Natural analogue studies: present status and performance assessment implications

• Published in: Journal of contaminant hydrology 1997-04, Vol.26 (1), p.3-17
• Main Authors: Smellie, John A.T., Karlsson, Fred, Alexander, W.Russell
• Format: Article
• Language: English
• Subjects: In situ experiments; Natural analogues; Natural systems; Public awareness; Safety performance assessment
• ISSN: 0169-7722; 1873-6009
• DOI: 10.1016/S0169-7722(96)00053-8

Studies of natural geological and archaeological systems as analogues to long-term processes, which are predicted to occur within a radioactive waste repository environment, have become increasingly popular over the last 10 years or so, to the extent that such studies form an integral part of many national programmes for radioactive waste disposal. There is now a common consensus that the natural analogue approach is a very useful scientific methodology to: (a) identify and understand processes and mechanisms analogous to those which could occur in the vicinity of a repository over realistic timescales, (b) derive input data which have been successfully used to test some of the laboratory-based models which form the basis of long-term repository performance assessment, and (c) to produce data which can be input directly to performance assessment models. Increasingly, analogues are playing an important role in public awareness, enabling the layman to understand better the concept of radioactive disposal and demonstrating the reliability of the disposal system over long periods of geological time. The complexity of geological systems means that it is very often difficult and sometimes impossible to quantify precisely the physico-chemical boundary conditions necessary to model a particular geochemical process or mechanism. Consequently, the availability of quantitative analogue data is limited when repository performance assessments are considered. However, this in no way detracts from their value in building confidence by demonstrating that important processes do exist and by showing qualitatively that they behave in a way predicted by models based on laboratory-derived data. The transfer of natural analogue data from the complexity of field studies to simplistic models which, by necessity, are used in performance assessments, is an area of activity which is presently being addressed. Field analogue studies are now being planned to interface with laboratory experiments and, ultimately, with in situ field experiments. This is a promising avenue of research which should provide a more quantitative use of natural analogue data in testing and further developing models used in (or supporting) repository performance assessments.