Physical tool for Unprotected Loss Of Flow transient simulations in a Sodium Fast Reactor

This physical tool is described before presenting the comparison of its results with experimental tests results (static and dynamic aspects) for the thermalhydraulic behavior and with mechanistic SIMMER code results for the global core evolution (including neutronics) during an ULOF transient. Moreover, the flow evolutions obtained with this tool are demonstrated to be in good agreement with the Ledinegg's quasi-static theory regarding boiling stabilization possibilities or flow excursion. This tool is demonstrated to be capable of reproducing the magnitude of mass-flow rate, reactivity, power evolution during an ULOF with a discrepancy of less than 3% regarding the same transient simulated with SIMMER. It will be used for safety-informed design and stability analyses of fast reactor systems, allowing to emphasize main dominant phenomena and significant trends for safety assessment. In the future, this physical tool, associated to statistical treatments of the effect of uncertainties, will enable large sensitivity analysis studies.