Uncertainty and sensitivity methods in support of PSA level 2

Dealing with uncertainties in PSA level 2 requires using a set of statistical techniques to assess input uncertainty, to propagate uncertainties in an efficient way, to characterize appropriately output uncertainty and to get information from computer code runs through an intelligent use of sensitivity analysis techniques. The purpose of this paper is to give an overview of statistical and probabilistic methods and tools to answer to these topics, and to provide some guidance about their suitability and limitations to be used in a PSA level 2. Our position about their implementation in L2 PSA software has been written; it could be noticed that a lot of these methods are very time-consuming, and seem more suitable for the analysis of submodels or for focusing on specific questions. (authors)