The UK’s Atomic Energy Authority (UKAEA) has pleaded guilty to four charges related to the disposal of radioactive waste to a landfill site at Dounreay between 1963 and 1975.
The charges, under the Radioactive Substances Act 1960, also concern the release of particles from the site to the environment between 1963 and 1984. Eighty per cent of particles found to date have been from materials test reactor fuel elements that were dismantled in water-filled ponds before being transferred to an acid dissolver for reprocessing – chemical separation of the waste from the re-usable material.
This involved removing excess material from the edges of the elements and resulted in accumulations of metallic swarf in the ponds, some of which contained fragments of the irradiated fuel.
The authorised disposal route for contaminated swarf that accumulated in the ponds was to the waste shaft and silo at Dounreay. However, during cleaning of the ponds, which involved draining the water, some of this swarf entered the low-active liquid effluent drainage system which discharged to sea.
Speaking outside the Wick Sheriff Court following the case, UKAEA director of safety Dr John Crofts said: “We have pleaded guilty to all four charges which relate to events in the early years of the site,” acknowledging that “some mistakes were made.”
Crofts added that the practices which gave rise to the particles ceased long ago and the UKAEA is now focussed on remediation of the site and the particles issue.
Dounreay has started drilling up to 400 boreholes around the 65m deep waste shaft and grout will be injected through the boreholes to seal fissures in the rock to create a giant containment barrier in the shape of a boot around the shaft that will isolate the radioactive waste from groundwater.
The project – the first of its kind in the world – will prevent large volumes of groundwater flowing into the shaft during waste retrieval and becoming contaminated. It will also reduce the risk of leakage from the shaft in the interim.
The work is being carried out by UKAEA on behalf of the Nuclear Decommissioning Authority and follows agreement by regulatory authorities.
Isolation of the shaft has commenced four years earlier than previously planned and is expected to take between two to four years to complete. The £16 million ($32 million) isolation contract was awarded to Ritchies, the specialist geotechnical division of Edmund Nuttall Ltd, and the total cost of this phase of the shaft decommissioning is £27 million ($54 million).
Dounreay was Britain’s centre of fast reactor research and development from 1954 until 1994. The site is now closed and in the process of being demolished with decommissioning due to be complete by 2033.
In related news Norman Harrison, currently acting chief operating officer for the UKAEA, has been appointed as the new chief executive officer with effect from 1 February 2007. He became acting chief operating officer in August 2006.
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