The characterization data, obtained to date, for Materials Characterization Center (MCC) Approved Testing Material (ATM)-101, spent fuel from H.B. Robinson, Unit 2, Assembly B0-5, are described. ATM-101 consists of 27 equal-length segments from nine fuel rods. Characterizations provided for ATM-101 include: (1) reactor, assembly, and fuel rod descriptions; (2) Assembly BO-5 irradiation history; (3) a description of unusual incidents that occurred to the rods; (4) fission gas release measurements; (5) results of ceramography/metallography examinations; (6) fuel burnup measurement results and correlations; (7) results of gamma scanning; (8) calculated values of the radionuclide inventory; and (9) results of a radionuclide chemical overcheck. Calculations for and measurement of radial distributions of selected radionuclides are planned, but not scheduled. A description of pertinent results from other studies on sibling rods from Assembly B0-5 is also included. The distribution of ATM-101 to date is described along with characterization results on specially processed material. It is intended that this report be revised and updated as additional characterization data become available. 6 refs., 30 figs., 20 tabs.