Has the full extent of the contamination of the seabed been mapped or could other pockets of particles in the offshore sediment remain to be detected?
There is a massive area of sand seafloor which could be mapped by a remotely operated system. Realistically only a small proportion of this area can be mapped each year using the available systems. The sampling strategy adopted was intended to provide information on the spread of offshore particles, and has used transects from shallow water to deeper areas to identify the ‘edge’ of the main particle plume. Other areas further from Dounreay have been checked but have not resulted in further particle finds. The geographical extent of particles on the seabed was reported in DPAG’s Third Report and updated in DPAG’s Fourth Report. All survey results to date, either by divers or by remotely operated vehicles, indicate that the more radioactive particles (which are generally physically larger) are deeply buried in sand and the majority of these have not moved beyond about 1km from the release point.
