Fuel Fragment Jamming Inside Fuel Rods Following a LOCA

Abstract

The US nuclear industry is designing longer fuel cycles requiring fuel enriched beyond the current limit of 5 wt% and resulting in burnups beyond the current rod average limit of 62 GWd/MTU. As burnup increases, fuel fragments leading to potential issues caused by fine fragmentation, relocation, and dispersal (FFRD). Following a LOCA, burst of high burnup fuel rods could disperse fine fragments into the fuel assembly coolant channels, which can challenge core cooling. The amount of fuel dispersal will be limited by fuel fragment interactions upstream of the burst opening that can lock or form a bridge across the opening. A review of available literature on particle jamming is presented to demonstrate that dispersal of high burnup fuel fragments upon burst following a LOCA will be limited by this phenomenon.