b'1.4 CAPABILITIESATF-2 Historical AccomplishmentsPrincipal Investigator: David Kamerman Team Members/ Collaborator: Brian Durtschi, Nicolas Woolstenhulme, Bryon Curnutt, Travis Labossiere-Hickman,Richard Skifton, Fabiola CappiaWith less than halfAcontains a 23 array of test pins. The fully prototypic testing platform for testing newtiers are numbered 16, with Tier 1 light water reactor (LWR)at the bottom and Tier 6 at the top. of the reactors thataccident tolerant fuel (ATF) designsAt various times, two of the tiers are were available in thehas been established in a pressurizedcombined so that longer test pins can past, the United Stateswater loop in the center flux trap ofbe irradiated. The six tiers are joined LWR Testbed standsIdaho National Laboratorys (INLs)together with dovetail joints and held poised to supportAdvanced Test Reactor (ATR). Thein place by spring clamps. The flow the same diversity ofirradiation experiment, named ATF-2,area in the tiers when configured with test conditions andhas completed seven cycles of proto- standard 1717 pressurized water data needs to supporttypic steady-state irradiation of 45 testreactor (PWR)-sized fuel pins is ~2.677 development ofpins to burnups as high as 30 MWd/ cm 2 . This arrangement allows for the advanced LWR fuels kgU. Irradiation conditions have beendisassembly of the test train in the and materials. maintained via the Loop-2A pressur- ATR canal so that individual test pins ized water coolant loop and powercan be removed at various times in and fast-neutron flux histories of eachtheir irradiation life and be replaced of the fueled forty-one test pins haswith new fresh pins. The entire design been calculated using a combinedis modular, thus allowing for large Monte Carlo N-Particle (MCNP) andreconfigurable test matrixes.ORIGEN methodology. Accomplishments:Project Description: ATF-2 has irradiated 41 integral fuel The experiment design was requiredtest pins and 4 unfueled test pins for to support the irradiation testinga total of 45 test pins. The irradiation needs of multiple ATF developersinvolved 16 test pins with baseline Zr (e.g., fuel vendors)all of whomalloys, 23 coated-Zr alloys, and 6 test have slightly different technologies,pins with iron-chromium-aluminum development timetables, and irradia- (FeCrAl) alloys. All the integral tion testing needs. To accommodatefueled test pins contained UO 2fuel these changing test plans, the ATF-2pellets enriched to between 4.9 and test train was designed with six tiers4.95% U-235 and heavy metal densi-that are arranged axially over theties between 10.4 and 10.5 grams/length of the core. The incore portioncm 3 . Some UO 2pellets contained of the Loop-2A in-pile tube is approxi- sintering additives to increase their mately 122 cm tall, with a maximumgrain size and provide both improved test train diameter of 4.34 cm. Thefission-gas retention and better pellet ATF-2 test train fills this diameter andplasticity at high-temperature.consists of six tiers that are arrangedThe ATF-2 irradiation has completed axially in the core, each of whichseven steady-state ATR cycles,20 2022|AFC ACCOMPLISHMENTS'