Another former RAF site, Dounreay, became the centre for the UK’s fast reactor research and development in 1954. Commercial energy production began in 1962 becoming the first fast reactor in the world to supply energy to the grid. However, fast reactor technology proved to be more expensive than was first thought and consequently all fast reactor programs ceased operations in 1994. Reprocessing and fuel fabrication operations ended in 1996 and 2004, respectively. Dounreay is now wholly a decommissioning site owned by the NDA and run by Dounreay Site Restoration Ltd. The site closure program is scheduled to be completed by 2025 at an estimated cost of £2.6 bn. Over the course of decommissioning, Dounreay is expected to generate a lifetime waste of 97 126m3 of LLW, 3164m3 of ILW and 0m3 of high level waste (HLW).12 Dounreay has a legacy of irradiated nuclear fuel particles which were dis­charged into the sea as a result of reprocessing activities during the 1960s and 1970s. These particles have been detected on the seabed around Dounreay with the most hazardous fragments located close to the old discharge point on the seabed. Their disintegration is believed to be the source of smaller, less hazardous particles detected on local beaches. Around 1000 significant (106 Bq of 137Cs), 1000 relevant (105 to 106 Bq of 137Cs) and 3000 minor (< 105 of 137Cs) particles are thought to be present within the main particle plume offshore from Dounreay.13 Monitoring of the particles is expected to last until 2020s and with a total cost estimated at £18-25 million.

On site, there are pockets of caesium-137 contamination with activities greater than 4Bqg-1, although the majority of contamination over the site is below 0.4 Bqg-1.14 Between 1959 and 1971, solid ILW was disposed of in the Dounreay waste shaft. A purpose built wet silo was constructed in 1971 as an alternative to the shaft after which solid ILW was tipped into the silo, a large underground concrete vault filled with water. Large items too big for a purpose built wet silo continued to be disposed of down the shaft until 1977, when an explosion in the airspace above the water column damaged the shaft cover. There are uncer­tainties over the exact contents of the shaft, thought to include contaminated equipment, chemicals, natural uranium fuel, radioactive sources and sludges.15 A total of 703 m3 of waste is covered by a water column 8 m deep which is below sea level so that groundwater flow is towards the shaft.

Management of Land Contaminated by the Nuclear Legacy