[en] The results of a study on the potential radiological consequencies of the geological disposal of vitrified high level waste which have recently been published (Preliminary Assessment of the Radiological Protection Aspects of Disposal of High Level Waste in Geologic Formations. Hill M.D. and Grimwood P.D. NRPB-R69 1978 (H.M.S.O.)) are discussed. The four main barriers which can prevent the return, or influence the rate of return, of radioactivity to man's environment from a waste repository are considered. The radionuclides which the study suggests would give rise to the highest doses and the predicted peak individual doses which would arise from these nuclides are quoted. The study indicates areas in which major uncertainties exist including; prediction of geological events which might lead to a failure of geological containment; events and processes due to the presence of the repository itself which could lead to loss of its integrity; the behaviour of vitrified waste under expected disposal conditions; and rates of migration of radionuclides with ground-water. The results of the preliminary study suggest that there is no reason to rule out geological disposal, but there is considerable work to be carried out before a decision can be taken on the acceptability of this disposal option. (U.K.)

[en] Two of the options for disposal of highly active wastes from high water reactors in quantities that would be generated by postulated nuclear power programs by the year 2000 are discussed. They are, disposal in the ocean bed and disposal into geological formations on land. Using simple models, assessments were made of possible transfer of radioactivity to man. The studies mainly identified the areas of work needing further research. Calculated doses were useful as an indication of the order of magnitude of both individual and collected doses which might arises from such disposals. (U.K.)

[en] British Nuclear Fuels operates the the United Kingdom national solid low-level radioactive waste disposal site at Drigg, Cumbria. Historically, disposals have been into clay-based trenches. In 1988, however, the first concrete vault disposals commenced. The principal features of the completed trenches and the vault are described, including the associated drainage systems and the use of an 'engineered' clay in areas beneath the vault. In optimising disposals in terms of costs and environmental impact, a range of future waste forms and vault designs have been developed. These are summarised. Particular attention has been given to their long-term performance in terms of environmental protection and radiological impact. Some results of a comparative performance assessment are presented. These considerations have led to high-force compaction and grouting of wastes as the principal conditioning method to be adopted, together with a relatively simple concrete vault and a low permeability, clay-lined cap

[en] A preliminary assessment, recently carried out by the National Radiological Protection Board, of the radiological consequences of the disposal of highly radioactive wastes on the ocean floor is considered. This assessment was concerned chiefly with developing a model describing how radioactive material deposited on the floor of the deep ocean could eventually lead to the irradiation of man, especially through food chains. It was assumed that the waste from the power programme will be incorporated into a glass material to form a solidified product and that this solidified waste will be stored for 10 years following reprocessing. Vitrifying processes for waste are described. The main routes for return of radioactivity to man considered are; consumption of near-surface fish, consumption of deep-sea fish, consumption of food derived from plankton, exposure to contaminated coastal sediments, and inhalation of resuspended activity from coastal sediments. It was found that the dominant route of individual and collective exposure for all nuclides was from consuming food derived from marine plankton. It is felt that there are many uncertainties to be resolved before the disposal of high-level radioactive waste on the ocean floor is acceptable. (U.K.)

[en] Low level radioactive wastes have been disposed of at the Drigg near-surface disposal site for over 30 years. These are carried out under a disposal authorization granted by the UK Environment Agency. This is augmented by a three tier comprehensive system of waste controls developed by BNFL involving wasteform specification, consignor and waste stream qualification and waste consignment verification. Until 1988 wastes were disposed of into trench facilities. However, based on a series of integrated optioneering studies, new arrangements have since been brought into operation. Central to these is a wasteform specification based principally on high force compaction of wastes, grouting within 20 m³ steel overpack containers to essentially eliminate associated voidage and subsequent disposal in concrete lined vaults. These arrangements ensure efficient utilisation of the Drigg site capacity and a cost-effective disposal concept which meets both national and international standards. (author). 7 figs

[en] Short communication

[en] The paper is based upon presentations and discussions at an NEA workshop. Fundamental issues related to human intrusion assessments are reviewed. Experiences with scenario development, probability estimates, consequence calculations and regulatory criteria are highlighted. Examples are given of mitigation measures to lower the probability and/or consequences of human intrusion. Work on the assessment of human intrusion has developed significantly in the last decade and assessments of human intrusion are now seen as forming an integral part of overall safety studies for repositories. Clear presentation of the fundamental underlying assumptions and the results of assessments is an important factor. Simple, robust steps and models are likely to be more credible and too much sophistication likely to be counter productive. 6 refs., 1 fig., 1 tab