Particles
What are particles?
Particles are small fragments of nuclear fuel that have been irradiated in a reactor.
How were they created?
About 80 per cent came from fuel elements removed from reactors and taken to plants at Dounreay where they were broken up in underwater tanks, or ponds, before being recycled in a chemical process known as reprocessing. The dismantling process created these particles. Other particles were produced during the dry examination and preparation of other fuels for reprocessing.
How did they get into the environment?
The particles were transferred to the radioactive drainage systems on the site when the pond water became dirty and the water was drained. The drainage system discharged to the sea via sentencing tanks. Other particles were released during the transfer of solid wastes around the site and through the management of water used in these facilities.
When did this happen?
There is evidence that most of this happened until the 1970s when the numbers being created probably reduced as the design of elements improved and more modern dismantling techniques developed. Filters were fitted to the pond outlets in the 1980s. Reprocessing ceased in 1996.
How many were released?
The precise number is not known. Based on diver finds and surveys of the seabed around the site’s discharge point, Dounreay Particles Advisory Group have calculated that an estimated five thousand particles remain in the sediment today close to the plant today.
Are they still being released?
No. Although there are potential sources of particles on the site, no credible routes for their release have been identified.
How big are they?
Particles are similar in size to grains of sand.
Where else have they been found?
A number of beaches to the east and west of Dounreay have been checked. Particles have been found on three beaches used by the public – Sandside, Murkle, and Dunnet. In addition, particles have been found on the enclosed foreshore at Dounreay.
How did they get there?
They are carried by the waves and tide from the area of the discharge point to the beaches. Seabed surveys indicate the main flow is to the east, with a smaller flow towards Sandside in the west.
How dangerous are they?
All the particles found to date on beaches used by the public have contained radioactivity at levels unlikely to cause any discernible health effects if a member of the public came into contact with one. Higher activity particles have been found on the seabed and the foreshore at Dounreay and these would pose a significant health risk.
What measures are in place to protect the public?
Independent experts have assessed the risk to beach-users and found it to be low, so the beaches remain open to the public. Regular monitoring and retrieval of particles following detection reduces the risk. Fishing is banned in the area where the most hazardous particles have been found.
What are you doing to clean it up?
Following public consultation, the is planning to begin cleaning up the most polluted areas of seabed in summer 2008.
How long will this take?
Several summers of clean-up using remotely-operated devices scouring the seabed will be following by a number of years of further monitoring of local beaches. We will report to the public regularly. Based on the expected performance of the clean-up equipment, we expect to finish this work in the 2020s.
How much will it cost?
We estimate £18-25 million.
