Evaluation of a Double-Ended Guillotine Break Transient in a Three-Loop PWR-900 like with TRACE Code Coupled with DAKOTA Uncertainty Analysis

In the present study, the model of a reference generic three-loop PWR-900 like western type reactor has been developed and a double-ended guillotine break on the cold leg has been simulated by the TRACE code. Through the SNAP graphical interface, a DAKOTA uncertainty analysis, based on the probabilistic method to propagate input uncertainty, has been performed by selecting uncertain parameters related to the safety injection system and to the initial plant status. In particular, six uncertain input parameters have been considered: the accumulators’ initial pressure and temperature, the safety injection system temperature and flow rate, the reactor initial power and the containment initial pressure. The main figure of merit selected for the application of regression correlation is the hot rod cladding temperature. Both Pearson and Spearman’s correlation coefficients have been computed for the cladding temperature of the hot rod to characterize its correlation with the input parameters in the different phases of the transient. In addition, the dispersion of the calculated data have been evaluated for selected relevant thermal- hydraulic parameters, such as the primary pressure, the core mass flow rate and the water level in the vessel.