b'The ATF-RIA-1 commissioning series includes six tests. The first test (ATF-RIA-1-Gamma) was a calibration test to determine the relationship between the energy generated in TREAT versus the energy generated within the rodlet fuel. The rodlet was constructed with fuel pellets of both 4.95wt% and 0.74wt% U235 so that an upper and lower bound could be determined for the core-to-specimen energy coupling. Gamma spectros-copy was performed on this rodlet to provide a measured quantity for the core-to-specimen energy coupling. The remaining ATF-RIA-1-A through E tests are planned with varying specimen energy deposition targets from ~500-1100 J/gUO 2and capsule initial temperatures from 20C up to 200C. These conditions will provide baseline assessment of fresh Figure 3. Assembly of ATF-RIA-1-AUO 2 -Zry fuel rods covering regula-capsule. tory limits for energy deposition during RIA, with varying anticipated failure mechanisms from no failure expected; to possible high tempera-ture embrittlement failure of the cladding or ballooning and burst of the cladding.Accomplishments: During fiscal year 2020, the MARCH-SERTTA experiment campaign completed the ATF-RIA-1-Gamma test in January of 2020. The capsule was disassembled in a glovebox at TREAT and the rodlet was sent for gamma spectroscopy. The gamma spectroscopy provided a measured result of the number of fissions that Figure 3. Assembly of ATF-RIA-1-A capsule. occurred during the test to calculate the TREAT core-to-specimen energy coupling. The measured and predicted results from the neutronic calculations using MCNP show very good agree-106 2020|AFC ACCOMPLISHMENTS'