This report describes the characterization plan, methods, and results for light water reactor (LWR) Materials Characterization Center (MCC) spent fuel Approved Testing Material (ATM)-101. ATM-101 is spent fuel from H. B. Robinson, Unit 2, Assembly B0-5, a moderate-burnup, pressurized water reactor (PWR) fuel that released very small quantities of fission products and fission gas from the fuel during commercial operation.