Advanced online fuel reprocessing simulation for thorium-fueled molten salt breeder reactor

Current interest in advanced nuclear energy and MSR concepts has enhanced demand in building the tools to analyze these systems. This thesis introduces a Python script, SaltProc, which simulates MSR online reprocessing by modeling the changing isotopic composition of an irradiated fuel salt. SaltProc couples with the Monte Carlo code, SERPENT 2, for neutron transport and depletion calculations. SaltProc capabilities include a generic geometry capable of modeling multi-region and multi-flow systems, time-dependent feeds and removals, and specific separation efficiency for each element or isotope removal flow. Generally applicable capabilities are illuminated in this thesis in three applied problems: (1) simulating the startup of a thorium-fueled MSBR fuel cycle to find equilibrium fuel composition (when multiplication factor of the full-core model and the U-233 concentration in the fuel salt are invariant in time); (2) determining the effect of the fuel salt irradiation with online reprocessing on MSBR operations; and (3) estimating MSBR fuel cycle performance by computing the Th-232 feed rate over 20 years of operation and comparing with available data.\n\nIn the first application, full-core depletion in the MSBR demonstrated that (1) equilibrium fuel composition could be achieved after 16 years and (2) the multiplication factor stabilizes after 6 years of operation. In the second application, fuel salt irradiation with simulated fission product removal and fissile/fertile feed causes considerable neutron energy spectrum hardening; this spectral shift has a problematic impact on safety parameters (e.g., temperature reactivity feedback, reactivity control system worth). In the third application, the average Th-232 feed rate throughout 20 years of operation is 2.39 kg/day or 100 g/GWh(e) which is a good agreement with other recent research. Problematic effects of neutron energy spectrum hardening during MSBR operation should be taken into account for neutronics, multi-physics, and fuel cycle performance analysis.