22 Jul 2021

UMAN – Towards a common understanding of uncertainty management in radioactive waste management


EURAD, the European Joint Programme on Radioactive Waste Management, constitutes a step change in European collaboration towards safe radioactive waste management. The programme supports EU Member States in the implementation of the Waste Directive taking into account the various stages of advancement of national programmes and serves to foster mutual understanding and trust between Joint Programme participants. The Council Directive 2011/70/EURATOM requires that transparency be provided by ensuring effective public information and opportunities for all stakeholders concerned to participate in the decision-making process. Programmes for the disposal of radioactive wastes are implemented in a series of phases, in which the scientific understanding of the disposal system, the design of the disposal facility and its safety case are progressively advanced. Such an approach allows the implementation of a stepwise decision-making process whereby decisions relating to the development, operation and closure of the facility are made in the presence of both irreducible and reducible uncertainties. It also enables a gradual management of these uncertainties and of those which may emerge during the implementation of the programme. Hence, the management of uncertainties and associated stakeholder involvement represent key parts of a successful programme planning as well as key issues when developing or reviewing the safety case of disposal facilities.

The main objectives of the Uncertainty Management multi-Actor Network (UMAN) are to provide an opportunity to different actors of EU Member States to share their experience and views on uncertainty management and to identify emerging needs that could be addressed by future EURAD activities. It brings together 34 organisations from 16 Member States and Associated Countries ensuring a well-balanced representation of the different types of actors involved in the programme (i.e. Waste Management Organisations, Technical Support Organisations, Research Entities and Civil Society organisations). UMAN includes the review of existing uncertainty management strategies, approaches and tools (Figure 1).

Figure 1: Generic uncertainty management strategies and options – High-level picture © NAGRA / Bel V
Figure 1: Generic uncertainty management strategies and options – High-level picture © NAGRA / Bel V

Furthermore, existing knowledge and views on the identification, classification, characterisation and significance of uncertainties associated with specific topics are synthesized. A particular focus is put on the following topics: waste inventory and impact of predisposal steps, site and geosphere, human aspects, spent fuel and the near-field of geological disposal facilities. Then, possible options to manage these uncertainties are identified and discussed. Interactions between different types of actors including Civil Society and the understanding of their views are central to UMAN. This is achieved notably through a series of workshops and seminars. They are aimed at meeting the shared objective of fostering a mutual understanding of uncertainty management strategies, approaches and preferences.

The seminars provide opportunities to perform pluralistic analyses of key outcomes of different UMAN tasks. The first seminar, which was held in October 2020, set the scene for this process by addressing the meaning of uncertainty management for different actors and of its relationships to risk, safety and the safety case. It gathered 49 participants representing the views of the actors involved in EURAD as well as of regulatory authorities. Keynotes presenting the views of each type of actors on four key topics (Meaning of Uncertainty Management, Types of Uncertainty, Possible Evolutions of Uncertainty and Interactions with Civil Society) served as a basis for pluralistic discussions in working groups. Many noteworthy issues were raised during this seminar. For instance, the exchanges highlighted the fact that safety-relevant uncertainties extend well beyond scientific and technical “known unknowns”. It is indeed often considered that technical uncertainties can be adequately addressed, but non-technical uncertainties associated with the programme itself (uncertainties in governance, transparency, available resources, etc.) which matter to Civil Society are also important (Figure 2).

Figure 2: Clusters of uncertainties associated with the different phases of a radioactive waste disposal programme identified as important by Civil Society organisations.  © MUTADIS / NTW
Figure 2: Clusters of uncertainties associated with the different phases of a radioactive waste disposal programme identified as important by Civil Society organisations.  © MUTADIS / NTW

Furthermore, a particular attention should be paid to “unknown/ignored knowns” (i.e. available knowledge one may not be aware of or fail to consider in one’s activities) and “unknown unknowns” (i.e. what one does not know one does not know). Preliminary analysis of the results also indicates that there may not be so many differences between the actors’ views at a general level (agreement on the importance of uncertainty management in the safety case) but differences may appear in the concrete implementation according to cultural contexts, the programme phase, the role of the actors in the process and their respective risk appetite. The outcome of these interactions allows establishing a more global picture of uncertainty management complementing and enriching the results of UMAN.

The Management Board of UMAN is composed of the following persons:

Frank Lemy, Bel V, Brussels, Belgium
Valéry Detilleux, Bel V, Brussels, Belgium
Dirk-Alexander Becker, GRS, Braunschweig, Germany
Daniela Diaconu, RATEN, Pitesti, Romania
Astrid Göbel, BGE, Peine, Germany
Agnieszka Strusińska-Correia, BGE, Peine, Germany
Julien Dewoghélaëre, MUTADIS, Paris, France



Frank Lemy
Bel V