Quantification of the uncertainties of the physical models of CATHARE 2

The goal of this paper is to draw up a balance sheet of the use of the CIRCE tool, by CEA (France) for the CATHARE 2 code. CIRCE is a statistical tool which is aimed at estimating the uncertainties of the physical models of CATHARE 2 and which can replace the expert judgment generally used. The determination of these uncertainties, with CIRCE or expert judgment, makes up an essential first step for the majority of methods in uncertainty analysis. In the first part of the paper, the CIRCE tool is rapidly described and attention is focused on a hypothesis of linearity made by CIRCE. A work program using CIRCE for the determination of the uncertainties of some physical models of CATHARE 2 has been defined and achieved, the studies of which are listed. Due to the hypothesis of linearity and also because CIRCE is a quite new statistical tool, some precautions must be taken when using it. They are precisely described in the second part of this paper and illustrated in an example. (author)