Dounreay’s site closure programme is moving offshore and up a gear to recover more radioactive waste from the seabed.
A floating platform has anchored in position 600 metres offshore to begin tracking down fragments of nuclear fuel buried in the sediment using a remotely-operated underwater vehicle.
The ROV is expected to search an area of seabed equivalent to 17 international football pitches, or 12.5 hectares, during the summer weather window.
Last year, during a smaller scale clean-up operation, more than 100 particles were lifted from an area around a disused effluent outlet.
This year’s operation has been scaled up. A larger ROV with a wider scan is being deployed. It is controlled from an offshore platform with its own living quarters, instead of a small workboat.
Their staff make up a team of 22 working around the clock in shifts on board the platform, the 60m-long barge LM Constructor .
The underwater ROV – similar in size to a small bull-dozer – is working in waters up to 30 metres deep. It is piloted from a control room on board the platform using an umbilical cable 500 metres in length.
Radiation detectors attached to the ROV are an underwater version of the Groundhog Evolution 2 system developed by Nuvia and used routinely to monitor beaches near Dounreay.
The LM Constructor was towed north from its home port of Liverpool by the Lerwick-based tug Voe Chief. Also taking part in the operation is a pilot boat, the Whitehaven-registered Tiger.
“This is a step up from previous offshore recovery operations and underlines our determination to get on with the clean-up of the seabed as part of the site closure,” said Bill Thomson, project manager at Dounreay Site Restoration Ltd, the contractor closing down the site on behalf of the Nuclear Decommissioning Authority.
The offshore platform has been used before in support of the nuclear industry, such as a three-year project to decommission a seabed outfall at Sellafield.
The seabed pollution has been traced to discharges from the site at the height of nuclear fuel reprocessing in the 1960s and 70s. It is believed to be the source of smaller particles detected routinely on local beaches.
DSRL is working with independent experts appointed by the Scottish Environment Protection Agency to assess the effect of seabed clean-up and its mitigation of the pollution. Based on current forecasts, DSRL aims to complete the remediation work by the 2020s at an estimated total cost of £18-25m. The total cost of site clean-up is an estimated £2.6 billion.