Design and qualification of the bruce CANFLEX® low void reactivity fuel bundle - An overview

The Bruce NGS B reactors are currently restricted from 100% full-power operation due to the licensing issue related to the safety margins during a postulated large break loss-of-coolant accident (LOCA). In order to assist Bruce Power to restore the reactor power, Atomic Energy of Canada Limited has designed a new fuel bundle that will improve the safety margins by reducing the coolant void reactivity during a LOCA. The Bruce CANFLEX® low void reactivity fuel (LVRF) bundle consists of dysprosium-doped natural uranium in the central element of the fuel bundle and slightly enriched uranium in the inner, intermediate and outer rings of the bundle. The 43-element CANFLEX bundle design, with its critical-heat-flux enhancement appendages, will also provide higher critical channel power. This has the additional benefit of mitigating the reductions in critical channel power caused by the pressure tube creep when the reactor ages. Prior to the loading of the LVRF bundles into the reactor, the fuel design must undergo fuel qualification activities to demonstrate the performance of the fuel bundle against the fuel design requirements. This paper provides an overview of the approach and activities in the design and qualification of the Bruce CANFLEX LVRF.