An experimental study of quenching propagation along narrow rectangular channels

Plate-type fuel assembly is employed in the miniaturized nuclear reactor and submarine, and it is essential to investigate the flow and heat transfer during reflooding for safety analysis. In this paper, an experimental apparatus is established to perform bottom reflooding in multi-rectangular channels. The heat transfer and flow regimes in the 3.2 mm width gap in the process of quenching are investigated based on the visualization results captured by a high-speed camera, and the thermal parametric effect on quench front propagation velocity is also studied. The result shows that the ratio of quench front propagation velocity to reflooding rate reaches the maximum when the reflooding velocity reaches 5 cm/s, and the rising trend of quench front velocity is weakened. Quench front velocity is influenced by pressure significantly while almost not affected by subcooling at a system pressure of 0.3 and 0.5 MPa. A prediction model of quench front velocity for rectangular channels is built based on the experimental result in this paper. Good agreement is obtained with ±30% uncertainty when comparing the predicted and experimental quench front propagation velocity.