Rodney Ewing1

1, Stanford University, Stanford, California, United States

Over the past thirty years, there has been a considerable amount of research on nuclear waste forms of all types: glass, crystalline ceramics, composite ceramics and spent fuel. Most recently, the idea of structural hierarchies has been used to identify new waste form materials. I will briefly survey the history of waste form development and discuss new challenges for the future. One of the very unique aspects of waste form research is the need to develop a means of predicting materials behavior over hundreds of thousands of years. There are a number of approaches: experimental, computational and the use of natural systems that must converge in order to build confidence in these long-term predictions. More recently, there have been discussions of matching the waste form to the characteristics of the waste stream or of selecting waste forms whose durability is compatible with the geochemical and hydrologic conditions in a geologic repository. In both cases, the nuclear waste form adds value to the safety assessment of a geologic repository.