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Dounreay. Nuclear and Chemical Land Contamination. Background. Site on north coast of Scotland set up in 1955 as UK’s centre of fast reactor development Last reactor ceased operation in 1994 Fuel reprocessing ended in 1996 Fuel fabrication ended in 2004
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Dounreay Nuclear and Chemical Land Contamination
Background • Site on north coast of Scotland set up in 1955 as UK’s centre of fast reactor development • Last reactor ceased operation in 1994 • Fuel reprocessing ended in 1996 • Fuel fabrication ended in 2004 • Construction, demolition and waste management on going • One of the most complex nuclear clean up challenges in the world
Dounreay Site Restoration Ltd • DSRL are the site licence company responsible for the closure programme of the site • Site is owned by the Nuclear Decommissioning Authority (NDA) who contract DRSL to manage the site
Main Environmental Problems • 65m deep shaft containing intermediate level waste is contaminating some groundwater • Fragments of irradiated nuclear fuel were discharged into the sea during reprocessing in 1960s and 70s • 18,000 cubic metres of radiologically contaminated land, and 28,000 cubic metres of chemically contaminated land • Large amount of highly active waste and intermediate level waste in storage • Large amount of uranium and plutonium still on site • Site is threatened by coastal erosion
Shaft • Vertical shaft built in 1950s to construct a low active effluent discharge tunnel • In 1958 authorisation given for the disposal of unconditioned intermediate level radioactive wastes • Hydrogen explosion in the shaft in 1977 caused severe damage to superstructure - material consignments to the shaft ceased • Decision to empty shaft made in 1998
Shaft Clean-up • First phase of decommissioning completed in 2008 – Hydraulic Isolation • Grouting of rock fissures reducing flow of groundwater through shaft • 400 boreholes drilled into rock and fine grout injected under pressure • Water volume reduced from 350m3/day to 12.7m3/day • Water level in shaft maintained below sea level by daily pumping of water • Reduces amount of water that can flow through the shaft and contaminate the rock on the seaward side • After grouting volume of pumped water reduced from 15m3/day to 1.3m3/day
Success of Hydraulic Isolation • Highly Commended at Ground Engineering Awards 2009 • Received Ground Engineering Award and Exceptional Performance Award at the Construction News Specialists Awards 2009 • Received Civil Engineering Award at British Construction Industry Awards 2009 • “an extraordinarily innovative and complex project delivered with extreme care, confidence and total team collaboration. “
Future Shaft Clean-up Plans • Next stage involves removal, treatment and storage of waste • Concept designs for waste retrieval, treatment and storage facilities • In March 2010, DSRL announced a delay to the construction of these facilities • Retrieval of the waste is unique among nuclear decommissioning around the world
End State of Shaft • Initial Options: • Near Field (1m radius): • Natural attenuation; removal of rock; chemical clean; passive out-diffusion; surface seal; local back-flush; local chemical back-flush • Far Field (1-300m radius): • Natural attenuation; removal of rock; flushing with water; flushing with chemicals; in-situ immobilisation • Decision will be assessed by BPEO process
End State of Site • “a restored site, with early release of land once decommissioning was complete “ • Some contaminated ground will be remediated by the end of decommissioning in 2025-32 • Other contamination will be left to decay naturally in the ground through to 2300 • Estimated cost of decommissioning - £2.6bn
Thank you for listening • This case study highlights the need for safe nuclear waste management policies particularly for the new generation of nuclear power stations.
