The Scientific Basis of Nuclear Waste Management

Abstract

Waste is produced at every stage of the nuclear fuel cycle. While large volumes of short-lived radioactive waste are already handled by the nuclear industry in surface storage facilities, the management mode of high-activity, long-lived waste has not been decided in detail and is still under study in all nuclear countries. Scientific knowledge is in progress, technical solutions are emerging, in a context where science and technology interact strongly with social and economical issues. With a closed fuel cycle, waste management from its production to its final destination looks like a chain whose links are treatment recycling, conditioning, storage, and disposal of the final waste. With the open cycle option, the first link is absent. This chapter provides the concepts and data that form the scientific basis of nuclear waste management. Section 1 deals with the origin, nature, volume, and flux of nuclear waste, and describes the management options. Section 2 deals with waste conditioning, with special emphasis on two important conditioning matrices: cement-like materials and glass. The elaboration and long-term behavior of these matrices are treated successively. In many countries, spent fuel is considered as waste, and must be conditioned as such. A special section is devoted to this issue. Section 3 deals with waste storage and disposal. Interim storage of long-lived waste is already an industrial reality, and the design and properties of the corresponding installations are described. The final disposal of ultimate waste in deep geological repositories is more prospective, but the main concepts are described, with emphasis on the mechanisms, models, and orders of magnitude of the main physical and chemical phenomena that come into play in the long-term evolution of these installations. Finally, a short description of the methodology used to evaluate the safety of these installations is given. A simplified example of application of this methodology is given to evaluate the order of magnitude of the radiological impact of geological disposal of long-lived waste.