Uncertainty and sensitivity study for WWER-440/V-213 containment

WWER-440/V-213 containments are characterised by a so called Bubble Condenser that is a pressure suppression system. We have applied 73 zone nodalization for LB LOCA (Large Break Loss of Coolant Accident) analysis with COCOSYS V2.4. We have prepared a list of COCOSYS code uncertain input parameters and their state of knowledge. We have generated the selected set of COCOSYS results required by SUSA (Software for Uncertainty and Sensitivity Analysis). The uncertainty analysis shows that with statistical two-sided (95%, 95%) tolerance limits the maximum pressure in break zone, calculated with COCOSYS, falls in the range of 1.96 - 2.13 bar. According to the sensitivity analysis results, 6 out of 60 uncertain input parameters (among them initial temperature and humidity of the zone atmosphere, cross section areas of junctions) have significant influence on the maximum pressure