Frequently Asked Questions
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What do you mean by significant, relevant and minor particles?
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What safeguards are in place to ensure that the decommissioning cannot lead to further release of radioactive particles?
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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?
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Why has monitoring the seabed for particles been limited a certain area?
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Why is the FEPA zone for the control of fishing and the collection of seafood limited to a 2km radius?
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Are new particles continuing to arrive at Sandside beach or have they been on the beach for sometime and you are only just finding them?
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If new particles continue to reach the beaches in the future from offshore, what is the expected frequency?
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Should bay shallows and the beach areas wetted by the tides also be monitored for particles so that new arrivals may be detected and removed at the earliest opportunity and, if so, with what frequency?
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What is the possibility of particles being blown inland or being washed into the dune systems at beaches during storm conditions and what arrangements are in place for monitoring above the intertidal level?
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Are there any health and safety risks for workers to consider when clearing debris deposited by storms?
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Are small particles, which may not be detected by current survey equipment, of concern for health, particularly if suspended in the air by the action of the wind?
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Could a particle become lodged for long enough in a sensitive part of the body, such so that adverse health effects could be caused?
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Is it safe for children to play on the beaches, to build sandcastles and to paddle in the sea?
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What are the typical specific activities of the radioactive particles found to date in the marine and coastal environment at Dounreay?
What are particles?
Particles are small fragments of irradiated material that were created during the mechanical and chemical phases of reprocessing irradiated fuel at Dounreay. Reprocessing ceased in 1996 and the plants are now being decommissioned.
What are the different types of particles?
There are four distinct types of particles:
- Materials Test Reactor (MTR)
- Dounreay Fast Reactor (DFR)
- Stainless Steel particles
- Uranium oxide particles
These are different from tarry agglomerates which are decomposed organic material containing radioactivity.
The majority of particles found are MTR particles, followed by DFR. A very small proportion are stainless steel with even fewer uranium oxide particles.
How big are they?
Most are similar in size to a grain of sand. As a rule of thumb, the smallest particles, in size and radioactivity (minor), are the least hazardous and the largest ones the most hazardous (significant).
What happened to them?
Particles were discharged into the sea via the active discharge pipeline and some were lost into other drains as a result of operational standards in the early years of the site.
With the benefit of hindsight, it is now understood that the release of particles into the environment was inevitable with the systems in place during the early years of operation. Today additional equipment would be used to further reduce the probability of particle discharge.
How many particles were released into the environment?
Estimates of the total number are uncertain and may never be known. The Dounreay Paritlces Advisory Group (DPAG), in its Third Report, estimated that about 1000 significant, 1000 relevant and 3000 minor particles remain within the main particle plume offshore from Dounreay.
What is DPAG?
The Dounreay Particles Advisory Group (DPAG) is an independent body set up by UKAEA and the Scottish Environment Protection Agency (SEPA) in May 2000 to provide independent scientific advice on the particles issue.
What do you mean by significant, relevant and minor particles?
The Third Report quantified the health risk from particles and attributed a definition to each of three activity ranges, based upon the direct health effect that might be expected. These ranges are denoted by the terms minor, relevant and significant and are based on the particle's Caesium-137 (137Cs) activity content.
For all particle activity ranges, the health effect is based on the particle remaining stationary against the skin for a number of hours for the effect to occur. This information is more fully defined in Section 3 of the DPAG’s Third Report, section 5.7.
Significant: 137Cs activity greater than 106Bq (1,000,000Bq)
Significant particles are likely to cause serious ulceration (visible after 1-2 weeks). This may take several weeks to heal along with the associated risk of infection which might require medical treatment.
Relevant: 137Cs activity between 105 and 106Bq (100,000 and 1,000,000Bq).
Relevant particles would require a minimum of seven hours stationary contact to have any discernible effect. Time periods of 1-2 days would be required for any reddening with small lesion of the skin to be observed. The affected area of skin would be expected to heal completely within 2-4 weeks without further problems. DPAG considers that anyone coming into contact with the type of particles so far found on Sandside beach is unlikely to experience any observable effects.
