Boron dilution sequence analysis in NuScale SMR usingTRACE

In this study, the analysis of the Boron Dilution sequence is performed by means of the TRACE-1D model of the NuScale Reactor Coolant System (RCS) developed by UPM within the Work Package 4 of the McSAFER project frame in order to compute the time to loss the shutdown margin. The data presented in the Design Certification Application (DCA) report of NuScale available at the NRC website along with with other original references from NuScale have been used to build the commented TRACE model in which only the primary side is considered and the secondary side is implemented as a boundary condition. In this study, the power is constant, so no reactivity feedbacks are considered in order to compute the Boron concentration evolution with time. To do so, one of the high-order numerical technique available in TRACE is applied to solve the spatial differences and a semi-implicit method is used for the time integration. Finally, the results obtained using the TRACE-1D model are presented and a good agreement is shown with the ones presented in the DCA report.