Vitrification of High Level Waste in the UK

In the UK, highly radioactive (HA) liquor from the reprocessing of spent nuclear fuel is converted into a borosilicate glass at the Sellafield Waste Vitrification Plant (WVP) yielding a stable and durable waste form suitable for long-term storage and subsequent disposal. The WVP uses a two-stage design based on the continuous French AVH (Atelier de Vitrification de la Hague) process and as of April 2012 had produced ∼2,200 te of waste glass in ∼5,600 containers.WVP product glass is manufactured to a Quality Assured Process Specification, with an historic targeted waste oxide incorporation of 25 wt%. Recently, by using a full-scale inactive test rig to determine operational envelopes, it has been possible for the WVP to implement higher waste loadings. This will result in fewer containers being produced, which will provide considerable savings not only operationally, but also for storage, transport and final disposal.In addition to changes in Blend ratio and increased waste incorporation, future challenges for the WVP are related to post-operational clean-out (POCO) of the HA liquor storage tanks (HASTs). The waste feed arising from POCO will be enriched in certain species, e.g. molybdenum, which will limit the existing process in terms of waste loading. Hence, work is currently being undertaken to underpin the processing of POCO waste through the WVP.