Effect of chromium coated zircaloy cladding of accident tolerant fuel on the best estimate LOCA methodology

Abstract

The effect of chromium coating on zircaloy cladding for LOCA was systematically analyzed using MARS-KS code for Zion plant and FEBA reflood experiment. The equivalent material properties were derived, and they were higher than bare zircaloy cladding, which yielded higher PCT for blowdown phase. Through literature survey, CHF of chromium coated cladding was found to be 0.67 to 1.80 of bare zircaloy cladding, and film boiling heat transfer was 0.6–1.0. And the effect of the heat transfer change before/after critical heat flux such as nucleate boiling, transition boiling, and film boiling were also considered. These changes were combined with uncertainty range of best estimate calculation method, and then applied to LOCA and reflood experiment calculation. For the least heat transfer case, the PCT largely increased and quenching was not fully achieved. Finally, the modification for best estimate loss-of-coolant accident analysis methodology was suggested.