Sensitivity Analysis of Thermophysical Properties of Molten Salts using a Molten Salt Demonstration Reactor Model in TRANSFORM

Molten Salt Reactors (MSRs) are currently of interest due to the push for smaller reactors that are easier to deploy and the need for sustainable energy around the world. Nuclear energy can play an important role in addressing the issue of energy inequality and climate change. One of the main obstacles to deploying MSRs is licensing. An important aspect to understand in terms of licensing is the uncertainty of the thermophysical properties of the molten salt at the beginning of the cycle and during normal operations and transients. MSRs have already been proven as a viable concept; two research reactors—The Aircraft Reactor Experiment and the Molten Salt Reactor Experiment—have been successfully built and operated at Oak Ridge National Laboratory (ORNL) in 1954 and from 1965-1969, respectively. In this research, an MSR design similar to the proposed Molten Salt Demonstration Reactor design from ORNL in the 1970s was modeled using the Modelica programming language-based TRANSFORM library. Ultimately, this work’s analysis addresses the impact thermophysical property uncertainty has on reactor behavior during steady-state and transient conditions. To explore the reactor behavior, a sensitivity analysis is performed of density, viscosity, thermal conductivity, and heat capacity through the parameter space. This was performed for steady state conditions and transient conditions including a reactivity insertion and partial flow blockage. This sensitivity analysis facilitates the study of the effect that uncertainty has on operation. From this analysis, it was found that varying the heat capacity had the most effect on the temperature by a wide margin, but even so no property was found to have a significant change to temperature when it was perturbed during both steady state and transient conditions. Based on these conclusions, molten salt developers and researchers should be reassured that the current uncertainty of the four thermophysical properties investigated here, density, thermal conductivity, heat capacity, and viscosity, are well within the bounds of safe operation.