The online Burnup Measurement System (BUMS) of High Temperature Gas Cooled Reactor Pebble Bed Module (HTR-PM) is used to measure the gamma spectra of the fuel spheres during the fuel cycle. However, it focuses on only part of gamma rays and the corresponding nuclide activity, which are used to calculate the burnup. Therefore, the acquired data has not been sufficiently and explicitly utilized, which could have been used for validation of nuclide inventory analysis codes, estimation of irradiation history of fuel spheres and nuclear material accounting.