b'FGR calculations in addition to fully temperature-dependent microcracking-based FGR; the latter component was originally developed based on experimental results from power ramp tests. In this work, the model was exercised and evaluated under several temperature transient scenarios to fully assess its capabili-ties. BISON accounts well for the effects of temperature conditions and microstructural features on diffusion-controlled FGR. However, the model, which does not yet include a representation of FGR driven by fuel fragmentation during Loss of Coolant Accident (LOCA)-type transients, largely underesti-mates transient FGR in the consid-ered transient cases when compared with experimental data.Accomplishments:There has been a recent push to accelerate fuel qualification by devel-oping capabilities to reduce irradia-tion periods. This project looked to build on this push by using modeling and simulation to inform experimental development. The demonstration leveraged the Mini-Fuel irradiation capsule designed to irradiate mini fuel samples under isothermal temperature conditions. Steady-state irradiations involving MiniFuel effectively decouple the fuel temperature from the fission Figure 2. Evolution of FGR with burnup before and during the transient (top)rate (i.e., power), improving our and of FGR during the temperature transient compared to experimental FGRability to generate and understand data from Noirot et al. (2014), along with the fuel temperature (bottom)the microstructures observed in commercial reactor fuels. Further-74 2021|AFC ACCOMPLISHMENTS'