An introduction to high-level nuclear waste and the concept of geological disposal

Abstract

Waste can arise at a number of points in the nuclear fuel cycle starting with the mining and milling of uranium ore, during its refinement and enrichment, in the nuclear reactor itself and as a result of the reprocessing of spent fuel. Figure 1.1 shows the main stages in the nuclear fuel cycle while Table 1.1 shows the amount of waste arising at these various stages within the context of a 1 GWy(e) light-water reactor [1]. Table 1.2 shows the approximate theoretical quantities of some of the major fission products at different times after removal from a reactor that has operated at 1 MW(e), also for one year. The many types of waste involved may be classified according to their origin, with individual reactor types as shown in Table 1.3 giving rise to wastes with different detailed characteristics. Table 1.4 shows the varying nature of the radioactive liquid wastes arising from different reactor types. Wastes can also be classified by reference to their physical state and to their various levels of radioactivity and radiotoxicity. Knowledge of these various characteristics is required in order to assess the likely hazard posed by any particular waste and to determine the best method of long-term disposal.