Simulation of the boron dilution sequence in NuScale SMR using 1D and 3D modeling approaches in TRACE

The objective of this work is the analysis and comparison of the results of the NuScale boron dilution sequence simulated by means of  1D and 3D modeling approaches performed with TRACE code. Additionally, to assess the Helically Coiled Steam Generators (HCSGs) behavior under asymmetrical conditions, a  ±10 % of variation from the nominal values of the feedwater mass flow in the respective feedwater lines has been implemented in the TRACE models. By doing so, it has been demonstrated that the NuScale HCSGs performance is able to make asymmetrical effect disappear almost completely in the RCS and that NuScale is able to deal with this kind of accidental sequences with a large safety margin. Finally, it is worth noticing that although similar results have been obtained using the 1D and 3D modeling approaches, the application of the 3D approach is highly desirable in order to be sure that the physics involved in the problem is captured by the simulations of the accidental sequences. These analyses have been performed within the framework of the “High Performance Advance Methods and Experimental Investigations for the Safety Evaluation of Generic Small Modular Reactors” (McSAFER) H2020 European project.