Sensitivity and uncertainty analysis of atmosphere stratification modelling in MISTRA using lumped-parameter code COCOSYS

The paper presents simulations of one of the containment atmosphere mixing experiments - MISTRA M5 (formation of stratified conditions by a jet/plume steam release and vertical thermal gradient) - performed using a lumped-parameter code COCOSYS. Special nodalisation features required to compensate for the method limitations are described and used. Additionally, an uncertainty and sensitivity analysis of the simulation is presented. The parameters with large uncertainties having high influence on the results are identified. The importance of an adequate nodalisation to account for the occurring processes, e.g., in this case, plume/jet releases, is showed.