Experimental Study on Coupled Quenching Behavior in a Dual-Cooled Annular Rod Channel

In this paper, a bottom reflooding experiment was performed in a single annular rod channel to investigate the coupled quench characteristics of the dual-cooled annular fuel. An indirect-heated annular rod with the axial uniform power shape was used. The asymmetric quench front propagation between the external and internal sides of the annular rod was observed. The internal cladding was quenched earlier than the external cladding, owing to heat accumulation in cylindrical shell and the blockage of the vapor flow by the grid spacers in external channel. A unique "secondary quenching" phenomenon was observed at the internal side of annular rod due to the radial heat conduction. The effects of reflooding velocity, inlet subcooling, initial cladding temperature and heating power on quenching behavior were also studied. The present study can contribute to the understanding of the coupled quenching characteristics of dual-cooled annular fuel and obtains valid data for the development of reflooding models and the validation of thermal hydraulics codes of annular fuel.