This contribution addresses various aspects of nuclear waste vitrification. Nuclear wastes have a variety of components and composition ranges. For each waste composition, the glass must be formulated to posses acceptable processing and product behaviour defined in terms of physical and chemical properties that guarantee that the glass can be easily made and resist environmental degradations. Glass formulation is facilitated by developing property-composition models and the segregate foam may hinder heat transfer and slow down the process molten salts may accumulate in container refractory walls: on cooling, the glass may precipitate crystalline phases. These problems need targeted exploratory research. Examples of specified problems and their possible solutions are discussed.
