GNF FUEL RELIABILITY AND CHANNEL PERFORMANCE: 2019 UPDATE

摘要

The purpose of this paper is to provide an update tothe fuel reliability and channel performance of GNF fueldesigns for BWR applications – including inspectionobservations. Debris failures and channel-control bladeinterference continue to have the greatest impact on plantoperations. Details of the recent debris failures at RiverBend Station are provided. In addition, a strong case ismade that debris is entering the bundle through the lowertie plate during operation instead of the upper tie plateduring outages. Given this understanding of the source ofdebris, GNF has focused efforts on stopping debris fromentering the bundle during operation and stopping debrisfretting if debris does enter the bundle. In 2016, GNFintroduced full reloads of GNF2.02 with an improvedDefenderPLUS filter and spacers with fewer debriscapture sites, and in the first cycle of operation at RiverBend Station, a statistical improvement was observed forGNF2.02 compared to GNF2. GNF is also developing adebris-resistant coating called ARMOR that was part oflead test assemblies inserted in 2018. In addition, GNFplans to introduce a next generation filter design in 2020,which is expected to improve filter effectiveness evenfurther compared to the DefenderPLUS filter. Longerterm,GNF expects a full transition to GNF3, which wasdesigned to further improve fuel reliability while alsoincreasing fuel-cycle benefits over GNF2. Besides debrisfailures, PCI-type failures are the only other observedfailure type in the last decade, and these have been nearlyeliminated through advances in core design and customeradoption of the GNF fuel operating guidelines, butremain as a potential mechanism when specific, uniqueoperating conditions might occur. Observations ofchannel-control blade interference continue with the useof Zircaloy-2 and Zircaloy-4 channels, which emphasizesthe need to fully transition to reload quantities of GNF’sadvanced NSF channel material. NSF is the standardchannel material on the GNF3 fuel product line.