CROSS-COMPARISON OF DIFFERENT TECHNIQUES FOR SENSITIVITY ANALYSIS IN SEVERE ACCIDENTS: APPLICATION TO A SBO IN A PWR

Along the “Management and Uncertainty of Severe Accidents” (MUSA) project, attention has been paid to the unfolding of Uncertainty Analysis (UA) when dealing with Severe Accident (SA) scenarios. While the quantification of the uncertainty linked to SA simulations' results is the focus, a complementary sensitivity analysis is highly recommended to identify the variables being the root of it. Following this path, the present paper reports the application of different sensitivity methods to an unmitigated Station Black Out (SBO) in a Pressurized Water Reactor (PWR). The variables with the highest impact on the simulation outcomes according to the different methods are reported and a discussion is made concerning the sensitivity process optimization. Results show that the different techniques agree on identifying the initial inventory of Iodine in the gap as the parameters with the highest influence on the calculated amount of Iodine released to the environment. The analysis highlighted also the need to support the application of sensitivity methods with expert judgment to corroborate the physical consistency of the obtained results.