COMARE Statement on the radioactive particles found in the local coastal environment resulting from operations at the Dounreay facility

1. COMARE is aware that detailed assessments of the movement and potential hazard from radioactive particles found at Sandside Bay will only be possible when consistent monitoring data are available over a timescale of several years. COMARE therefore recommends that regular and consistent monitoring of Sandside Beach (including beach profiling as appropriate) be undertaken without restriction in the future and for an absolute minimum period of at least two years.

2. There has been an increase in the number of particles finds, particularly in early 2003. COMARE is of the opinion that this increased rate could result from a combination of up to three possible causes, namely (i) the lack of monitoring prior to this date due to restrictions set by the landowner; (ii) the enhanced seasonal degradation of the beach profile; (iii) the improved monitoring system employed. The range of activities among the finds made in early 2003 is consistent with the previous group of recoveries from Sandside beach, but the 2003 group has a lower mean activity and a greater proportion of particles with activities in the lower half of the pre-2003 range. This pattern is consistent with what would be expected from improved monitoring. The increased rate of finds in March-April 2003 might be due to any combination of factors (i) - (iii). An extended period of monitoring using consistent methods is now required before it can be determined whether (a) the new monitoring equipment is detecting (in greater numbers than before) a fairly constant supply of particles to the beach, or (b) all or part of the March-April finds are particles that had been stored in the beach sands for some time previously and are now being detected.

3. COMARE recommended in its statement on the Dounreay particles made in May 2002 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.'

COMARE notes the improvements made in the monitoring systems currently in use. However, COMARE is disappointed that the recommendation made that the monitoring data provided by the new Groundhog system be consistent with that produced previously was not followed. In this regard, COMARE would expect that any new monitoring system would be trialled in parallel with the existing system for a period of at least six months in order to permit comparability to be established.

4. COMARE endorses the need for practical experiments using the new Groundhog Mark II technology to characterise the performance of this monitoring vehicle. Comparative experiments should also be made using the original Groundhog Mark I technology or a duplicate of this system if the original is no longer available.

5. COMARE is still concerned that there is insufficient evidence available to exclude the land to sea pathway via the movement of water through the rock strata. In order that any such pathways can be identified, COMARE reiterates its recommendation given in May 2002 regarding offshore freshwater upwellings.

'COMARE strongly recommends that the surveys to identify the freshwater upwellings should be continued.'
The surveys should aim to determine conclusively whether upwellings exist and if found their locations and extent. The results are required before this pathway can be excluded.

The methods employed should be those most appropriate for the task of searching the seabed for point phenomena such as radioactive particles or freshwater springs. Since 1997, divers using hand-held instruments have proved much more effective in searching for particles than towed instruments. COMARE recommends that divers be employed in the search for upwellings and springs. Furthermore, COMARE asks UKAEA to take note of the possibility that freshwater upwellings may be tidal in their function, and that searches should be made at the part of the tidal cycle most likely to yield positive results.

6. COMARE regrets the delay in the SEPA funded projects to investigate gut transport and the possibility of dissolution of these radioactive particulates. These data are essential to refine further the estimates of the health effects of the particles that could be encountered by members of the public.

7. Limited information available regarding the composition of some of the individual particles recovered suggests that a source could be test material from the Materials Testing Reactor (MTR). COMARE recommends that investigations are made to ascertain the route of disposal of the materials tested in the MTR and the information provided for consideration.

8. COMARE welcomes SEPA's decision to facilitate analysis of the particles. COMARE would encourage SEPA to ensure further classification and characterisation of the particles so that a complete definitive database of information on each of the particles is produced; COMARE is concerned that the current database may contain inaccurate information.

9. COMARE encourages UKAEA to establish a formal Standard Operating. Procedure to be followed when a particle is found, to include recovery procedures, measurement and analysis procedures and the definition of a standard data set.

10. Based upon currently available evidence, the radiation dose to an individual consequent upon ingestion of a typical particle from Sandside Bay is estimated to be roughly equivalent to the average UK annual background radiation dose of 2 mSv. This is less than the previous estimate, due to better knowledge of the composition of the particles and improved modelling of the radiation dose to the lower large intestine (Darley, Charles, Fell and Harrison 2003). COMARE believes that the probability of a member of the public encountering a particle remains extremely small. The outcome of the studies mentioned in paragraph 6 above will permit a more definitive opinion on health effects associated with the particles.

Reference

Darley PJ, Charles MW, Fell TP and Harrison JD (2003). Doses and risks from the ingestion of Dounreay fuel fragments. Radiat Prot Dosim, 105, 49-54.

28 June 2004