The impact of retrievability on disposal of radioactive waste

There are discussions in various countries about whether and to what degree the ability to retrieve wastes might be built into geological repositories for long lived radioactive waste. It is generally accepted that repositories should be designed so that retrieval will never be necessary on safety grounds. Nevertheless, reasons for retrieval have been put forward. The ways in which retrievability might be built into geological repositories and various expected impacts of such actions are briefly discussed in this paper. A preliminary comparison of some notional geological disposal strategies with varying degrees of retrievability is proposed. The comparison is qualitative because at present there are few detailed designs for geological repositories with retrievability and few assessments of the safety and other aspects of such repositories. The comparison has the aims of highlighting those factors that differ most from one strategy to another and identifying which of these factors require further assessment in order to make more complete and quantitative comparisons. The framework used for the preliminary comparison is that of a multi-attribute analysis, such as might be employed in an environmental impact assessment (EIA). This type of framework is chosen because it would be used in many countries to aid decisions between disposal options or strategies. The framework encompasses radiological and nuclear safety factors but goes well beyond these and includes a number of factors that are not quantifiable in the technical sense. However, consideration of such factors is considered important because they can have a significant impact on decision-making. The groups of factors are: radiological, nuclear safety and financial (quantifiable factors); non-radiological environmental impacts (partially quantifiable factors); non-quantifiable attributes (such as ethical and societal factors). (author)