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RWMAC's Review of: Radioactive Particles at UKAEA Dounreay
Press Release:
30 March 1999
The Radioactive Waste Management Advisory Committee (RWMAC) today publishes the advice it has given to the Secretary of State for Scotland on the issue of the radioactive particles found near the United Kingdom Atomic Energy Authority's (UKAEA's) nuclear site at Dounreay, in Caithness, Scotland.
In January 1999, the Committee published its broad based review of radioactive waste management issues at Dounreay. However, this made only brief reference to the radioactive metallic particles, some 380 in all, which have been retrieved from areas both on and off the site, including the offshore sediments, over the past 20 years.
The new report sets out the RWMAC's views on the work undertaken by UKAEA to locate, retrieve and analyse these particles. It evaluates the implications of this work for identifying the origin of the particles and how they may have been released to the environment, the areas where hidden "caches" of particles might still exist, and the mechanisms by which they could represent a potential source of radiation exposure of the public. It also considers the direction that future work should take in order to understand and control the possible risk to the public from exposure to the particles.
The RWMAC acknowledges that in recent years, UKAEA has conducted a programme of investigation into the particles problem which is comprehensive in scope and professional in approach. To date, however, it has not been possible to identify definitively the source, or sources, of the particles.
The RWMAC's main conclusions concerning the source, or sources, of the particles are as follows:
- the particles come from historic operations at Dounreay; there are no ongoing activities that could lead to their generation;
- neither the site itself nor the Dounreay Foreshore* are likely to contain a hidden cache of particles;
- there are certainly particles in the sea bed sediments offshore from Dounreay. It is too early to say how many particles are there, or how they are distributed within the sediments, but initial estimates suggest that the total number of particles could be substantial;
- the most likely overall scenario is that particles are being carried onto the foreshore from a cache, or caches, formed within the sediments some years ago; it is also possible that the sediments are currently being "drip-fed" with particles from another source, or sources. There are two possible candidates for this "drip-feeding" source. The first is the diffusion chamber", located below the sea bed at the end of the liquid waste discharge pipeline, which was almost certainly used, on at least one or two occasions until the late 1960s, for the discharge to sea of particle-contaminated effluent arising from the treatment of spent fuel prior to reprocessing. The second, less likely, source, is the Intermediate Level Waste Disposal Shaft, where large numbers of particles were routinely disposed of, under authorisation, over a number of years up to 1968;
- the RWMAC recommends that studies of the diffuser need to be undertaken urgently to determine whether or not there is an ongoing release process and, if so, whether it can be terminated, either by recovering or sealing the diffuser. The possibility that the Shaft is a source needs further work and reinforces the RWMAC's recommendation, already made to Government, that UKAEA should take early action to remove all the waste in the Shaft.
The report makes clear that the ultimate aim of work on the particle problem must be to protect the health of the public. It follows that any remedial work, undertaken once the source, or sources, of the particles have been established, must be consistent with this aim. It must also be proportionate to the risks to the public. Proposals for the investigation of the distribution of particles in the offshore sediments, and any attempt to remove them, would not, therefore, be acceptable if they increased these risks by disturbing the sediments and possibly causing the redistribution, or even uncontrolled release, of the particles. If removal proves not to be feasible, the measures taken for public protection need to be commensurate with the very low likelihood of a member of the public actually encountering a particle.
In order to understand the particle problem better, and therefore assess the degree of risk to the public, the RWMAC believes that UKAEA should ensure that it is able to track the rate and location of future particle finds in as effective a manner as possible. The report points to the need for further development work by UKAEA to improve its "Groundhog" particle detection system which, the Committee believes, is not commensurate with the requirements of beach monitoring. The Committee recommends that there should be greater emphasis on monitoring public beaches in the vicinity of Dounreay, in addition to Sandside beach**.
An assessment of the potential health risks posed by the particles is given in a complementary report by the Committee on Medical Aspects of Radiation in the Environment (COMARE), published simultaneously with this report.
* Dounreay Foreshore is the strip of land, partly of rock and partly sand and gravel, running east-west in front of the Dounreay site, flanked by the Dounreay cliffs and by the sea. 177 particles have been found on the foreshore (which is closed to the public) at a rate of just under 11 a year.
** Sandside beach is at Reay, three kilometres from the site, and is open to the public. Three particles have been found there; one in 1984 and two in 1997.
Notes to Editors
The independent Radioactive Waste Management Advisory Committee was set up in response to a recommendation of the Royal Commission on Environmental Pollution's Sixth Report on Nuclear Power and the Environment. Its terms of reference are:
"To advise the Secretary of State for the Environment, Transport and the Regions, and the Secretaries of State for Scotland and for Wales on the technical and environmental implications of major issues concerning the development and implementation of an overall policy for all aspects of the management of civil radioactive waste, including research and development; and on any such matters referred to it by the Secretaries of State."
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