Performance evaluation of DRACS system of molten salt reactors using a transient solidification model

Abstract

A transient solidification model was developed and coupled to ASYST code to simulate the transient behavior of the direct reactor auxiliary cooling system (DRACS) of the fluoride-salt-cooled high-temperature reactor (FHR) during the loss of heat sink (LOHS) accident. The model was firstly validated by comparing the experimental data with the simulation results that deriving from available heat transfer and friction factor correlations. The simulation results are found to be well-fitted with the experimental data. The transient solidification model successfully predicted the occurrence of solidification and the complete blockage of the heat transfer pipes in DRACSs. The solidified layer is found to be beneficial for the decay heat removal at the early stage of solidification, however, a sudden clog is found at the end stage of the solidification. Based on the simulation results, an optimization attempt was made to extend the failure time of DRACS by reducing the length of heat transfer tubes. The model is applicable to all the reactors where solidification may occur, such as other molten salt reactors (MSRs) and lead-cooled fast reactors (LFRs).