Kinetics of UO2 dissolution under highly alkaline conditions: application of a thin film continuous flow-through reactor

Abstract

The treatment and management of nuclear waste keeps generating technical and ethical problems nowadays, being one of the most important environmental challenges. Due to this problem, international organizations have seen in the concept of deep geological disposal, materialized in Deep Geological Repository (DGR), the most viable and safe way to give a permanent solution to this problem. Multibarrier containment of DGR will eventually fail and tens or thousands of years later, groundwater,which is the only likely vector that may transport radioisotopes back to the biosphere, may contact the spent nuclear fuel (SNF). Consequently, SNF itself is the last barrier to offer resistance to the action of water. In this project, the effect of cementitious waters, from the construction of DGR, on the kinetics of dissolution of uranium dioxide (UO2) has been studied. UO2 has been used as a chemical analogue of SNF. This type of water leads to highly alkaline conditions with presence of silicate (SiO3 2- ) and calcium (Ca2+ ). Moreover, the influence of carbonate (CO3 2 ) present in groundwater has been studied. A continuous thin film flow-through reactor system has been used for the quantifica