Minor: 137Cs activity less than 105Bq (100,000Bq)
Minor particles will not cause discernible health effects. Included in the consideration of the definition of minor particles is also the very low probability of contact with such a particle on Sandside beach. Equally, the effects caused by ingestion and inhalation are also reproduced in the Third DPAG Report.
Where are the particles now?
Particles released through the liquid effluent pipeline mixed with sand and were deposited on the seabed. Larger, more active particles seem to have remained close to the discharge point with smaller, less active particles, being transported to the east and west. Fragments of particles may have dissolved or been transported to the east of the Pentland Firth. Particles of this size have not been found and would not be an environment or health concern.
Where have particles been found?
Particles have been detected and removed from the Dounreay foreshore and Sandside beach, with single finds (minor) at Dunnet and Murkle beach.
The first recorded particle was found and recovered during routine monitoring of the Dounreay foreshore in 1983. The foreshore is immediately north of the Dounreay site and although not within the nuclear licensed site boundary, the area is not easily accessible by the public.
In 1984, during monitoring of neighbouring beaches a particle was found and recovered from Sandside beach, a privately owned beach 2.5km west of Dounreay.
In 1984, a further 26 particles were retrieved from the foreshore.
In 1997 UKAEA, with contractor support, developed hand-held underwater survey equipment and initiated a preliminary seabed survey off the Dounreay foreshore by divers. It was during these trials that the first offshore particles were identified and recovered.
[ A retired health physics surveyors has informed the site that he detected a particle of higher radioactivity at Sandside in 1984. Although extensive searches were carried out the site has been unable to locate official records to verify this.]
How many particles have been found?
Regularly updated tables showing how many particles have been found are published on this website.
Over 1400 particles have been identified and removed to date – those detected on the beaches have been removed along with those detected on the seabed by divers. Particles on the seabed have also been detected by remotely operated vehicles but these machines did not have a retrieval capability until December 2007 and therefore some particles were detected but not recovered from the offshore environment.
What happens when you find a particle?
If a particle is found on the beach, SEPA is informed. Early readings from the monitoring vehicle provide a quick estimate of the activity. Once recovered the particle is brought back to the Dounreay site and taken to a laboratory.
Once the site laboratory takes receipt of the particle it is measured for its radioactive content prior to storage in a secure store. All work with a particle, its movement and storage are subject to rigorous procedures which are compliant with UK regulations. Once all scientific work has been completed, the particles will be encapsulated for disposal as solid intermediate level waste.
What safeguards have been put in place to ensure that the present work of decommissioning Dounreay cannot lead to further disturbance and release of radioactive particles into the environment?
A new low level liquid waste treatment system was installed in 1990. This system provides improved particulate settlement and includes a final filtration stage. Other facilities, known to contain particles, are being isolated from the environment as part of the decommissioning process.
It is highly unlikely that there is a continuing release of particles from the site today. Work is in hand to isolate the shaft from the environment and to consider how to seal the old diffuser chamber to ensure that these potential routes can be completely ruled out. Areas where large numbers of particles are concentrated such as waste facilities will be emptied and the waste conditioned for placement in engineered containment.
Are particles still being released from the site today?
It is highly unlikely that particles are escaping from the site today. Filters were fitted to individual plants in 1984/85 to prevent further releases, a new low-level liquid effluent system installed and additional filtration put in place.
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Is the shaft the source of particles?
Although the shaft was used for disposal of particles, research has shown it is highly unlikely that the shaft is the source of particles. We know that approximately six tonnes of MTR reprocessing swarf was sent to the shaft for disposal in the 1960s. To reach the sea, the swarf would need to be carried by groundwater along fissures in the rock and emerge on the seabed. A major project is underway to isolate the shaft from the environment and retrieve its contents.
Is the old discharge system a likely source of particles?
Particles could have lodged in the old discharge system which includes a diffusion chamber which sits 25 m below the seabed, 600m offshore in water 23m deep. The risers from this chamber were plugged in 1999, but it is known that this did not isolate the system. This system has not been used routinely since 1992 when a new set of discharge pipes and discharge manifold were installed.
There is a potential for particles to reside in the old discharge system and a project is underway to consider how best to deal with the old diffuser. At present water flows are so low this is unlikely to be a continuing source.
