2017 | AFC ACCOMPLISHMENTS 159 characteristics. For instance, internal gas pressure, cumulative damage factor (CDF), irradiation damage (DPA) of load-bearing internal structure could be reduced because of lower temperature and further distance from the active fuel.These impacts are all positive to increase fuel residence time (i.e., burnup) and reactor lifetime. However, as tradeoffs, additional shielding is needed to protect upper internal structures and reduce activation of secondary sodium in intermediate heat exchanger. In addition, extra transient tests are needed because the annular fuels have different failed fuel symptoms and melting behaviors during transient scenarios. Accomplishments: Impacts of the annular fuel on internal gas pressure, CDF, and irradiation damage of load-bearing grid plate were evaluated using the 1000 MWth Advanced Burner Reactor (ABR-1000). In this study, fuels were replaced with the annular fuels and the gas plenum pf each fuel pin was located below the active fuel. However, other design parameters such as pin diameter, fuel composition and smeared density, discharge burnup, etc., were retained. The relocation of gas plenum below active fuel reduced fission gas temperature by 155K, which reduced hoop stress by 33% and increased time to cladding-rupture (i.e., CDF=1) by a factor of 12.4.Thus, the annular fuel can reside in the core longer than solid fuel, which is good for ultra-high burnup fuel. It is noted that the DPA of load-bearing internal structures such as a grid plate is one of the factors to determine reactor lifetime. In the annular fueled SFR, the grid plate could be further away from active fuel because of a lower gas plenum, which is good to reduce the irradiation damage. In order to compare the irradiation damage of the grid plate, Monte Carlo (MCNP) models were developed using full ABR-1000 assemblies using annular and solid fuels.The resulting DPA with annular fuel is about ~5% smaller than that with the solid fuel. Figure 1. Schematic overview of the Impacts of Annular Fuel on Reactor Performance.