Offshore monitoring
It is generally accepted that the source of particles now turning up on beaches is coming from the seabed. Offshore monitoring undertaken since 1997 has helped to determine the extent of the contamination.
Computer modelling: To better understand the dynamics of the Pentland Firth and how particles would travel in that environment 3D computer modelling was developed. Surveys of the seabed subsequently validated parts of the model.
Offshore monitoring: Since 1997, offshore monitoring and mapping surveys have continued. Using divers to detect and retrieve particles was undertaken until technology moved on with the development of a remotely operated vehicle which eliminated any potential diving risk. For more information click here.
Offshore survey reports: Reports on the offshore surveys are available here.
Technology improvements: Technology has come a long way since diving operations began and the remote operated vehicle (ROV) has been developed. Trials for retrieval capability is underway with two systems being tested.
Monitoring the seabed
A programme of radiological surveys of the seabed has and continues to be carried out.
Diving surveys in recent years of inshore waters close to Dounreay validated some areas of the model, with over 900 particles detected by hand-held probes in areas of the seabed from Sandside in the west to Brims Ness in the east. Particles found by divers were recovered and returned to Dounreay.
An intensive research programme led to the development of a new remotely operated vehicle (ROV) which has the advantages of operating in deeper water (>25m), covering the seabed faster than divers and removing the need for diving activities.
When the ROV was deployed it did not have the capability of retrieving particles. However the valuable data collected by the mapping of particles has allowed a clearer view on the extent of the contamination.
The remotely operated vehicle is deployed from a surface vessel and can map the location of particles continuously for up to 10 hours per day. Its performance was validated against divers in 2005.
The programme of work in 2006 was focussed on identifying whether particles were present in areas of the seabed predicted by a computer model of sand movement and to confirm the absence of particles in other areas where the model did not predict their presence. Particles in the marine environment are believed to behave in a similar way to grains of sand.
Particle mapping survey carried out in 2007
Map of offshore finds
