Further recommendations on the work to identify the source and possible health effects of the radioactive particles found in the environment around the UKAEA site at Dounreay

COMARE published recommendations for further work to be undertaken around the Dounreay site in it's sixth report in 1999. The further recommendations given below were formulated following a visit by the Dounreay Working Group to the UKAEA site at Dounreay in October 2001.

Background

COMARE were asked by the Secretary of State for Scotland to consider and advise on the incidence of leukaemia and related issues around the Dounreay Nuclear establishment in 1986. COMARE published it's original advice and recommendations on the possible increased risk of leukaemia in young people near the Dounreay site in it's Second report in 1988. As part of the continuing investigation by COMARE, documentation was provided by Her Majesty's Industrial Pollution Inspectorate (HMIPI) on the occurrence of radioactive particles on the Dounreay foreshore and the public beach at Sandside Bay. The UKAEA informed COMARE that the particles were the result of an accidental spillage in 1965. A Working Group was appointed by COMARE to investigate this issue. The Working Group visited the Dounreay site in 1994 where other potential sources of particulate contamination were identified. These sources included the Intermediate Level Waste Shaft which is located close to the Dounreay foreshore on the edge of the UKAEA site. A joint report on the potential health effects and possible sources of the particles was published with the Radioactive Waste Management Advisory Committee (RWMAC) in 1995. Further investigations by the Group following publication of the joint report resulted in the publication, in 1999, of COMARE's Sixth Report that reconsidered the health implications and possible source of the particles.

Current information

Monitoring of the beaches from Melvich to Thurso has been undertaken by UKAEA. Currently the monitoring is concentrated in seven areas, Melvich, Sandside, Dounreay foreshore, Cross Kirk, Brimms Nest, Scrabster and Thurso. To date, particles have only been found in two areas: the Dounreay foreshore and the beach at Sandside Bay. Particles have also been found in the off-shore areas out from the Dounreay foreshore and Sandside Bay. The off-shore particles have been identified using both diver and towed instrument surveys. Divers have also been used to survey water uprisings from the seafloor in the areas off the Dounreay foreshore.

The particles found, both offshore and on the foreshore at Dounreay and the beach at neighbouring Sandside Bay are fragments from either the Dounreay Fast Reactor (DFR) or the Materials Testing Reactor (MTR) each of which have their own characteristics. These particles result from milling operations that were undertaken on the fuel prior to reprocessing during the 1960s. Investigations by UKAEA have shown that the MTR particles are fairly robust whereas the DFR particles are more fragile. The particles are variable in size and activity concentration.

UKAEA advised COMARE in October 2001 that the numbers of particles found to date would indicate that there was a reservoir in the offshore sediments, however, UKAEA agreed that there was a need to eliminate other possible sources.

There are currently three main areas under consideration as the possible source or sources of the particles. These are the inactive site drains, the discharge pipe and diffuser, and the ILW shaft.

Inactive drains

A spillage of radioactive material was accidentally washed into the inactive drains in 1965. Since that time investigations by UKAEA initially confirmed that the drains were clear of particles, however, more recent investigations have identified a blocked drainage pipe that contained a small number of radioactive particles. These particles were however quite different in character to those found off-shore.

Low Level Liquid Discharge system

Liquid discharges from the Dounreay site were previously routed to the sea via a discharge pipe that ran though a tunnel and culminated in a diffuser with 16 uprisers, 20 m in height, that discharged into the sea. Although the diffuser was sealed it has not been ruled out as a possible source of the particles and UKAEA continue to investigate the seabed in this vicinity. A new effluent discharge system was installed in 1992; there is no suggestion that particles are being released into the marine environment from this source. Decommissioning of both the current and old diffuser is planned as part of the Dounreay Site Restoration Plan.

The Intermediate Level Waste shaft

The shaft was constructed to provide access to the adit that joins the main effluent tunnel and a concrete plug was used to seal the shaft from the adit when construction was complete. The shaft is currently capped following an explosion in 1977. Prior to this it was commissioned for the disposal of various wastes, including MTR fuel element components and swarf from the milling operations over the period from 1959. Currently investigations are being undertaken by UKAEA to establish methods of isolating this shaft ready for removal of the waste and decommissioning. As part of this work water movement in the shaft and surrounding rock strata is being studied. At the last visit to the site by COMARE all parties agreed that the shaft should not be eliminated as the source of the particles unless a very strong case is made.

