Nuclide inventory analysis and fission product monitoring for nuclear safeguards in molten chloride fast reactors

Fission product analysis offers a powerful means to real-time monitoring of fissile material evolution and sudden alterations in Molten Chloride Fast Reactors, where conventional safeguards techniques are challenged by continuously circulating fuel. In this study, time-dependent depletion simulations were employed using SCALE 6.3.1 with TRITON-Shift and ORIGEN to quantify fission product under varied operational scenarios, including once-through and breed-and-burn modes. The results demonstrate that Nd and Sm in the fuel salt serve as delayed indicators of shifting ²³⁵U/²³⁹Pu ratios, while Kr in the off-gas stream rapidly reflects changes in fissile isotope composition. Additionally, Xe proves effective for tracking overall reactor power despite its weaker dependence on specific isotopes. These findings establish that targeted fission product monitoring can capture both gradual compositional evolutions and rapid perturbations such as plutonium diversion, thereby offering enhanced operational awareness and safeguards confidence in advanced molten salt reactors.