From the start of active operations at Dounreay, the site has managed its radioactive waste in its own waste management facilities.

LLW

Alone amongst UK nuclear sites, it has disposed of its LLW to near-surface disposal pits on site instead of sending the packaged LLW to the LLWR. A series of six disposal pits were constructed and operated from 1959 until 2005. These are situated at the north end of the site adjacent to the sea and contain around 33,000 m3 LLW. Pits 1-4 are unlined and accepted tumble tipped bagged LLW. Pits 5 and 6 have concrete bases and the LLW was disposed of in uncompacted or supercompacted 200 litre drums. All the pits contain large bulk items and are now capped off with rock and soil. Water ingress to the pits is collected in sumps and pumped to the LLLE treatment plant.

During the 1990s, it was clear that further extension of the existing LLW disposal facility was impracticable and would not meet current environmen­tal regulatory requirements. In 1999, a best practicable environmental option (BPEO) study (UKAEA, 2004a) was initiated to determine the most appropriate way in which to manage the continuing operational LLW and LLW that would be generated from decommissioning the whole site (approximately 150,000 m3 of packaged LLW). The BPEO study included significant stakeholder involvement (Broughton and Tait, 2008; Broughton, 2003). Preliminary performance assessment work and environmental impact studies (UKAEA, 2004b) were carried in parallel to inform the BPEO study. Eventually this led to the BPEO being identified as the construction of six new disposal vaults on the Dounreay estate south east and inland from the licensed site boundary. Their positioning was influenced by 10,000- year sea level rise assumptions. The BPEO proposal was endorsed by the Scottish Government Environment Minister in May 2005 (Scottish Execu­tive, 2005) and the planning application for this development was granted by the Highland Council in January 2009 (Highland Council, 2009). The project to construct the first two of the new vaults and associated facilities is currently in progress with the target of bringing them into operation in 2014. The vaults are of concrete construction with steel roofs and extend 15 m below ground level. Comprehensive water management features are included. The LLW will be disposed of in grouted half-height ISO contain­ers (HHISO) placed in one of the new vaults. Decommissioning waste of very low activity, but high volume (DLLW) such as concrete, rubble and steel will be disposed of in the other new vault in a designated bulk manner.