Cements in Radioactive Waste Disposal

Abstract

Depending on their radioactive content and abundance of long-lived radionuclides, radioactive wastes are often described as low, intermediate or high-level. Cements play a major role in the engineered structures, existing and planned, of most national programs for low- and intermediate-level (ILW) radioactive wastes. Final disposal of ILW is usually by burial at considerable depth (>250 meters), e.g., in planned repositories in clay at Mol (Belgium), in salt at Gorleben (Germany), and in volcanic tuffs at Sellafield (United Kingdom). A sample disposal concept is shown in Figure 1. Shallow land burial is also employed, mostly for low-level wastes (LLW) and often in concrete-lined vaults, e.g., at Drigg (UK) and Center de la Manche (France). Cements are likely to be used in a waste repository as structural elements in the engineered structure and for encapsulation of the actual waste itself (see Figure 1). In the UK, cements are also the favored material for infilling of the vault space (backfilling), and sealing.LLW and ILW are characterized by considerable heterogeneity, and comprise liquids, solids, floes, sludges, exchange resins, and contaminated laboratory equipment. Cements are capable of converting most of these waste streams into solid and stable monoliths that can be further encapsulated in a steel or concrete container. Such a product is ideal for interim storage, transportation, and final emplacement in a repository. The technology of cementation is well-established, and suited to automation and remote handling (thereby reducing the radiation dose to workers).