Coupled Analyses of Steam Line Break for Integral PWR

This study investigates NuScale small modular reactor (SMR) during a steam line break scenario. The scenario is simulated with the thermal hydraulic system code and the neutronics code. The development of the coupling between the codes is done in this work. The main goal is to perform safety analysis, providing corresponding data for code validation, and study the feasibility of the coupling.

The computational tools which are used to perform the numerical calculations are part of VTT’s modular calculation system Kraken. Kraken uses modules, which in this study are the nodal neutronics code Ants and the thermal hydraulic system code TRACE. This study is part of the McSAFER project funded by the Euratom research and training programme.

The coupling between TRACE and Ants was achieved, and the steam line break event was simulated successfully demonstrating the feasibility and advantages of Kraken. This work also includes the development of coupling the computational fluid dynamics program OpenFOAM with Kraken and simulating stationary state. However, this part is not in the scope of this report.

The NuScale SMR behavior complied with the limitations set by the acceptance criteria, but additional studies with other computational tools and experimental facilities are needed to validate the results. Oscillatory behaviour was found in the secondary circuit warranting further research on the novel helical-coil steam generators the NuScale design incorporates.