Simulation activity in support of LIFUS 5 new test section's design and test conditions setup

This work represents a contribution to the design of a new test section for the LIFUS 5 facility and for the definition of possible experimental test conditions. The new test section is required to study the thermal-hydraulic phenomena that are at the base ai HLM-water interaction in an axial-symmetric geometrical configuration. The SIMMER III code has been chosen as the reference code to perform these simulations because it has been specifically developed to perform reactor safety analysis of core disruptive accidents for Iiquid metal cooled reactors with fast neutron spectrum. The new experimental campaign can therefore be finalized to qualify the SIMMER III code for such phenomena. Two series of simulations were performed for the present work: the first was carried out by injecting water at the reference pressure of 40 bar (low pressure cases), while the second was performed with water at the reference pressure of 180 bar (high pressure cases). The effects of the variation of five different parameters are considered in detail for both the series: the cover-gas volume fraction in the reaction vessel, the orifice diameter, the inlet water temperature, the inlet water pressure and the LBE initial temperature. The main results show that, especially for the cases run with high water pressure and with a large orifice diameter, a backflow can be observed in the pipeline that connects the water tank with the LBE tank; this backflow allows the possibility of LBE solidification inside the pipe. In addition, the calculated water injection mass flow rate gives an indication of the operating range of the sensor needed to measure this value correctly during experimental tests.