Recommendations

Monitoring

1. COMARE reiterates the recommendations given in paragraphs 5.3 and 5.4 of it's Sixth report on the need for regular and comprehensive monitoring of beaches in the area of the Dounreay site and recognises and welcomes the improvements undertaken by UKAEA. The improvements have mainly been achieved by the introduction of a motorised vehicle with a GPS system for more effective monitoring of the beaches. However, further improvements could be made to the current monitoring strategy and equipment to ensure that the majority of the relevant particles are being found. Consideration should also be given by UKAEA to the statement by Scottish Ministers that 'SEPA ensures that there is sufficient monitoring in place to ensure that particles finding their way to the beach at Sandside Bay are promptly detected and removed'. However, it is COMARE's view that the removal of particles could be limited to those that might affect the health of individuals that come into contact with them. COMARE is also aware that the probability of an individual coming into contact with a particle is very small.
2. COMARE recommends that improvements are made in the frequency, coverage and detection limits currently employed and that these improvements should be guided by the results of the latest research being undertaken on behalf of SEPA on the health effects of the particles. The aim should be for a programme that detects particles that, should a member of the public come into contact with them, might be harmful to their health. It is also recommended that improvements to the beach monitoring involve extending the existing methods rather than a fundamental change in the methodology. This will enable consistent comparisons to be made with earlier monitoring data. Information from the GPS system should also be used to ensure maximum coverage of the areas to be monitored.
3. Improved instrument sensitivity would either enable particles having activities of around the current detection limit to be detected at greater depth, or give greater flexibility in the required speed of the vehicle, thereby improving the coverage of the areas monitored. Currently to achieve the detection limits set by SEPA the vehicle needs to travel at a maximum speed of 0.8 m sec^-1. As the speed is controlled manually, this requires constant vigilance from the driver of the vehicle. An alternative could be an automatically controlled vehicle that would not have this limitation. Improved instrument sensitivity could also result in the detection of lower activity particles. However, COMARE recognises that this may not be required when the results of the latest studies on the health effects of the particles are considered. In addition, the weight of the current vehicle makes monitoring of the upper deep sand areas and the wet sand shoreline very difficult; a lighter vehicle may not have these problems.
4. It is recommended that the beach monitoring programme should be further reviewed. Consideration should be given to the proximity to the site, the likelihood of particles being discovered and also the occupancy of the particular beach by members of the public. It is COMARE's view that the rocky areas to the western end of the beach at Sandside Bay should be included in the monitoring programme as the collection of sand in these areas suggests that particles could also be found there. There is also a need for monitoring to give public reassurance, and so COMARE recommends that monitoring should continue on the more frequently used beaches, for example, the beach
5. During the visit to Sandside Bay in early October 2001 COMARE noted its disappointment with the public notices displayed, which were supposed to give information regarding the radioactive particles and their possible health implications. Two different notices had been provided, one by the owner of the beach and one by UKAEA. These notices were judged to be very confusing for the general public, as they gave different interpretations of the current status of the beach, one notice being overlaid on the other. COMARE believes that this results from the poor communications between the two parties supplying information. This situation should be remedied as soon as possible. COMARE recommends that the current notices be replaced with something giving a full and consistent message, and preferably one that is agreed with all concerned parties.

Off-shore particles

6. COMARE welcomes the continuing work undertaken by UKAEA to identify the extent and source of the off-shore particles and in particular the progress made with the oceanographic modelling, the offshore particle surveys, the repopulation studies and the identification of freshwater upwellings from the sea floor. However, COMARE recognises that further work is needed to identify the source or sources of the off-shore particles. It is important to identify whether the particles result from a single or multiple historical discharge, are being continually fed from a particular source or cache or are the result of a combination of these. COMARE accepts that all of the particles are the result of historic discharges from the 1960s but feels that the latest data does not support the hypothesis that the particles are already fully dispersed to the environment. COMARE's view is that one or more caches of these particles probably exist and that these result in a continuing feed of particles to the environment.This would explain the persisting plume of particles observed off the site and the occurrence of particles in rocky areas of the Dounreay foreshore where sand is largely absent.
7. COMARE strongly recommends that the surveys to identify the freshwater upwellings should be continued. It is also recommended that the results from the off-shore studies should be considered together with the information obtained from the investigations that are being undertaken on the Intermediate Level Waste disposal shaft. Studies in both of these areas should be linked to give a co-ordinated approach to the experimental design. This would give better data on the movement of groundwater and aid in the confirmation or exclusion of the ILW shaft as the continuing particle source.
8. COMARE welcomes the proposed extension of the repopulation studies to cover the area of the old diffuser. It is COMARE's view that the results from these experiments should confirm or eliminate the diffuser and the upstands as a source of particles to the off-shore environment. COMARE recognises that the old diffuser is to be decommissioned towards the end of the programme given in the Dounreay Site Restoration Plan. If the diffuser is found to be a source of particles COMARE recommends that this is isolated and removed as soon as is practicable.

Intermediate Level Waste shaft

9. The Intermediate Level Waste shaft has been considered as part of COMARE's remit as this may be a source of the particles if a possible pathway exists via the movement of freshwater to the off-shore environment.
10. COMARE is concerned that the Shaft Isolation project continues to be totally independent of the Particle Investigation project. COMARE reiterates the recommendation given above that important data could be obtained by the co-ordination of these two projects. It is COMARE's view that the present hydrogeological investigations are taking insufficient account of the need to identify the possible movement of particles from the shaft into the geological strata. For the ILW shaft to be eliminated as a source of particles this pathway needs to be investigated fully.

Overall

11. COMARE notes the effort expended by UKAEA on the problem of the particles and the progress made. COMARE welcomes the fact that its previous concerns that destructive testing of particles were prevented by regulatory control have been relaxed to some extent. Nevertheless it recognises the difficulties faced by UKAEA in that comprehensive measurements on all of the recovered particles cannot be undertaken. Understanding the source(s) of the particles is nevertheless an important factor in achieving the UKAEA's aim to identify the Best Practicable Environmental Option (BPEO) for the Dounreay site.

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