Comprehensive Simulation of the Integral Molten Salt Reactor (IMSR) Using a Lumped 3D Modeling Approach

Abstract

Terrestrial Energy leads the development of the Integral Molten Salt Reactor (IMSR), where power is produced from fission in the liquid fuel salt flowing through a graphite core. Employing the system- level simulation code, Flownex Simulation Environment, Terrestrial Energy comprehensively models the entire IMSR system. Within this system level code, the graphite core sections are modeled using a sophisticated lumped 3D approach, with downstream components like the Primary Heat Exchanger (PHX) explicitly incorporated to simulate heat transfer. The code is also augmented with embedded neutronics, enabling this model precise simulation of both steady-state and transient behaviour, accounting for temperature changes, xenon population, and delayed neutron precursors. This work introduces the lumped 3D modeling approach for core geometry and uses an improved heat transfer correlation, validated through Computational Fluid Dynamics (CFD) analysis. Furthermore, transient safety simulations using the complete model are presented, showcasing its robustness in capturing complex reactor dynamics and ensuring safety under various operating conditions.