In situ testing of the chemical durability of vitrified high-level waste in a Boom Clay formation in Belgium: discussion of recent data and concept of a new test

SCK-CEN has been conducting in situ experimental programmes on candidate hi gh-level waste (HLW) glasses, as part of a global approach to evaluate the long-term chemical durability of the HLW glasses. The in situ tests are con ducted in the underground research facility high activity disposal experime ntal site (HADES). located in the Boom Clay at 223 m below the SCK-CEN site . We briefly present the test concepts for three in situ tests: a first typ e of corrosion test. tests as part of the Control Experiment with Radiation of the Belgian Repository for Underground Storage (CERBERUS) test (involvi ng gamma -radiation sources), and the CORrosion of Active gLass in Undergro und Storage condition (CORALUS) test, that involves both gamma -sources and glass samples doped with a-radionuclides (Np, Pu. Am). The glasses are cor roded slightly less compared with the first in situ tests (where no gamma - radiation was present). By using mass loss data and an extensive analysis o f the reaction layer formed on top of the glasses, we managed to identify t he main interaction processes: matrix dissolution and selective leaching. T he four glasses studied reveal significant differences in dissolution behav iour. We further discuss the status of the CORALUS in situ corrosion test, which is in its first phase, An inactive CORALUS tube has been prepared and is presently in operation. (C) 2001 Elsevier Science B.V. All rights reser ved.