b'3.1 FISSION ACCELERATED STEADY-STATE TESTINGFission Accelerated Steady-state Testing (FAST)Principal Investigators: Geoffrey BeausoleilTeam Members/ Collaborators: Nate Oldham, Bryon Curnutt, Kyle Gagnon, Chris Murdock and Randy FieldingFAST is positioning INLI n an effort to accelerate theexperiments), and, ultimately, very irradiation time for advancedlong irradiation times in order to and the DOE complexreactor fuels, a revised capsuleachieve high burnup targets (10-12 to be able to meet thedesign has been analyzed andyears for 20 % FIMA (Fission per modern demands ofdeveloped for the Advanced FuelsInitial Metal Atom)). These challenges technology research andCampaign (AFC). This designhave been addressed by the Fission development (R&D) forincorporates a highly enriched,Accelerated Steady-state Testing (FAST) nuclear fuel by reducingreduced diameter fuel pin that isexperiment design.irradiation times for fueldoubly encapsulated by two steelPhase 1 of the FAST experiments is up to ten times faster. capsules. This design alloys acceleratedfocused on alloy fuels for sodium fast irradiations and reduced sensitivity toreactors that are assembled for inser-fabrication variances and eccentricities.tion into the ATR during the 169A The capsule designs utilize existingcycle (November 2020). In total, there experiment baskets from the AFCare 28 experiments being inserted:capsules in the Advanced Test Reactor (ATR) outer A position (FAST-OA) Control specimens that compare and the ATF-1 capsules in the small Ito historical irradiation tests will position (FAST-SI). be used to understand the impact Project Description: of accelerated irradiation to fuel Previous advanced reactor fuels,performance. These pins are uranium namely fast reactor fuels, have beenwith 10 wt% Zr (U-10Zr), 75% successfully irradiated within thesmear density, and sodium-bonded Idaho National Laboratory (INL)solid pins in HT9 cladding.Advanced Test Reactor (ATR). Fuel Additives that contain antimony, However, these tests have had chal- tin, or palladium in order to mitigate lenges in that they require adjustmentslanthanide fission product attack on to the experiment design to make thethe cladding (fuel-cladding chemical power profiles more prototypic (intro- interaction [FCCI]). These are similar duction of a cadmium shroud), ato the palladium-bearing AFC-3A tight-tolerance helium bond betweenand AFC-3B tests but will be irradi-the cladding and the capsule wall (aated to higher burnups.low heat flux zone for increasing the Sodium-free annular fuel pins that cladding temperature to prototypicare thermally bonded with helium. temperatures), high sensitivity toThese are comparable to the helium-fabrication variances and eccentricitiesbonded annular fuel tests from (lower limit of fabrication tolerancesAFC-3A and AFC-3B but will be significantly affect the outcome of theirradiated to higher burnups.126 2020|AFC ACCOMPLISHMENTS'