What are you doing about the old diffusion chamber?
Divers have examined the rock around the chamber and tried to gain access down the risers.
A camera was lowered down one of the risers to approximately 23m below the seabed where a second lead plug obstructed progress. Radiation dosimeters were attached to the camera and also on the cable 10m from the camera. Information on the radioactivity on the seabed and around natural fissures, close to the diffuser, was also obtained.
Further investigation is planned and information gathered will assist in considering the options for remediation.
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 will be 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.
Why has monitoring the seabed for particles been limited mainly to a zone lying between Strathy Point and Brims Ness, with the seaward boundary between 0.5 and 1.5 km offshore? Should other areas to the east and west of this zone and possibly in deeper water be surveyed for particles as well?
Surveying has concentrated in areas where it is believed particles reside. In the years when divers were used to survey the seabed, they concentrated in areas where they were finding particles and where a computer model predicted there could be particles. They were subject to restrictions on water depth but did carry out seafloor monitoring more remote from Dounreay, such as Brims Ness and Strathy.
With the development of a remotely operated vehicle (ROV) system in 2005, it was possible to survey in deeper areas and in bays to the east and west of Dounreay. The results of the ROV surveys in 2006 were consistent with a more limited spread of particles than a computer model predicted. Monitoring off Thurso, Strathy and Dunnet Bay has taken place and no particles have been detected.
In 2007 further monitoring supported an emerging picture of a limited spread of high activity particles (significant), a wider but more diffuse spread of lower-activity particles (relevant and/or minor) north-eastwards, with a population of lower-activity particles moving west into Sandside bay. Further surveys in a limited area at the headland at Brims Ness did not find particles, which had been predicted by a computer model, but were consistent with surveys conducted in 2006.
Beyond the 30 metre water depth there may be particles but these are either very small, well dispersed or deeply buried in sediment which will be largely undisturbed because of the calmer dynamics of the seabed in deeper water.
Is there a fishing ban in place?
Yes. As a precaution, the removal of fish, crustacea and molluscs is prohibited in an area of 2km (1.2 mile) radius centred on the disused Dounreay discharge point near where the highest population density of particles has been detected.
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Why is the FEPA zone for the control of fishing and the collection of seafood limited to a 2km radius centred on the offshore location of the old liquid effluent diffuser since this zone does not include all areas where particles have been found?
The exclusion zone was established using a Food and Environment Protection Act (FEPA) Order put in place by the then Scottish Office in October 1997 as a precaution after divers started to find particles near the old diffuser outfall (widely acknowledged as the most likely release point).
The FEPA zone has been within the Food Standard Agency’s remit since its inception in April 2000. Although some particles have been found in more recent years outside the 2km radius, these have tended to be at the lower end of the activity range. A large amount of fish, crustaceans and mollusc sampling is undertaken on an annual basis and to date no particles have been found in any of these samples.
The FSA will continue to assess the food chain risk based on updated information received from SEPA, though to date the FSA has not deemed it necessary to amend the FEPA zone on the basis of food safety.
Are new particles continuing to arrive at Sandside beach or is it possible that they have been on the beach for sometime and you are only just finding them?
The accumulated knowledge on the offshore and beach particles has been reviewed and the seabed off Dounreay is now believed to be the source of the particles which are detected on local beaches. The particles are generally moved eastwards, but some also move west into Sandside Bay. It is known that the height of the beach at Sandside changes regularly, just like any other beach of this type, so at any time there may be a mix of recently arrived particles and particles which have been present for some time within the beach. DPAG have reviewed the change in beach height with the available detection equipment and used this information to produce recommendations on monitoring frequency and detection capability in their third report.
The beaches are monitored and any particles detected are recovered. During recovery the activity of each particle is estimated, together with the depth of the particle on the beach, the location and height of the beach. It is essential to monitor the beach consistently over a prolonged time period to allow a better understanding of the arrival rate of particles on to the beach. Current studies are providing information on whether recently detected particles might be new arrivals or older arrivals revealed by beach erosion. The DPAG Fourth Report, due to be published in September 2008, will cover this topic in detail.
