Molten salt reactor transient analysis capability of proteus-Nodal

A nodal transport code PROTEUS-NODAL was developed for homogenized-assembly core analyses based on the PN and simplified PN methods as an option of the high-fidelity code PROTEUS to provide conventional fidelity solutions in a consistent framework. Recently, steady state and transient analysis capabilities were added to the PROTEUS-NODAL solver to analyze molten salt reactors (MSRs) with flowing fuel. The neutronics solvers were extended to account for the drift of delayed neutron precursors and their decay outside the core. A model for decay heat calculation was also developed to account for the fuel salt flow that leads to partial release of the decay heat outside the core. A simple thermal-hydraulics model was implemented for thermal feedback calculation by representing the core as multiple parallel channels in the axial direction. The intermediate heat exchanger is modeled to simulate the heat removal rate by the intermediate loop. Using the calculated temperature profile at the end of each time step, the microscopic cross sections are updated by interpolating the pre-calculated cross section tables with the MC²-3 code. The developed MSR analysis capabilities of PROTEUS-NODAL were tested using the molten salt fast reactor (MSFR) benchmark problem. Transient analyses were performed for several unprotected transients including transient overpower, loss of flow, pump over-speed, loss of heat sink, and fuel salt over-cooling accidents. The power evolution agreed well in shape and magnitude for all transients with the reference results reported in other studies.