Geopolymers as candidates for low/intermediate level highly alkaline waste.

Abstract

Geopolymers should be serious waste form candidates for intermediate level waste (ILW), insofar as they are more durable than Portland cement and can pass the PCT-B test for high-level waste. Thus an alkaline ILW could be considered to be satisfactorily immobilised in a geopolymer formulation. However a simulated Hanford tank waste was found to fail the PCT-B criterion even for a waste loading as low as 5 wt%, very probably due to the formation of a soluble sodium phosphate compound(s). This suggests that it could be worth developing a ìmixedî GP waste form in which the amorphous material can immobilise cations and a zeolitic component to immobilise anions. The PCTñB test is demonstrably subject to significant saturation effects, especially for relatively soluble waste forms.