b'MiniFuel Irradiation of Monolithic FuelsPrincipal Investigator: Christian PetrieTeam Members/ Collaborators: Annabelle Le Coq, Dylan Richardson, Chris Hobbs, Grant Helmreich, Joseph Burns and Jason HarpThis is the firstQ ualification and deploymentaccomplished by reducing the volume of any new fuel requiresof the fuel and packaging the miniature irradiation of monolithicrigorous irradiation testing fuel specimens inside individually ceramic fuels using theto demonstrate performancesealed capsules. By ensuring that the MiniFuel vehicle, whichunder representative normal andtotal nuclear heat generated inside offers high throughput,off-normal operating conditions.each capsule is dominated by gamma economical, separateThe traditional approach for quali- heating in the structural compo-effects irradiationfying new fuels requires exhaustivenentsas opposed to fission heating testing capabilitiesexecution of many integral fuel tests.in the fuelthis allows for a flexible with rapid burnupHowever, due to the long timeframeirradiation vehicle that can accommo-accumulation to for executing these integral testsdate a wide range of fuel compositions, support accelerated and the limited number of availableenrichments, and even geometries. fuel qualification. materials test reactors, this approachThe small size of the fuel also greatly is becoming impractical. To accel- reduces temperature gradients, which erate the timeframe to qualify newallows for near-isothermal conditions. nuclear fuels, a new approach is beingThe first MiniFuel irradiations that developed that relies on modernwere performed tested sol gelderived modeling and simulation tools touranium nitride kernels and tristruc-rapidly identify parameters with atural isotropic (TRISO)-coated particle high impact on fuel performance andfuels. While particle fuels are being a large uncertainty. This data will allowconsidered as an advanced fuel form for proper prioritization of targeted,for both light water reactors (LWRs) separate effects irradiation experi- and various advanced reactor concepts, ments. To this end, Oak Ridge Nationalthe ability to test monolithic fuels such Laboratory (ORNL) developed theas doped and undoped UO 2 , as well as MiniFuel irradiation vehicle for use inother ceramic fuels, is critical to evalu-conducting accelerated separate effectsating more near term accident-tolerant irradiation testing of a wide range offuel (ATF) concepts and to support nuclear fuel materials in the High Fluxburnup extension. This work repre-Isotope Reactor (HFIR) [1] sents the preparation and assembly of Project Description: the first set of monolithic MiniFuel Separate effects irradiation tests areirradiations, which included U 3 Si 2and designed specifically to isolate thereference UO 2disk specimens [2].most impactful fuel performanceAccomplishments:variables and provide experimentalTwo irradiation targets containing data to fill these critical gaps in the fuela variety of UO 2and U 3 Si 2disk performance models. The MiniFuelfuel specimens were fabricated and irradiation vehicle allows for highlyassembled for irradiation to targeted accelerated burnup accumulation withburnups of 810 and 2840 MWd/minimal coupling between the fissionkg U. The target irradiation temperature rate and the fuel temperature. This isis 450550C. The UO 2fuel disks were 88 2020|AFC ACCOMPLISHMENTS'