Effective water cooling of very hot surfaces during the LOCA accident

Highlights: • Quenching velocities and rewetting temperatures are strongly dependent on the initial wall temperature. • With increasing initial wall temperature the quench front velocity rapidly decreases. • Value of the heat transfer coefficient is not in general dependent on the initial wall temperature and set coolant flow rate. • Increasing initial wall temperature goes with significant pressure bumps. - Abstract: The quench front propagation in the case of the water emergency cooling of water cooled fusion nuclear components is studied during the LOCA accident. In the case of the LOCA accident, heat removal can be successful only when water rewetts the surface. The place where water meets the very hot surface is called the quench front. The quench front propagation depends on the initial wall temperature, coolant flow rate, and heat accumulated in the cooled components. Results of the quench front experiment in an annular 1.7 m length channel with initial wall temperatures within the range from 250 °C up to 800 °C and coolant mass fluxes 100 kg/m² s and 180 kg/m² s are presented. From the results is concluded, that quenching velocities and rewetting temperatures are strongly dependent on the initial wall temperature as well as the pressure spikes. The behaviour of the heat transfer coefficient at the quench front is analyzed.