Euradwaste '08 - EU Bookshop - Europa

There are at least three non-numerical or qualitative methods for dealing with uncertainties in PA
and the safety case:
1. Robust design, where uncertainties are managed by using conservative engineering design
principles. An example of this approach is provided by the Finnish and Swedish programmes,
where the engineered barriers used in the KBS-3 concept are extremely robust, making some
uncertainties associated with the far field and biosphere easier to discount.
2. Qualitative assessment methods: programmes in many countries employ qualitative assessment
methods, and in some situations they are considered to be as important as the quantitative
methods. This is particularly true where an assessment considers events far removed in space
and time from the original emplacement of waste in the disposal facility, and there are very
large uncertainties associated with the quantitative assessments.
3. Quality Assurance (QA) for development of the PA and safety case: implementing appropriate
QA systems for all aspects of disposal facility development programmes plays a part in the
process of building a compelling safety case and obtaining approval from regulators and stakeholders.
Many programmes have applied custom-designed or internationally accredited QA procedures
to their operations.
3 . PAMINA RTDC-2
3.1 WP2.1 Methodological Research for Treatment of Uncertainty
WP2.1 consists of four tasks:
2.1.A Regulatory Compliance. A workshop was held in June 2008 that examined the treatment of
uncertainty in PA and the safety case with respect to regulatory compliance. The outcome of
this workshop is discussed in Section 4.
2.1.B Communication of Uncertainty. This research aims to understand the effectiveness of different
methods for communicating disposal system performance, communicating how it has
been determined, and communicating the uncertainty associated with the determination and
its significance. The results of a workshop designed to test different approaches to communicate
to lay stakeholders are available [2].
2.1.C Approaches to System PA. This research is examining the advantages and disadvantages of
different approaches to the quantification of uncertainties in system-wide PA calculations,
including deterministic scenario-based assessments versus probabilistic assessments, levels
of conservatism and realism in PA, exploration of the potential of hybrid stochasticsubjective
uncertainty treatment, and alternative approaches for presentation of results from
safety analysis / uncertainty analysis in the form of graphical outputs.
2.1.D Techniques for Sensitivity and Uncertainty Analysis. This research aims to compare the
advantages and disadvantages of different methods for applying sensitivity analysis to PA
calculations. The research comprises a review of the use of sensitivity analysis in PA,
evaluation of the use of sensitivity analysis techniques for a range of actual radioactive
waste disposal facility concepts, testing of sensitivity analysis techniques based on use of
complex and simplified generic PA models, and an international benchmark study aimed at
testing a wide range of the sensitivity analysis techniques on two test cases.
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