The study of abiotic reduction of nitrate and nitrite in Boom Clay

In Belgium, Boom Clay is studied as a reference host rock for the geological disposal of high-level and intermediate-level radioactive waste. Compatibility studies at the SCK•CEN aim at investigating a perturbation of the capacity of Boom Clay to retard the migration of radionuclides to the biosphere, after disposal of Eurobitum bituminized radioactive waste in the clay. One of the geo-chemical perturbations is related to an oxidation of Boom Clay by the large amounts of nitrate that will be released by Eurobitum. A more oxidized Boom Clay could have a lower reducing capacity towards redox sensitive radionuclides, possibly enhancing their migration. Batch tests are being performed to study whether nitrate and nitrite can oxidize the main components of Boom Clay (dissolved organic matter, kerogen, pyrite) without the mediation of bacteria, since it is not yet clear if bacteria will be active in the clay around a disposal gallery for Eurobitum. In this paper, we present the results of a first series of batch tests with Boom Clay slurries and Boom Clay water, aimed at investigating a pure chemical reduction of nitrate and nitrite.