Particle Clean-up
An important part of the work to close down Dounreay is to address its legacy of radioactive particles found in the marine environment around the site.
In August 2008, Dounreay Site Restoration Ltd started to clean up the seabed where the most hazardous of these particles are to be found. This continued in the summer of 2009, when more than a hundred particles were retrieved from the seabed.
Particles are fragments of irradiated nuclear fuel discharged to sea as a result of practices in reprocessing during the 1960s and 70s. The most hazardous fragments are located close to the old discharge point on the seabed and their disintegration is believe to be the source of smaller, less hazardous particles detected on local beaches.
The start of seabed clean-up followed extensive research and public consultation about the best practicable environmental option for dealing with the legacy.
This identified the retrieval of particles from the area of seabed where the highest activity particles have been found and where the particle population density is at its highest, with on-shore monitoring specifically at Dounreay foreshore and Sandside beach, as the preferred way forward.
Main plume remediation area
Click here to see a larger version of the above image
The start of the particle retrieval operation by remotely-operated vehicle heralds a positive step by Dounreay to deal with this major off-site legacy. It is undertaken as part of the Nuclear Decommissioning Authority’s site closure and clean-up programme at Dounreay.
At a glance
| Clean-up area | 60 hectares |
| Depth of water | Up to 30 metres |
| Estimated number of significant particles | 1500 |
| Maximum speed of clean-up vehicle | 0.6 metres per second |
| Detection depth in sediment | 50 cm |
| Coverage | Up to 4000 square metres per day |
| Initial length of clean-up | 3 years (May-Sep) |
| Number of public beaches monitored | 7 |
| Duration of monitoring | 2020s |
| Total cost | £18-25 million |
Trials of the retrieval system indicated that disturbance on the seabed is minimal and likely to be much less than natural forces during storm conditions. However, following discussions with the independent expert group Dounreay Particles Advisory Group, it was decided to include the monitoring of an area of seabed on the edge of the fishing exclusion zone, to allow the effect of the seabed recovery to be checked in advance of seeing an increase or decrease in particle numbers or activities at nearby Sandside beach. A similar area to the east of the retrieval operations has not been planned at present, but this will be kept under review.
The retrieval operation is starting now as the collection of evidence on the particle population and improved understanding of health effects has enabled the definition of a fairly limited area of the seabed where the highest activity and hence the particles with the greatest health risk are located. Fishing has been prohibited in this area since 1997.
The development of detection equipment with retrieval capability means we are now able to systematically cover the seabed, retrieving particles as we progress.
The offshore retrieval work is accompanied by continued monitoring on-shore. The Dounreay foreshore, being closest to the area where the offshore work will happen, is likely to be the first area to see a change in particle arrival rate, although it is noted that particle finds on the Dounreay foreshore do not seem to follow a pattern and may be linked to the sea conditions.
Monitoring on Sandside beach throughout the offshore retrieval period is planned. In addition, an offshore area on the plume towards Sandside will provide an early indication of a change in the particle population. The offshore retrieval work will initially be undertaken to the east of the original discharge point.
High activity particles disturbed by the offshore work are likely to remain close to their original location as more significant disturbance is likely to occur during winter storms, but this does not cause these higher activity particles to move quickly. The only place where particles of significant activity have come ashore is on the Dounreay foreshore.
DSRL regularly updates a list of all particles detected around the site. Click here.
Latest news:
- Clean-up removes 29 "significant" particles from seabed - August 2009
- Survey detects contamination on proposed waste disposal site - August 2009
- Particle found at site of proposed Dounreay low level waste facility (SEPA) - August 2009
- Offshore clean-up set to resume - June 2009
- Dounreay welcomes expert report on particles - November 2008
- Seabed particle clean-up underway - August 2008
Particle clean-up video (Autumn 2008)
Fact sheet (April 2008)
Beaches monitoring (April 2008)
Media brief (November 2008)
The clean-up machine gets ready to descend to the seabed to resume its search and retrieval of particles
Sifting through sand and sediment to retrieve a particle on board the recovery vessel
Map of offshore finds
Divers surveyed the seabed since 1997, mapping the extent of pollution and retrieving particles, before seabed clean-up started in 2008
Monitoring of local beaches continues during the offshore clean-up
Laboratory examination of a particle recovered from a beach
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