USE AND QUALIFICATION OF THE UMAE UNCERTAINTY METHODOLOGY HAVING AS BASIS THE CATHARE2 CODE

The present paper deals with the use of the UMAE (Uncertainty Methodology Based on Accuracy Extrapolation). This methodology allows the calculation of uncertainty in the prediction by thermal-hydraulic system codes of transient scenarios relevant to Nuclear Power Plants. The UMAE has been applied in an international exercise promoted by OECD/CSNI (OECD Committee on the Safety of Nuclear Installations), called UMS (Uncertainty Method Study); the qualification of uncertainty methodology constitutes one of the main purposes of UMS. The methodology has been applied in the proposed study having as the basis both the Relap5/mod2 and the Cathare2 codes calculations. In this paper, the results obtained by the use of Cathare2 code are discussed. One small break Loss of Coolant Experiment performed in the Japanese LSTF (Large Scale Test Facility) has been taken as reference test in relation to which code uncertainties have been predicted. The results of the application proved the capabilities of UMAE in predicting uncertainties at least in the considered scenario.