Analysis of Boron Dilution sequence in a NuScale Power Module using TRACE

Within the framework of the “High-Performance Advanced Methods and Experimental Investigations for the Safety Evaluation of Generic Small Modular Reactors” (MCSAFER) H2020 European project, the Universidad Politécnica de Madrid (UPM) research group is developing, among other tasks, a TRACE-1D model of a NuScale Power Module (NPM) to simulate the Boron Dilution and the Steam Line Break transients. Particularly, the simulation of a Boron Dilution transient in a NPM accounting for the impact of the reactivity feedbacks on the core power has been carried out and the results are presented in this work. To do so, it was necessary to implement a high-order numerical method in the model to avoid numerical diffusion. The results shows that an important increase in the core power is produced due to the injection of unborated water within the primary coolant system and, consequently, the pressure in the primary side is also increased. For that reason, the reactor is tripped by the Reactor Protection System, and the Decay Heat Removal System actuation is also demanded to achieve a proper core-cooling during the whole transient.