A Conceptual Reprocessing and Waste Management Scheme for Zircaloy-Clad Thoria Fuels

Abstract

A family of inorganic ion exchangers has been under development in this laboratory for stabilization of nuclides from various nuclear processing waste streams.1 These materials are formed from hydrous oxides of titanium, zirconium, niobium, or tantalum and have a high affinity for all polyvalent cations in the wastes and a large ion exchange capacity. They consolidate and convert to nonvolatile, leach-resistant ceramic waste forms. While their effectiveness for high-level waste stabilization was demonstrated mainly with the titanium form of the ion exchanger, the zirconium and other forms can also be used. The large source of zirconium in the form of waste Zircaloy fuel hulls offers the particu- larly interesting possibility of combining this waste stream with others to mutual benefit. In fact, there is more than enough zirconium in this high-level solid waste to stabilize all the associated (e.g., Purex) wastes in the form of stable zirconates and to simultaneously reduce the resulting high- level volume by a factor of ∼2 over the traditional calcine- glass approach. This observation has been investigated, and a conceptual process to convert this Zircaloy waste to ion exchange material was recently described.2,3 This process basically involved distillation of ZrCl4 from the chlorinated waste, followed by reaction to form alkoxides, and then hydrolysis.