If new particles should continue to reach the beaches in the future from offshore, what is the annual frequency at which such arrivals could be expected?
The consistent monitoring of the beaches allows the arrival/detection rates to be studied. It is important to look at trends over many months as detection rates may be influenced by many factors. The rate of arrivals is also dependent on a combination of offshore conditions and the direction of sediment movement.
Should bay shallows and the beach areas wetted by the tides also be monitored for particles so that new arrivals may be detected and removed at the earliest opportunity and, if so, with what frequency?
There has been a focus on improving the monitored area of beaches and this has led to an increase in the monthly monitoring footprint of Sandside to include areas only briefly uncovered by the low tide. The monitoring performance is continually assessed to identify improvements in particle detection. Monitoring of sandy sediments just off Sandside beach was undertaken in 2007. Further assessment of the monitored area will be included in the DPAG 4th report.
What is the possibility of particles of whatever size being blown inland or being washed into the dune systems at Dunnet and Sandside beaches during storm conditions and what arrangements are in place or planned for monitoring above the intertidal level?
Routine monitoring of the beach at Sandside includes a substantial area of sand above the high tide mark. In addition, the sand dunes at Sandside were monitored in 2000 and no particles were found. Extensive monitoring of the golf course took place in 2007. Again, no particles were detected.
At Dunnet, areas above the high tide mark have also been monitored in 2005, 2006 and 2007.
No particles have been found in these surveyed areas, at Sandside or Dunnet. It is not impossible for particles of the same size as fine sand grains to be blown into the dunes or washed in by storms, but should this happen the particles would be expected to be of a low activity.
How dangerous are particles?
It depends on their size. As a rule of thumb, the smallest particles, in size and activity (minor) are the least hazardous and the largest ones the most hazardous (significant).
Where are the larger particles?
Significant particles have been found on the seabed near Dounreay and on the Dounreay foreshore where access by the public is limited. All particles found on the Dounreay foreshore have been removed and over 900 particles have been recovered from the seabed by divers.
What are the risks from particles?
A number of studies on the potential effects of particles have been completed by independent bodies. Explanations of the hazards and risks can be found at:
Scottish Environment Protection Agency particles research
Committee on Medical Aspects of Radiation in the Environment (COMARE)
Dounreay Particles Advisory Group (DPAG)
Are there any health and safety risks for workers to consider when clearing debris deposited by storms from the beaches and from associated access areas?
The health and safety of workers is equally as important and is considered for all particle monitoring operations. In addition to radioactivity, there is also a general hygiene risk associated with picking up debris but with appropriate precautions any risk to health is extremely small. Risk assessments are carried out before any work starts.
Are small particles, which may not be detected by current survey equipment, of concern for health, particularly if suspended in the air by the action of the wind?
Particles of this size would be likely to be low in activity (minor particles) and would therefore be unlikely to pose any discernible effect on health.
What would happen to me if I swallowed a particle?
In the unlikely event of swallowing a lower activity particle (minor or relevant) and if the particle remained stationary against the gut wall for 6 hours ulceration may be caused which would be repaired naturally. A particle in the significant category would induce more serious radiation effects. DPAG’s Third report covers this subject in more detail.
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Could a particle become lodged for long enough in a sensitive part of the body, such as the eye or the ear, or in a fold of the skin, or in a wound, or in the gut if ingested, so that adverse health effects could be caused?
Some of the particles found on Sandside beach are sufficiently radioactive to be of health concern if they were inhaled, ingested or trapped close to the skin. However, independent experts have calculated that the risk of contact with such a particle is so low, such that currently any restriction of access or of activities is not warranted. When visiting any beach simple hygiene measures should be applied, including washing hands after handling any materials or objects.
Particles, of the activity found on local beaches, would need to be in direct, static contact with the skin for at least seven hours to cause any observable effect, such as reddening of the skin.
DPAG’s Third Report covers this subject in more detail.
Are the beaches safe to use?
DPAG considered the work carried out by the Health Protection Agency and concluded that only significant particles post a realistic potential hazard to members of the public.
To date particles found on publicly accessible beaches have been in the minor and relevant category and there is an extremely small possibility of a member of the public coming into contact with a particle. If they did so, no adverse health effects would be expected.
