The effect of cement additives on radionuclide solubilities

A range of commercial products can be added to cements and concretes in ord er to modify their properties. These admixtures may be used in cementitious materials employed in the construction and backfilling of a radioactive wa ste repository vault. Many admixtures contain organic materials and it is k nown that some organic compounds can alter the solubility and sorption beha viour of radionuclides in a repository. In this work, the effects of two Ja panese cement additives on the solubilities of technetium, uranium, plutoni um and americium at pH 12 have been studied. In some cases, radionuclide so lubility enhancements in excess of two orders of magnitude were observed in the presence of additives. This can be interpreted in terms of the formati on of radionuclide/hydroxy/additive complexes.