b"Experiments for In-Situ Microstructural EvolutionPrincipal Investigators: Nicolas Woolstenhulme and Colby Jensen (INL)Team Members/ Collaborators: C. Baker, R. Schley, C. Adkins, L. Sudderth, C. Hill, D. Chapman, S. Snow and H. Guymon (INL)This project hasT he Transient Reactor Testresearch. TREAT is not well-suited facility (TREAT) at Idahoto burnup or neutron damage National Laboratory (INL)accumulation, but examples of these successfully integratedwas constructed in the late 1950s,types of applications can make use of the objectives of twoprovided thousands of transientoscillating power histories for phase-DOE programs toirradiations before being placed inbased properties measurements and develop tools necessarystandby in 1994, and was restarted inin-situ characterization of fundamental to perform temperature2017 in order to resume its crucialirradiation behavioral changes under controlled irradiationsrole in nuclear-heated safety research.active fission. An innovative design in TREAT with advancedAdvances in modern computationalapproach to enable this type of testing instrumentation capablecapabilities and a resurgence of interestleverages the relatively low radioisotope of characterizingin novel reactor technology haveaccumulation during brief irradiations microstructural changescreated an opportunity for emphasizingby arranging small fresh fuel specimens for fundamentalmodernized science-based and separatein low activation hardware modules irradiation behavior ofeffects test capabilities at TREAT. Aso that they can be easily extracted metal fuels. high temperature heater module, anand shipped for examination within instrumented multi-specimen capsuleweeks. This concept, termed the train, and in-pile application of laserMinimal Activation Retrievable Capsule resonant ultrasound spectroscopyHolder (MARCH) irradiation vehicle were developed for TREATs modularsystem, was developed and deployed irradiation vehicle and demonstratedculminating in completion of TREATs in fiscal year (FY)19 to enablefirst fueled irradiation series in early continuation of this type of research on2018, the first fueled experiments since metal fuels. its shutdown in 1994. These first tests Project Description:were employed for pulse-type transient TREAT is typically thought of asheating of light water reactor rodlets a reactor best used for simulatingas foundational work for accidental postulated accidents with shorttolerant fuel (ATF) development duration extreme power maneuvers.but focused on engineering scale However, TREATs ease of accessperformance rather than enabling for in-situ instrumentation andin-situ microstructure-based irradiation collocation with fuel fabricationscience. Further work was performed and postirradiation examinationin 2019 under he Advanced Fuel (PIE) facilities also make it uniquelyCampaign (AFC's) advanced reactor capable for some niche fundamentalmetal fuels effort as well as Department irradiation science applications notof Energy's (DOE) newly formed typically associated with fuel safetyin-pile instrumentation (I2) program to address this capability gap.204 2019|AFC ACCOMPLISHMENTS"