Molten Salt Reactor Safeguards: The Necessity of Advanced Modeling and Simulation to Inform on Fundamental Signatures

Oak Ridge National Laboratory (ORNL) have identified a number of previously-reportedi,ii technical factors impacting the implementation of safeguards for Molten Salt Reactors (MSRs), which include: (1) the homogeneous mixture of fuel, coolant, fission products, and actinides; (2) continuous variation of isotopic concentrations in the fuel salt, including removal (passive or active) of fission products, rare earth elements, and noble metals; (3) the potential for online reprocessing whereby some fraction of the inventory can be removed while the reactor is operational; and (4) unique refueling schemes including the ability to continuously feed the core with fresh fissile or fertile material. This necessitates the use of advanced modeling and simulation for tracking the isotopic masses and signatures (i.e., chemical, elemental, isotopic, and radiation) throughout the reactor and associated auxiliary processing, and importantly, as a function of time as the fuel salt evolves during reactor and fuel cycle operations.In the paper, an insight is presented into the necessity of advanced modeling and simulation methods and tools, highlighting the tight coupling between the reactor and fuel cycle operations, and the resulting fuel inventory and associated signatures. Using TRANSFORM—an ORNL-developed tool designed to model dynamic, complex systems such as salt-fueled MSRs (e.g., source term accountancy)—several scenarios are presented that demonstrate the data and modeling fidelity required and highlights the physical behavior of the four critical factors identified above, illustrating the need to capture the tight coupling between MSR behavior and safeguards assessments. A preliminary evaluation of the implications for safeguards technology development will also be presented.Endnotesi IAEA Emerging Technologies Workshop 2016ii IAEA Safeguards Symposium 2018