title: Corrosion of high-level radioactive waste iron-canisters in contact with bentonite.
abstract: Several countries favor the encapsulation of high-level radioactive waste (HLRW) in iron or steel canisters surrounded by highly compacted bentonite. In the present study the corrosion of iron in contact with different bentonites was investigated. The corrosion product was a 1:1 Fe layer silicate already described in literature (sometimes referred to as berthierine). Seven exposition test series (60 °C, 5 months) showed slightly less corrosion for the Na-bentonites compared to the Ca-bentonites. Two independent exposition tests with iron pellets and 38 different bentonites clearly proved the role of the layer charge density of the swelling clay minerals (smectites). Bentonites with high charged smectites are less corrosive than bentonites dominated by low charged ones. The type of counterion is additionally important because it determines the density of the gel and hence the solid/liquid ratio at the contact to the canister. The present study proves that the integrity of the multibarrier-system is seriously affected by the choice of the bentonite buffer encasing the metal canisters in most of the concepts. In some tests the formation of a patina was observed consisting of Fe-silicate. Up to now it is not clear why and how the patina formed. It, however, may be relevant as a corrosion inhibitor.
authors.affiliation: BGR, Bundesanstalt für Geowissenschaften und Rohstoffe, Stilleweg 2, D-30655 Hannover, Germany. Electronic address: s.kaufhold@bgr.de.
authors.forename: Stephan
authors.initials: S
authors.lastname: Kaufhold
authors.affiliation: Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Straße 1, D-40237 Düsseldorf, Germany; Institute for Chemical Technology of Inorganic Materials, Johannes Kepler University Linz, Altenberger Straße 69, 4040 Linz, Austria.
authors.forename: Achim Walter
authors.initials: AW
authors.lastname: Hassel
authors.affiliation: Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Straße 1, D-40237 Düsseldorf, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Sanders
authors.affiliation: BGR, Bundesanstalt für Geowissenschaften und Rohstoffe, Stilleweg 2, D-30655 Hannover, Germany; LBEG, Landesamt für Bergbau, Energie und Geologie, Stilleweg 2, D-30655 Hannover, Germany.
authors.forename: Reiner
authors.initials: R
authors.lastname: Dohrmann
mesh_terms: D001546:Bentonite / Q000737:chemistry*; D011232:Chemical Precipitation; D003343:Corrosion; D007501:Iron / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D011850:Radioactive Waste; D012995:Solubility; D018505:Waste Management; D014961:X-Ray Diffraction
chemical_list: D011850:Radioactive Waste; D001546:Bentonite; D007501:Iron
keywords: Bentonite; Bentonite–iron-interaction; Corrosion; High-level radioactive waste canister; Iron