Review of Considerations for Molten Salt Reactor Off-gas Inventory Simulation

Liquid-fueled molten salt reactors present a complicated modeling problem due to the spatial distribution of radionuclides throughout the system. The mechanisms of transfer for species in the system vary widely depending on the location in the reactor. To accurately model the inventory in an off-gas system, all transfers throughout the system must be considered. In this document, following an introduction to fission products, a review of considerations for this modeling problem is presented. Modeling considerations are detailed, including discussion of the thermophysical properties such as volatility and solubility of species in molten salt. Mass transfer theory and applicable scenarios in molten salt, graphite, and helium bubbles is discussed following this. An extensive list of mass transfer correlations that may be applicable in molten salt reactor systems with explanations provided for each is also provided. The ability to detect species in an off-gas system is also discussed based on historical data. Lastly, a general framework for the numerical solution of the system is suggested along with future steps towards implementation of the methodology discussed.