Simulations of unprotected loss of heat sink and combination of events accidents for a molten salt reactor

The molten salt reactor (MSR) is one of the Generation IV reactors. The fuel is dissolved in the carrier salt and circulates in the loop. The technologies are different from that in the solid-fuel reactors. In this work, the attention is focused on development of safety analysis tool for the MSRs. A single channel model, a heat transfer model, a heat sink model and a liquid-fuel point kinetic model that takes into account the effect of circulation are employed. The validation of this code is done with the experimental data of pump coastdown and startup in MSRE. The unprotected loss of heat sink (ULOHS), combination of ULOHS and unprotected loss of flow (ULOF) are performed on the Molten Salt Actinide Recycler and Transmuter (MOSART). This work aims to study temperature fluctuation, corresponding power change, effect of flow delayed neutron precursors and temperature reactivity feedback in transient accident to examine the inherent safety design of MOSART. The transient results reveal that the large negative temperature feedback coefficients guarantee MOSART inherent safety and the range of temperature is within the safety margin in case of combination of accidental events.

► A safety analysis code is developed for the molten salt reactors. ► The validation of the safety analysis code is done with the MSRE experimental data. ► The MSRE experiment and theoretical results do not show any oscillations with time. ► The unprotected loss of heat sink (ULOHS) is performed on the MOSART. ► The combination of ULOHS and ULOF is performed on the MOSART.