TITANATE CERAMIC PHASES FOR SURPLUS PLUTONIUM IMMOBILISATION

A multi-phase pyrochlore-rich titanate ceramic has been chosen by the US Department of Energy for the immobilisation of surplus military plutonium. The pyrochlore-rich wasteform was designed to have a high capacity for plutonium, uranium and neutron absorbers such as hafnium and gadolinium as well as tolerance for high impurity loadings from the plutonium feed stocks. More than 99 wt % of the plutonium is distributed among the pyrochlore, zirconolite and brannerite titanate phases that make up the multi-phase wasteform. This paper presents the results of our current studies on the preparation and characterisation of single phase Pu or U containing specimens of the three major titanates prevalent in the pyrochlore-rich ceramic wasteform. The results cover aqueous durability, radiation damage sensitivity and natural mineral analogues of the above titanates.