The potential use of natural analogue studies in radioactive waste disposal: a review

Radioactive waste must be disposed of in such a way that it remains safe for periods of time which are often well beyond our ability to guarantee control and surveillance. The performance of the repository cannot, of course, be demonstrated practically nor by experiment because of the long time scales involved. Model predictions should be valid for thousands of years and, in the case of very long-lived radionuclides, even hundreds of thousands of years. Consequently, safety analysts over the past 10 years have recognised that the study of natural systems (or natural analogues) provides opportunities to test, by observation and measurement, many of the geochemical processes that are expected to influence the predicted reliability of radioactive waste containment over realistically long periods of geological time. In addition to the time scale factor, these analogue studies attempt to understand the multiprocess complexity of the natural system by an interdisciplinary approach, which contrasts with the limitations of the laboratory. This paper reviews the application of natural analogue studies to demonstrate the safety of deep radioactive waste disposal; emphasis has been put on the Swedish disposal concept as an example. Examples of such applications are described and finally the main performance assessment objectives are discussed. Future areas of improvement are also addressed. (authors). 69 refs., 4 figs., 1 tab