Yuanzineng kexue jishu (Aug 2022)
Experimental Investigation on Reflooding Behavior in Annular Rod Bundle
Abstract
The internally and externally cooled annular fuel is one of the innovative fuel geometry proposals for advanced PWR, which could provide a substantial increase of power density while maintaining or improving safety margins. The quenching behavior of annular fuel during reflood stage in LOCA is significantly different from that of cylindrical solid fuel, owing to the coupling effect of dual-cooling. However, the experimental study focusing on quenching characteristics in annular fuel geometry is very little. In the present study, a bottom reflood experimental study on quenching behavior in a 3×3 external and internal cooled annular rod bundle was carried out by using self-designed indirect-heating annular rods to set up the experimental apparatus. The typical physical process and the effects of key parameters on quench during reflooding were studied in detail. The results show that the flooding process in annular rod bundle is similar to that of cylindrical solid rod bundle. The quench front propagation and the variation of heat transfer mode of both external and internal surfaces are almost synchronous. However, it is observed that there is a temperature gradient between internal and external sides of annular rods at the same time. The quench front propagation velocity increases with reflood velocity and inlet subcooling, while decreases with the increase of peak cladding temperature and linear power density. In addition, the quench front propagation velocity at the downstream of spacer grid is found to increase under the conditions of low reflood velocity, low subcooling and high cladding temperature.
