Dounreay clean-up moves offshore
3 May 2012
Work to clean up radioactive contamination that leaked from Dounreay more than two decades ago is set to move offshore this month.
Radioactive fragments of irradiated nuclear fuel were released into the sea from the Dounreay nuclear plant in Caithness during the 1970s.
These fragments are located in a plume that is spread over 60 hectares of seabed from a disused discharge point 600 metres offshore. The main plume is equivalent in size to 600 Olympic-size swimming pools.
To date, more than 1800 fragments have been recovered from the seabed. This year’s work is expected to complete coverage of the plume by remotely-operated vehicle (ROV).
A 1500-tonne barge will be moved into position above the plume later this month and will work continuously until late summer. The ROV will be lowered into water up to 35 metres deep and driven over the seabed at 1mph.
Engineers hope that radiation detection equipment on the ROV will detect higher activity fragments buried at least 50cm deep in the sediment.
Senior project manager Bill Thomson said: “The planned work includes some repeat coverage, providing us with valuable data about repopulation rates, caused by sediment movement, and the efficiency of the clean-up system.”
“We’ll be providing real-time data to the independent experts who sit on the advisory group and who advise us and the Scottish Environment Protection Agency (SEPA).”
In 2011, the Scottish government admitted that the radioactive contamination will never be completely removed. SEPA said that returning the seabed near the plant to a “pristine condition” could do “more harm than good.”
However, Dounreay has seen a flurry of activity in recent months. In April a group of 25 engineers successfully neutralised the liquid metal coolant from the primary circuit of Dounreay’s experimental fast reactor.
This was the second highest hazard removal on the Nuclear Decommissioning Authority’s (NDA’s) estate- the highest being Sellafield.
To read decommissioning manager Mike Brown’s account of dealing with one of the most hazardous legacies of Britain’s atomic research, please pick up the next issue of Process Engineering.
