b'leak in the mixed oxide (MOX)specimen. These tests have been experiment capsules, after prototypegoing through advanced charac-testing and four successful capsules,terization described in another that finally resulted in rebuildingarticle in this report. Finally, this those experiments with some verypast summer the whole engineering simple design updates. package came together across the Overcoming each of these obstaclesfabrication shops, instrumentation and more, were enormous successeslaboratory, the TREAT transporta-along the way, which matured thetion cask, and three major nuclear TREAT teams to gain efficiencyfacilities to assemble two THOR in working through high stakescapsules with both high burnup challenges. Even more notable, theMOX and metal fuel pinsalso story of THORs eventual successdocumented in more detail else-as a proven device is proven bywhere in this report. One irradiated highlights of: 1) achieving anmetallic fuel test was returned to the engineered design that fully meetshot cell prematurely due to heater strict performance requirementscable issues and a necessary push developed jointly between JAEA andto complete the following MOX INL; 2) The successful irradiations ofexperiments prior to upgrading fresh U-10Zr fuel pins that providedthe TREAT core to support larger power validation of the blind reactorexperiments. The following MOX physics calculations and validatedexperiment was irradiated in July the special thermal design of the2022 to complete the THOR test system in 2021; 3) The followingplatform and a level 2 milestone.irradiation of a pressurized, freshLooking ahead, the team is already EBR-II driver fuel pin and a metallicimplementing minor but impactful fuel pin with the first infrareddesign improvements to ensure pyrometer inserted into a nuclearvery high performance of the THOR fuel in August 2022. These testscapsule, to execute several more fully bore witness of the awesomeTHOR experiments in 2024 in the TREAT hodoscope capability tolarger test containment upgrade measure fuel motion in-situ, givingnow deploying into TREAT. THORs truly unique insights into the truefuture entails a line of planned nature of even the worst conceivableusers, assuring its place in helping reactor conditions (see Figure 4). TheTREAT meet its national strategic instrumentation showed its worthmission of realizing advanced in precisely identifying the momentnuclear energy.of fuel failure during the experiment while providing 3-d mapping of the driving thermal conditions of the 2023|AFC ACCOMPLISHMENTS 19'