The Drigg site has been in operation as the national facility for the disposal of LLW since 1959. Disposals until the late 1980s were solely by tipping essentially loose wastes into excavated trenches. More recently, trench disposals have been phased out in favour of emplacement of containerized, conditioned wastes in concrete vaults. For items of waste too large to be size-reduced and packed into containers, in-vault grouting is carried out. The previous trench disposal facilities have been capped. The profiled earthen cap incorporates an impermeable membrane to minimize rainwater penetration. Monitoring of the environment demonstrates that the site's impact is negligible. Reduction in volumes of LLW for disposal resulting from waste minimization initiatives and the high force compaction of all compactible arisings has led to a review of the design of future vaults. Future disposal capacity is now based on modular vaults each of about 50 000 m~3 capacity. These will be supplemented by in-vault grouting cells. These facilities together with residual space in the current vault will provide a future disposal capacity of about 800 000 m~3. The radiological capacity of the site has been based on a post-closure risk assessment. On the basis of information in the UK Radioactive Waste Inventory, future arisings of wastes have been estimated and compared with the site's volumetric and radiological capacities. This has shown that the Drigg site should be able to accept essentially all UK LLW arisings to the middle of the next century, provided that a system of waste stream controls is operated to limit additional demands on radiological capacity from high specific activity streams, such as might arise from the reclassification of ILW to LLW either as a result of reassessment or decontamination.
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