b'tFGR Measurement and In-Cell DemonstrationPrincipal Investigator: Yong YanTeam Members/Collaborators: Jason Harp, Chuck Baldwin, Bob Morris, Nathan Cappsfiscal year (FY) 2022 [7]. This milestone report summarizes the tFGR deploy-ment and the first in-cell tFGR test using the irradiated high burnup fuel.Project Description:The goal of the integral testing is to capture the onset temperature of tFGR and the amount (moles of gas) of tFGR for a fuel segment experiencing a representative LOCA transient. This release is measured while the fuel is under mechanical constraint by the cladding and under representative fuel pin internal pressure before the segment bursts. For the ORNL approach, the irradiated fuel will be Figure 1. Schematic diagramT he transient fission gas releasecut into segments 15 to 30 cm long. of SATS tFGR facility for real- (tFGR) during the temperatureThese segments can be refabricated time tFGR measurement increase associated with a loss- with end caps and connected to a of-coolant accident (LOCA) in light- pressurization system. The tFGR water reactors (LWRs) is a significantsystem is coupled with the ORNL Severe Accident Test Station (SATS) This new system willcontribution to the total pressure in aand builds upon previous ORNL evaluate critical gaps infuel rod and may cause an unexpectedexperience with the Core Conduction tFGR behavior for fuelrod burst. The lack of data related toCooldown Test Furnace [8]. During the segments experiencingtransient fission gas (tFGR) continuesSATS LOCA test, the segment will be simulated LOCA events. to be a key gap in understanding LWRstepwise heated to a temperature at a cladding burst behavior under LOCAspecified ramp rate, and the content conditions [16]. To fully characterizeof the segment will be expanded into this behavior, tFGR data must bea larger volume and sent to the fission collected from several differentgas traps out-of-cell at atmospheric systems. The available data suggestspressure. There, the content will be that tFGR testing must be performedevaluated by counting the released under fuel-pin-relevant pressure (~10krypton-85 content. The test will MPa) to be characteristic of in-pilethen proceed on to the next hold conditions [26]. Oak Ridge Nationaltemperature until the final tempera-Laboratory (ORNL) has developed ature is reached. Alternatively, the system to measure the integral tFGRfuel segment could be heated under from irradiated fuel segments. Therepresentative LOCA ramp and then system design, testing capabilities,capture the total amount of tFGR and construction were reported inreleased by the sample.94 2023|AFC ACCOMPLISHMENTS'