Euradwaste '08 - EU Bookshop - Europa

PAMINA – The Treatment of Uncertainty in PA and the Safety Case
Summary
Daniel Galson and Roger Wilmot
Galson Sciences Ltd, Oakham, UK
The European Commission’s PAMINA Project (Performance Assessment Methodologies in
Application to Guide the Development of the Safety Case) has the aim of developing a common
understanding of and improving integrated PA methodologies for the geological disposal
of radioactive wastes. A core component consists of research on methods for the treatment of
uncertainty in PA and the safety case
This paper summarises the overall programme of work on treatment of uncertainty, and the
results of an initial international review of the treatment of uncertainty and a recently completed
task on the regulatory evaluation of uncertainty. A workshop aimed at discussing the
approaches used by regulators in evaluating uncertainties in the safety case was organised by
the Swedish regulators and Galson Sciences Ltd in June 2008. The workshop provided a forum
for discussion of how regulators can assess and compare quantitative and qualitative lines
of reasoning and evidence in safety cases that are subject to uncertainties.
1. Background
Development of a safety case for the management of long-lived radioactive waste involves consideration
of the evolution of the waste and engineered barrier systems, and the interactions between
these and relatively complex, natural systems, such as climate change. The timescales that must be
considered are much longer than the timescales that can be studied in the laboratory or during site
characterisation. These, and other factors, give rise to various types of uncertainty e.g., on scenarios,
models, and parameter values used in modelling, which need to be taken into account when assessing
long-term performance of a geological disposal facility. It is important to follow a clear
strategy for dealing with uncertainties when developing a safety case.
The European Commission’s PAMINA Project (Performance Assessment Methodologies in Application
to Guide the Development of the Safety Case), which has 27 partner organisations and runs
from 2006 to 2009, has the aim of improving and developing a common understanding of integrated
performance assessment methodologies for disposal concepts for spent fuel and other long-lived
radioactive wastes in a range of geological environments. Galson Sciences Ltd is responsible for the
co-ordination and integration of the Research and Technology Development Component “RTDC-2”
of the PAMINA Project.
The objective of RTDC-2 is to allow development of a common understanding of different approaches
to the treatment of uncertainty in PA, and to provide guidance on, and examples of, good
practice on how to treat different types of uncertainty in the context of the development of a postclosure
safety case, both as a whole and in specific areas. Guidance on the development of work in
RTDC-2 has come from an initial review of key drivers and methodologies for the treatment of un-
377