NERTHUS thermal spectrum molten salt reactor neutronics and dynamic model

There are several Molten Salt Reactor (MSR) designs which are currently in development by various companies and institutions. However, many researchers, developers, and communicators in the nuclear industry are unfamiliar with the unique qualities and behavior of MSRs. To help remedy this issue, the NERTHUS combined neutronic and dynamic models are intended to be a tool for simulating generic MSR behavior under a variety of scenarios. The design of the models was inspired by that of ThorCon’s TMSR-500 and utilizes many features and the same topology as the Molten Salt Reactor Experiment (MSRE). NERTHUS’s neutronics model simulates a four year depletion cycle with refueling for any user-defined fuel salt, and includes the ability to perform feedback and control rod worth calculations. The point kinetics parameters at any stage of the burn-up simulation can be used to model various transients using the dynamic model. The NERTHUS dynamic model is a full y integrated model of a MSR power plant up to the balance of plant. It features two salt-to-salt heat exchangers, a once-through steam generator, it can track decay heat and fission product poisons, and it utilizes a modular ‘plug and play’ design. The dynamic model is lightweight and can simulate nominal and off-nominal transients relating to heat transfer through the system with simulation speeds of one minute simulated per few seconds actual. This paper details results from a FLiBe fuel salt [LiF-BeF2-UF4 (72-16-12 mole%)], and a “ThorCon” fuel salt [NaF-BeF2-ThF4-UF4 (76-12-9.5-2.5 mole%)]. The NERTHUS neutronics and dynamics models were made to be an educative tool to help researchers and students investigate and learn about MSR behavior. As such, it is freely available on GitHub.