Intermediate level waste

Waste management strategies for ILW are currently variations on interim storage of unconditioned or conditioned (e. g., grout encapsulated, polymer encapsulated or vitrified) waste. For higher activity waste, government poli­cies for England and Wales differ from those of Scotland. ILW strategy in England and Wales is aimed at providing storage facilities prior to develop­ment of a geological disposal facility (GDF). The objective is for safe storage to be possible for 100 years or more and for the strategy to be revised if a geological disposal facility is not available by 2100. In Scotland, the policy for the long-term management of HAW is aimed at storage in near-surface facilities that are located as near as possible to the site where the waste was produced (Scottish Government, 2011). Recognising the uncertainty in future developments of the strategy for HAW, long-term monitoring and the capability of retrieval of the wastes is a requirement of the Scottish approach. Within this framework, the NDA is committed to reducing risks by dealing with higher activity wastes stored in ageing, legacy facilities and placing them into safer storage conditions.

There are currently a number of ways that ILW is stored in the UK:

• raw, untreated waste in legacy facilities;

• historically treated waste in storage that would require further treatment or conditioning before long-term safe storage could take place;

• interim storage of conditioned waste (in cement);

• waste stored in modern facilities that would still require waste conditioning;

• in-situ waste awaiting decommissioning.

ILW is being treated and conditioned ready for disposal, despite the unavail­ability of a GDF. Such treatment and conditioning is in accord with generic repository assessments undertaken by the radioactive waste management directorate (RWMD) of the NDA. The RWMD operate a Letter of Compli­ance process to advise waste producers concerning the suitability of their packaging and conditioning approaches. In general, the UK’s ILW is encapsu­lated in cement and contained within stainless steel or concrete containers (Ojovan and Lee, 2005). The Letter of Compliance process is regulated by the ONR and the environment agencies under joint regulatory arrangements.

In 2009, there were 19 modern ILW stores in the UK. The majority of the largest hazards and environmental risks posed by ILW in the UK are stored at Sellafield and Dounreay. The NDA’s strategy is focused on reducing these risks by removing wastes to newer and safer facilities (NDA, 2009). The waste is conditioned prior to storage and, as of 2008, 8% of the UK’s ILW had been conditioned, packaged and placed into interim storage (NDA, 2009 ).

The bulk of the UK’s ILW, mainly Magnox fuel cladding held in under­water tanks at Sellafield, was until recently stored in a series of 22 silos. The contaminated liquid has presented a challenge to decommissioning and retrieval of the waste. In 2010, the liquid was piped in a shielded structure over the Sellafield site to the Sellafield ion exchange effluent plant (SIXEP) processing facility, where the radioactivity was removed by filtration over aluminosilicate sand. The intention is to store this ILW in solid form, while the silos are replenished with clean water and repeatedly diluted.

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