Analysis of epistemic and aleatory uncertainties in the context of a dynamic fire-PSA

In the frame of the nuclear research project RS 1112 "Development of Methods for an Advanced Probabilistic Safety Analysis, Particularly Level 2" funded by the German Federal Ministry of Economics and Technology (BMWi), a probabilistic dynamics analysis was performed for an exemplary scenario of a cable fire inside the containment of a reference Konvoi-type nuclear power plant Besides the fire dynamics simulated by a deterministic model, the analysis took into account the stochastic (aleatory) uncertainties in fire detection and fire fighting as well as the interaction between the dynamics and the stochastic uncertainties. At the end, it was possible to determine, for instance, the (conditional) probability for the hot gas layer temperature to exceed a specified value for more than x seconds. The results of the probabilistic dynamics analysis were subjected to an epistemic uncertainty and sensitivity analysis. The uncertainty analysis investigated how well a calculated (conditional) probability could be determined due to the fact that numerous epistemic uncertainties (in parameter values, model formulations, etc.) were involved in its calculation. The sensitivity analysis provided a ranking of the identified epistemic uncertainties with respect to their contribution to the uncertainty of the probabilities.