b'2.5 LWR FUEL SAFETY TESTINGDevelopment and Demonstration of a Methodology to EvaluateHigh Burnup Fuel Susceptibility to Pulverization under a Lossof Coolant TransientPrincipal Investigator: Nathan Capps (Oak Ridge National Laboratory)Team Members/ Collaborators: Ryan Sweet (Oak Ridge National Laboratory; University of Tennessee, Knoxville), Brian Wirth(University of Tennessee, Knoxville), Andrew Nelson (Oak Ridge National Laboratory) and Kurt Terrani (Oak Ridge National Laboratory)This methodology isF or economic reasons, the USa letter to the NRC Commissioners, nuclear industry is renewingthe staff specifically identified a need a first of a kind usingefforts to build a technicalto define the boundary of safe high fidelity Departmentbasis to extend rod average burnupoperation for key fuel design and of Energy (DOE) codeslimits above the current regulatoryoperating parameters, stating that to investigate Lightburnup limit of 62 GWd/MTU. Thethe staff is challenged to evaluate Water Reactor (LWR)primary driver is to increase pres- the acceptability of future fuel design High Burnup-relatedsurized water reactor cycle lengthsadvancements and fuel utilization phenomenon. to 24 months, reducing the numberchanges. As such, it can be concluded of fresh fuel assemblies and corethat HBFF and potential dispersal into design constraints, thereby makingthe reactor coolant system introduces core energy utilization more efficient.additional complications in LWR fuel However, fuel pellet fragmentationsafety evaluations.and pulverization, termed highProject Description:burnup fuel fragmentation (HBFF),It is not clear how much fuel will be has been observed in the high burnupsusceptible to HBFF; nor has there (90 GWd/MTU) Halden loss-of- been a methodology developed to coolant-accident (LOCA) integralevaluate fuel susceptibility to HBFF. test series. The issue gained attentionTo that end, the paper proposes an when fuel fragmentation and pulveri- analysis methodology to assess fuel zation were also observed closer to thesusceptibility to HBFF during LOCA current US regulatory limit during thescenarios. The work presented used US Nuclear Regulatory Commissionthe BISON fuel performance code to (NRC) sponsored out-of-core integralevaluate a representative pressurized test at Studsvik Nuclear in early 2011.water reactor fuel rod exposed to a This led to NRC concerns with poten- rod average burnup of 75 GWd/MTU. tial changes to fuel and core designsSensitivity studies investigated the relative to fuel pellet pulverization. Inimpact of the peak cladding tempera-94 2020|AFC ACCOMPLISHMENTS'