Visualization of quench-rewetting phenomena of liquid-film falling during dryout and rewetting on fuel rods in high temperature and pressure BWR operating conditions

Thermal and hydraulic phenomena of the dryout and rewetting on a fuel rod were discussed, based on the transient process observed visually with the surface-temperature variations measured during the transition from dryout to rewetting with a high-speed CCD video movie under BWR-rated high pressure and temperature conditions of 7 MPa and ~559 K (~286°C) in a thermal-hydraulics experimental loop. Liquid film was observed falling under CCFL from the downstream spacer placed in upper side on the electrically heated rod after the dryout. The heater rod surface could be cooled with the liquid film falling in the early stage of the rewetting and then the surface temperatures recovered from unusually elevated levels with quench-rewetting.Graphical Abstract