WASTE DISPOSAL
4. CONFIDENCE AND CONFIDENCE BUILDING
4.4. Confidence versus uncertainty in the context of decision making
Uncertainty will exist in any human endeavour. Decision making has always to take uncertainty into account. The real issue for decision making is that of confidence. Decision making is hardly ever based only on numerical values for uncertainty:
2 Just as in some languages where ‘uncertain’ and ‘unsafe’ are translated with the same word even if they are different concepts.
PESCATORE
— Even if probabilistic assessments of the safety of nuclear power plants have been in use for many years, no nuclear power plant has ever been licensed on the result of only a probabilistic number.
— Confidence does require a demonstration that uncertainties have been dealt with, and there are means to deal with scientific uncertainty, i.e.
those techniques typically applied in data analysis and model testing.
However, when it comes to long term predictions, there are special issues to deal with.
— A mixture of quantitative and qualitative arguments will have to be provided to engender confidence both in the provider and the reviewer.
On the one hand, confidence can be seen as the complementary concept to uncertainty, just as risk is complementary to safety. On the other hand, building confidence requires more than just uncertainty analysis; it is about communicating quality and demonstrating inclusiveness at the same time.
4.5. Conclusions
Confidence and confidence building are important technical and managerial concepts to achieve and define the quality of a modern safety case.
Confidence building is a management tool for preparing and reviewing a modern safety case. A set of criteria has been developed to help in building confidence, i.e. in achieving, evaluating and communicating confidence. One distinctive feature of the safety case is the provision of a confidence statement in order to enable dialogue and provide improved support to the decision at hand.
5. OVERALL CONCLUSIONS
Confidence and confidence building are technical and managerial concepts of high relevance in connection with the preparation and review of modern, long term safety cases for disposal. They arose from the technical debates held in the 1990s around the issue of validation, and entered the waste management vocabulary for technical and managerial reasons rather than for purposes of addressing the concerns of the public and society at large.
Uncertainty will exist in any human endeavour. Decision making has always to take uncertainty into account. The real issue for decision making is that of confidence. Decision making requires only (a) confidence to support the decision at hand, and (b) a strategy, in which there is confidence, to deal at later stages with any uncertainties that have the potential to compromise safety.
SESSION IIc
Importantly, confidence has decision making value only once it is shared.
Therefore, aiming for confidence implies, at the same time, a policy of trans-parency and openness to all the actors involved in decision making.
On the one hand, confidence can be seen as the complementary concept to uncertainty, just as risk is complementary to safety. On the other hand, confidence requires more than just uncertainty analysis: it is about communi-cating quality and demonstrating inclusiveness at the same time.
Confidence is not the same as trust, and confidence building implies explaining the means by which confidence was acquired. This explanation presupposes clarity of purpose and discipline. There exist proven methods that help in building confidence, i.e. in achieving, evaluating and communicating confidence.
REFERENCES
[1] OECD/NUCLEAR ENERGY AGENCY, “Validation: an overview of Defini-tion”, in GEOVAL’94 — Validation through Model Testing, OECD, Paris (1995).
[2] OECD/NUCLEAR ENERGY AGENCY, Geological Disposal of Radioactive Waste — Review of Developments in the last Decade, OECD, Paris (1999).
[3] OECD/NUCLEAR ENERGY AGENCY, Confidence in the Long-Term Safety of Deep Geological Repositories — Its development and communication, OECD, Paris (1999).
[4] OECD/NUCLEAR ENERGY AGENCY, Lessons Learnt from Ten Performance Assessment Studies, OECD, Paris (1997).
[5] OECD/NUCLEAR ENERGY AGENCY, International Peer Reviews in the Field of Radioactive Waste, Questionnaire on principles and good practice for safety cases, OECD, Paris (2005).
[6] OECD/NUCLEAR ENERGY AGENCY, Safety of Disposal of Spent Fuel, HLW and Long-lived ILW in Switzerland, An international peer review of the post-closure radiological safety assessment for disposal in the Opalinus Clay of the Zürcher Weiland, OECD, Paris (2001).
[7] INTERNATIONAL ATOMIC ENERGY AGENCY, Geological Disposal of Radioactive Waste, IAEA Safety Standards Series No. WS-R-4, IAEA, Vienna (2006).
[8] OECD/NUCLEAR ENERGY AGENCY, Post-closure safety case for geological repositories: Nature and purpose, OECD, Paris (2004).
PESCATORE
DISCUSSION
T. TANIGUCHI (IAEA): At the beginning of your presentation, you defined ‘disposal’ as the waste management end point providing safety and security, and you juxtaposed safety and security and gave the impression that they have comparable weight.
Is it your view that such security includes security against malicious acts?
Also, how is security linked to the safety case?
C. PESCATORE (OECD/NEA): That definition of ‘disposal’ indicates that putting things away in a geological repository also helps to avoid malicious intrusion. It will provide protection against security breaches.
Modern safety cases do not talk much about security. In fact, I do not think that security is directly mentioned in safety cases by itself — only together with safeguards.
T. TANIGUCHI (IAEA): I was wondering what the approach to this issue should be in the future.
C. PESCATORE (OECD/NEA): When giving definitions, it is important to understand what they mean. To me, the first one — from the Joint Convention — is not a very effective definition when we are talking about long term problems.