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Seabed particle clean-up underway

August 26, 2008

The remotely-operated vehicle being used by Fathoms to retrieve particles

A new phase in the clean-up of Dounreay is underway with the start of underwater operations to demonstrate the use of remote equipment to remove particles from the seabed.

Independent experts estimate there may be 1500 fragments buried in the sediment close to the site’s old discharge outlet that are a significant hazard to public health. The disintegration of these fragments is believed to contribute to the number of smaller, less hazardous particles found on local beaches.

The start of work to recover these fragments from the seabed follows several years of research and the largest public consultation in Dounreay’s history.

Wick-based offshore contractor Fathoms Ltd has been contracted to carry out the work following a competitive tendering exercise and offshore trials.

Fathoms is deploying a remotely-operated vehicle capable of detecting and retrieving particles buried up to 50cm deep in the sediment. The ROV is controlled from a surface vessel where recovered particles are separated from the sediment and packaged for return to Dounreay.

Weather permitting, the ROV can cover up to 4,000 sq metres per day, although this may not be achieved if a large number of particles are detected. The first phase now underway until the end of September is expected to provide further information on the effectiveness of the system and is expected to permit the planning of further seasons of full-scale operation. Weather conditions effectively limit the period of operation to May-September each year.

The overall clean-up is targeted at an area of seabed measuring 60 hectares, which is equivalent in size to 60 or so football pitches. This is in the vicinity of a fisheries exclusion zone imposed over a 2km radius from the old seabed discharge outlet.

Monitoring of local beaches is continuing during the clean-up and special attention is being paid to any change in the frequency of onshore finds. Disturbance of the seabed means a short-term increase in beach finds close to Dounreay cannot be ruled out.

Fathoms Ltd is carrying out the work for Dounreay Site Restoration Ltd, the site licence company contracted by the Nuclear Decommissioning Authority to clean up and close down Dounreay.

DSRL managing director Simon Middlemas said: “The start of seabed clean-up heralds an important new phase in the site closure programme. We’ve made significant progress in recent years to clean-up and dismantle the site itself. Now we are cleaning up off-site a legacy that has cast a shadow over the site for too long.”

Phil Cartwright, particles clean-up project manager, said: “The public consultation process recognised that recovery of every particle, irrespective of risk, was impractical but did find support for retrieval of those particles that pose a significant risk to health.

“That is the option we are now putting into action. We expect to detect a number of smaller, less radioactive particles as well and these will also be retrieved.

“We have worked very closely with independent experts in the Dounreay Particles Advisory Group, the Scottish Environment Protection Agency and many others, including affected land-owners, to reach the stage where we can clean up the seabed in a way that is environmentally and publicly acceptable. I would like to thank them for their co-operation.

“We will continue to work closely with regulators and all interested parties during the clean-up phase to evaluate its success and adjust the programme, such as the frequency of onshore monitoring, as necessary. We will also report finds and performance on a weekly basis via our website at www.dounreay.com.”

The estimated cost of the clean-up and continued beach monitoring until the early 2020s is £18-25 million.

Click here to learn more about particle clean-up.

 

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