The Solubility Limited Source Term for Cement - Conditioned Wastes: A Status Report

AbstactAn important function of the cement backfill in a nuclear waste repository is to react with aqueous waste species and reduce their solubility. However, to quantify backfill performance it is first necessary to prove the existence and establish the nature of the chemical solubility controls. This can be done by characterising the solubility-limiting phases, determining their solubility and thermodynamic functions, and assessing their stability and persistence and solubility during backfill degradation. Much of the necessary data must be acquired experimentally. The title paper describes briefly the progresss of experimental work on selected species including nickel, chromium(III,VI), tin(IV) molybdenum(VI), uranium(VI), Ce(III,IV), thorium, actinide simulants (III, IV) and chloride. Data needs are assessed and although much experimental work remains to be done, methodologies have been developed which will expedite progress. The expectation of a more quantitative performance assessment of cement barriers is, therefore, attainable.