay interfaces; 2) Narrow alteration zones; and 3) Limited smectite dissolution after 1Ma.
authors.affiliation: Centro de Investigaciones Científicas Avanzadas (CICA), E.T.S. Ingenieros de Caminos, Canales y Puertos, Campus de Elviña, University of A Coruña, 15071 La Coruña, Spain.
authors.forename: Alba
authors.initials: A
authors.lastname: Mon
authors.affiliation: Centro de Investigaciones Científicas Avanzadas (CICA), E.T.S. Ingenieros de Caminos, Canales y Puertos, Campus de Elviña, University of A Coruña, 15071 La Coruña, Spain. Electronic address: j.samper@udc.es.
authors.forename: Javier
authors.initials: J
authors.lastname: Samper
authors.affiliation: Centro de Investigaciones Científicas Avanzadas (CICA), E.T.S. Ingenieros de Caminos, Canales y Puertos, Campus de Elviña, University of A Coruña, 15071 La Coruña, Spain.
authors.forename: Luis
authors.initials: L
authors.lastname: Montenegro
authors.affiliation: Centro de Investigaciones Científicas Avanzadas (CICA), E.T.S. Ingenieros de Caminos, Canales y Puertos, Campus de Elviña, University of A Coruña, 15071 La Coruña, Spain.
authors.forename: Acacia
authors.initials: A
authors.lastname: Naves
authors.affiliation: Centro de Investigaciones Científicas Avanzadas (CICA), E.T.S. Ingenieros de Caminos, Canales y Puertos, Campus de Elviña, University of A Coruña, 15071 La Coruña, Spain.
authors.forename: Jesús
authors.initials: J
authors.lastname: Fernández
mesh_terms: D000538:Aluminum Silicates; D001546:Bentonite; D000077215:Clay; D003343:Corrosion; D006863:Hydrogen-Ion Concentration; D008962:Models, Theoretical; D016062:Porosity; D011850:Radioactive Waste; D012037:Refuse Disposal / Q000379:methods; D064091:Waste Disposal Facilities
chemical_list: D000538:Aluminum Silicates; D011850:Radioactive Waste; D001546:Bentonite; D000077215:Clay
keywords: CORE(2D); Compacted bentonite barrier; Concrete; Corrosion products; Hyper-alkaline pH front; Radioactive waste disposal; Reactive transport