The beaches continue to be open to the public and a programme of monitoring regulated by the Scottish Environment Protection Agency (SEPA) reduces the risk further through the detection and removal of particles. It also provides re-assurance that significant particles are not present at these beaches.
Is it safe for children to play on the beaches, to build sandcastles and to paddle in the sea?
Monitoring of beaches continues to find occasional particles of radioactive material. Some of the particles, found on Sandside beach, are sufficiently radioactive to be of health concern if they were inhaled, ingested or trapped close to the skin. However, independent experts have calculated that the risk of contact with such a particle is so low, such that currently any restriction of access or of activities is not warranted. When visiting any beach simple hygiene measures should be applied, including washing hands after handling any materials or objects.
Is it safe to hold family picnics on the beaches?
The beaches are regularly monitored for radioactive particles. If there was a realistic chance of a serious health risk from the presence of particles on the beaches access to the affected beaches would be restricted by the relevant authorities. When visiting any beach simple safety measures should be applied, including washing hands after handling any materials or objects, purely for hygiene purposes.
Is it safe to walk dogs along the beaches?
The beaches are regularly monitored. If there was a health issue access to the affected beaches would be restricted by the relevant authorities.
What is being done about this pollution?
Monitoring of beaches: Subject to access, monitoring is carried out on the Dounreay foreshore and public beaches at Sandside, Thurso, Scrabster, Crosskirk, Brims Ness, Melvich and Dunnet.
The site has a requirement under the Radioactive Substances Act discharge authorisation to monitor the beaches to criteria set by SEPA. In addition, other monitoring has been carried out including surveying at Dunnet beach in 2006 and 2007, Peedie Sands and Murkle beach.
Larger beaches require more monitoring effort as tides and the amount of daylight available need to be taken into account before the vehicle is deployed. To put this into perspective:
Monitoring of Dunnet beach, with a total area of about 1,000,000 square metres of sand, to a depth of 10cm is equivalent to 12,500 average-sized dump-truck loads or approximately 50 average-sized shipping carriers of sand.
Working with contractors, Nuvia, the system has been continually developed over the years to improve its performance.
In 2006, the Government's Committee on Medical Aspects of Radiation in the Environment concluded that the effectiveness of past and present systems used to monitor beaches demonstrated the capability of detecting larger particles to at least a 20cm depth.
In 2007, evaluation of the upgraded beach monitoring vehicle was carried out on Dunnet beach and COMARE and DPAG confirmed the significant improvement in the detection capability of the upgraded system which exceeds the operational requirements set by SEPA.
The full report can be found on COMARE's website and in DPAG's Third report.
Monitoring the seabed: A programme of radiological surveys of the seabed has been carried out. Historically these surveys were carried out by divers.
A research programme led to the development of a remotely operated vehicle – which has the advantages of operating in deeper water (>25m), covering the seabed faster than divers and removing the need for diving activities and their associated risks. The remotely operated vehicle used to survey the seabed during 2005 to 2007 did not have the capability of retrieving particles but the knowledge which was accumulated has allowed independent experts to assess the potential numbers of particles remaining in this area.
Forward programme: Following an extensive review of the available information, tests and trials, independent reports and stakeholder feedback the Dounreay site has now developed a management strategy to target and recover particles from the areas where significant and relevant particles have been found on the seabed and to continue to recover particles from the beaches. The removal of most of the higher activity particles (significant/relevant) from the seabed is likely to considerably reduce the number of particles arriving on-shore.
What are the typical specific activities of the radioactive particles found to date in the marine and coastal environment at Dounreay?
The range of particle specific activities, based on caesium-137 analysis measured so far is 1.43E07 to 1.85E10 Bq/g,
Particles are normally characterised on their caesium-137 content. The more ‘active’ particles on the seabed and foreshore tend typically to be of the order of 1.0E6 MBq (1 MBq) to 1.0E8 Bq (100 MBq), whereas particles located and recovered from Sandside beach are, to date of much lower activity, less than 5.0E5 Bq (0.5 MBq)).
To whom is the site accountable?
The activities at Dounreay are scrutinised by a number of important stakeholder organisations
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