Decision analysis has been with us for at least half a century. Over that time it has developed from a theoretical paradigm for individual rational choice to a practical tool for individuals, small groups and 'unitary' organisations, which helps them towards a sound decision-making mindful of the behavioural characteristics of individuals and group dynamics. Decision analysis has also shown its worth in the context of stakeholder engagement and public participation. The time is right for it to be more widely used in making societal decisions. However, to achieve that we need to realise that in many circumstances it will only be one input to the political process that leads to the actual decision. Recognising that suggests that our community of decision analysts needs to deconstruct our paradigm and attend more to communicating the result of the analysis in comparison with other inputs to the societal decision.

The objective of the CONFIDENCE project has been to identify, assess and communicate the uncertainties that arise in managing and recovering from a nuclear accident. To do that, it is important to be clear on what uncertainty means, how it arises and how we might analyse it. In fact, there are many forms of uncertainty, some of which we can assess with current tools, but some of which are more nebulous and difficult to deal with. Nonetheless, all need to be communicated to the emergency managers. Starting with a review of different categories of uncertainties, and using examples from the CONFIDENCE project, this paper discusses how the various uncertainties are manifested in nuclear emergency management. It concludes with a simple framework for categorising and analysing them. The overall intention is that such a framework could contribute to a broader discussion on identifying and handling uncertainties with nuclear emergency management actors

One of the strengths of decision analysis is that it can deal with most uncertainties; but, alas, not all. Sometimes uncertainties are too deep: that is, within the time and data currently available, no agreement is possible between decision makers, experts, and stakeholders on their quantification as probabilities. The possible range of probabilities may be so great that any sensitivity study would show that virtually all actions may be optimal. Recently, such cases have been approached by scenario-focused decision analyses in which the deep uncertainties are fixed at several “interesting” values. These approaches are showing considerable potential, but there is a problem. The assumptions on which decision analysis is based do not necessarily apply, because scenarios are not quite “small worlds” in Savage’s sense. This paper discusses the difficulty, offers a way forward, and demonstrates some of the points within an example on nuclear energy strategy.