The investigation of aluminium wastes encapsulated in the individual phases of Ordinary Portland Cement

The storage of expended radioactive wastes is one of the most costly aspects of nuclear energy due to the social and political concerns over environmental and safety issues. Immobilisation of radioactive wastes is carried out to allow them to be handled and stored safely. Currently, Ordinary Portland Cement (OPC), blastfurnace slag (BFS) and pulverised fuel ash (PFA) are used as an encapsulation matrix. The high pH of the cement system limits the solubility of many of the radioactive nuclides present. However, corrosion can occur under these conditions, particularly for aluminium. The products of corrosion, hydrogen gas evolution and expansive hydroxides can lead to poor wasteform quality which raises questions about the environmental and safety issues of cemented wasteforms. This work aims to gain further understanding of the corrosion of aluminium simulant wastes within cement matrices by separating the complex OPC system into easy-to-define pure systems. Therefore, the pure phases, tricalcium silicate, dicalcium silicate, tricalcium aluminate and tetracalcium aluminoferrite are synthesised and the corrosion of Al studied. As a result, a comparison between corrosion in OPC and pure phases can be drawn to provide fundamental information on the governing mechanisms of the corrosion reactions.