Euradwaste '08 - EU Bookshop - Europa

Sensitivity Analysis Techniques for the Performance Assessment of a RadioactiveWaste
Repository
Ricardo Bolado Lavín 1 , Klaus-Jürgen Röhlig 2 , Dirk-Alexander Becker 3
1 Institute for Energy, European Commission DG-JRC, Petten, The Netherlands
2 Technical University of Clausthal, Germany
3 GRS-Braunschweig, Germany
Summary�
Sensitivity Analysis (SA) is a key element in the Performance Assessment (PA) of a Radioactive
High Level Waste (HLW) Repository. It helps gaining information about the system, understanding
the relation between input parameters and output variables and steering new experimental
and theoretical research to increase the degree of knowledge about the system. The
Integrated Project (IP) PAMINA is devoting a large effort to the research in this area and the
dissemination of results among its partners. Among the activities under development are a review
of SA methods, a benchmark of SA techniques and the application of different SA techniques
to a PA results coming from several national programs. After the end of this activity,
PAMINA partners will get a better understanding of the rationale behind every available technique
and about their capabilities and shortcomings.
1. Introduction
SA methods may be divided into three broad types: Local methods, screening methods and global
methods. Local methods focus on the study of the system model behaviour under very specific system
conditions (the vicinity of an input space point), while screening methods focus on the functional
relation between inputs and outputs disregarding input parameter distributions, and global
methods focus on how the whole input space (taking into account input distributions) maps into the
output space. Though all of them are important and provide relevant information about the system
model, screening methods and global methods fit better within the structure of a PA, and that is the
reason to focus all efforts on them.
Three main activities are being developed in this area: the review of SA methods available in the
scientific literature, the development of a benchmark on SA techniques and the practical application
of SA techniques to results of PA studies produced by different partners. The objective of the review
of SA techniques is to provide a snapshot of most useful SA techniques and to provide guidance
about merits and shortcomings of each one. Screening techniques are useful to identify irrelevant
input parameters that can be set to their nominal value not losing information. Global methods
may be classified as Monte Carlo based methods, variance based methods, and graphical methods.
The SA benchmark has been designed as a two-step process. The first step is dedicated to analyse a
set of mathematical functions most of whose sensitivity indices are well known. The targets in this
step are to debug SA computational tools used, to get skills in their use and to get progressively in
contact with specific features of mathematical models such as (lack of) linearity, (lack of) monot-
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