Molybdenum in nuclear waste glasses - Incorporation and redox state

The composition and structure of the mixed metal molybdates that can form in simulated high level nuclear waste (HLW) glass melts have been studied. It was found that molybdates of a tetragonal scheelite type were formed upon heat treatment of the simulated glass samples (representative of the slow cools experienced by the real vitrified product), and that these compounds are capable of incorporating the majority of the mono, di, and trivalent cations that would be present in a real HLW glass. In addition, it has been shown that altering the redox conditions prevailing upon melting can promote or suppress crystallisation in simplified model waste glasses that contain molybdenum. Experiments to investigate the effect of redox conditions during melting of simulated HLW glass on molybdate formation are also reported.