Particles and beaches

What are particles?

Particles are small, radioactive fragments of nuclear fuel that have been irradiated in a reactor.

How were they created?

About 80 per cent came from materials test reactor fuel elements. The fuel was 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 the 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 enhanced 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 estimates there may be in the region of five thousand particles remaining in the offshore sediment close to the plant today.

Are they still being released?

No. Although there are known sources of particles on the site, no credible routes for their continued 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. "Relevant "and "minor" particles have been found on three beaches used by the public – Sandside, Murkle, and Dunnet.

Sandside is the only beach where particles are found regularly (see table below). Particles, including "significant" particles, have been found on the enclosed foreshore at Dounreay.

How did they get there?

They are carried to the beaches by the waves and tide from the sediment near the old seabed discharge point. Seabed surveys indicate the main flow is to the east, with a westward flow that has been assessed towards Sandside.

How dangerous are they?

All 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. Dounreay Particles Advisory Group has recommended formal closure of the foreshore.

In its Third Report, the group classified particles on the basis of their health risk – "significant", "relevant" or "minor".

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, subject to the permission of land-owners, and retrieval of particles following detection reduces the risk.

Fishing is banned in the area near Dounreay where the most hazardous particles have been found.

What are you doing to clean it up?

Following the biggest public consultation in Dounreay’s history, the first phase of seabed clean-up got underway in August 2008. During this initial demonstration phase, 55 particles were recovered.

How long will the clean-up last?

Remotely-operated devices will be deployed over several summers to remove the most active particles from an area defined in “population maps” produced by Dounreay Particles Advisory Group. This will be followed by a number of years of monitoring local beaches. We will review progress with SEPA and report regularly to the public.

We expect to complete the offshore work as quickly as the technology, weather and funding allow. Our current expectation is that onshore monitoring is reviewed regularly with SEPA and land-owners, with cessation possible in the 2020s.

How much will it cost?

We estimate £18-25 million.
 

Summary of particle funds up to November 2008
  Melvich Sandside Offshore Dounreay Crosskirk Brims Scrabster Thurso Murkle Dunnet
Total - 117 989 256 - - - - 1 1
Significant - - 248 161 - - - - - -
Relevant - 21 270 70 - - - - - -
Minor - 96 471 25 - - - - 1 1

Public restrictions

 - - Fishing prohibited Access limited - - - - - -
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