Experimental investigation on mechanism of high-pressure subcooled water injecting into high-temperature medium under tube rupture accidents

[Background]: During the Steam Generator Tube Rupture (SGTR) accident of Lead-cooled Fast Reactors (LFR), liquid metals come into direct contact with water, resulting in a multiphase flow phenomenon involving liquid metal, water and vapor. [Purpose]: This study aims to investigate the transient pressure rise and multiphase heat transfer mechanisms resulting from a large quantity of coolant injection into liquid lead-bismuth eutectic (LBE) during the late-phase SGTR accidents. [Methods]: An experimental platform was established to simulate the injection of high-pressure subcooled water into high-temperature liquid lead-bismuth eutectic (LBE). The interaction phenomena between LBE and water were investigated under controlled conditions. Key experimental variables included injection direction, nozzle diameter, injection pressure, injection time, and thermal oil (simulating LBE) temperature. Pressure transients and temperature disturbances within the test section were systematically measured and analyzed. [Results]: Firstly, the temperature and pressure changes of two typical thermal oil temperature conditions were compared. The pressure impulse and temperature disturbance in the test section were obviously greater when thermal oil had heating effect on subcooled water. Secondly, increasing injection pressure, nozzle diameter and injection time could effectively increase the pressure impulse and temperature disturbance. Finally, based on the four thermal physical parameters, a prediction model of thermal oil pool temperature change was established. Under the conditions that the thermal oil temperature was higher than the water saturation temperature, the average error between the model calculation results and the test data was 10.2% while all errors were within ±30%. [Conclusions]: The results can provide a theoretical basis for the discovery of heat and mass transfer mechanism and the development of calculation model on the interaction between liquid lead-bismuth eutectic and water.