Leaching behaviour of and Cs disposition in a UMo powellite glass-ceramic

A UMo powellite glass-ceramic designed by French workers to immobilise Mo-rich intermediate-level waste was found to be quite leach resistant in water at 90 C with the dissolution of Cs, Mo, Na, B and Ca not exceeding 2 g/L in normalised PCT tests. ¹³³Cs solid state nuclear magnetic resonance and scanning electron microscopy (SEM) showed the Cs to inhabit the glass phase. The microstructures were not greatly affected by cooling rates between 1 and 5 C/min or by introducing 10 times as much Cs and Sr. Protracted leach tests at 90 C showed surface alteration as evidenced by SEM and particularly transmission electron microscopy; the main alteration phase was a Zn aluminosilicate but several other alteration phases were evident. Voidage in the alteration layers was indicated from enhanced lifetimes in positron annihilation lifetime spectroscopy.