SUMMARY

Recent work on new nuclear reactors has focused on Generation IV designs, which includes molten salt technologies. One type of molten salt reactor with a solid fuel form is a fluoride salt-cooled high-temperature reactor. A prismatic fuel design of this type is the Advanced High Temperature Reactor (AHTR). AHTR uses hexagonal fuel assemblies that contain fuel plates embedded with TRISO fuel particles. The geometry of the AHTR fuel assembly is complex to model, so many previous studies have used simplifications to make simulations more feasible. This work created a parameterized multiphysics framework of the 3D AHTR core to allow for both ease of design change and detail in simulations, all while remaining practical using typically available computational resources. Detailed simulations were executed using the Monte Carlo code Serpent with key features including criticality search, depletion, and multiphysics capabilities coupling neutronics with materials property changes (thermal expansion and heat conduction) and thermal hydraulics. These areas were incorporated into a novel AHTR-specific framework called ATOMICS, which was used to conduct several sensitivity studies and depletion simulations. Results demonstrated the impact of model refinements made possible by ATOMICS as well as provided information for potential future design changes made to AHTR. Despite AHTR being a large system susceptible to spatial numerical instabilities, the depletion processes used by ATOMICS were shown to be mostly numerical stable for the cases considered when appropriate methods and options were used. ATOMICS is a practical and flexible tool enabling realistic analysis of AHTR for statepoint and depletion simulations on conventional computing environments.