International Atomic Energy Agency Group 3 Moderator: Jack Rapporteur: Joerg

International Atomic Energy Agency Subjects to tackle Uncertainty and uncertainty management Make a link, place a hook towards uncertainty (management) Understanding of the safety envelope. Clarification of difference between design target and safety envelope. Involvement of regulator in both aspects? Regulatory requirements and safety envelope Verbalize concept of agreement between operator and regulator

International Atomic Energy Agency Subjects to tackle Term “initial state”  clarify, confusion on evolution of initial state - discuss. ‘Initial conditions’ Closure activities included to define initial state Get rid of “assumed initial state” Uncertainty on initial state due to transients

International Atomic Energy Agency

Helpful PRISM Outcomes of Task Group 4: Managing Uncertainties conducted by Roger Seitz were included into the PRISM report (chapter 9).

International Atomic Energy Agency Task 4: Managing Uncertainties Summary Roger Seitz 05 December 2012

International Atomic Energy Agency Rough Graphic for Types of Uncertainty

International Atomic Energy AgencyConclusions The need to address the performance of natural and engineered systems and policy/governmental status over long time-scales inevitably leads to complex uncertainties that pose challenges to decision-makers. Awareness is the first step towards managing uncertainties. Five general classes of uncertainties were identified: data/parameter, model, future/scenario, resources and contextual. The first three categories are site specific, quantifiable to differing degrees, and can be considered within a safety assessment. These uncertainties have to be considered in the design target/safety envelope. The last two are difficult to quantify and are more relevant at the Member State level and need to be considered when developing waste management policies and as part of project planning. These uncertainties can cause modifications/changes during the operation period.

International Atomic Energy AgencyOptions Confidence Building Use of Management Systems (LOOP) Involvement of Interested parties Discussion of Options Passive Safety (Safety Envelope) Defence in Depth Robustness (Safety Envelope) Scientific and Technical / Engineering Principles (Design Target) Understanding the Disposal System Monitoring (Design Target) Independent Peer Review Completeness of the Safety Case (update due to loop result) Traceability and Transparency Complementary Safety Indicators Multiple Lines of Reasoning Plans for Addressing Significant Unresolved Issues (Plan and implementation as relevant to Design Target/ Safety Envelope) Use of International Standards Managing Uncertainties Sensitivity Analysis Uncertainty Analysis Quality assurance/Quality control Communication of confidence building Site Characterization Expert judgment/elicitation Verification/Validation of Models Plume matching/assimilation Decision analysis (multi criteria and multi attribute, cost benefit) Waste acceptance criteria Laboratory experiments Reality check – simple calculation Demonstration analogues Alternative conceptual models Data estimation – inverse methods Alternative designs Balancing realism and conservativism Monitoring and surveillance Use of different types of models (probabilistic/deterministic) Safety Functions and FEPs Concept of reasonable assurance Documentation of assumptions (regulatory and resources)

International Atomic Energy Agency Subjects to tackle Term “initial state”  clarify, confusion on evolution of initial state - discuss. ‘Initial conditions’ Closure activities included to define initial state Get rid of “assumed initial state” Uncertainty on initial state due to transients

International Atomic Energy Agency

Not Helpful - Necessary Modifications Title Instead of preclosure safety please use operational safety Page 1, Capter It is not only the nuclear industry, which produces waste (MIR) Thousands of years may be the wrong order for long term safety Page 2, Chapter civil engineering works is not the challenge but mining activities Page 5 and 6 Handshake is misleading, propose to remove this term Example on page 6/7 number of possible defective packages undetected should be included into the Design Target This example is not a good one. Example on page 6 instead of “determines” influences or is an indicator delete “sorption” General: Terminology should be checked!!!

International Atomic Energy Agency