A long-term detection of the 871 keV gamma-ray emitted from two PuO2 samples (100 g recovered powder and 8 g pure powder) has been conducted with a high resolution HPGe spectrometer in a lead-shielded chamber. An on-site detection of the 871 keV gamma-ray emitted from 200 g recovered PuO2 powder has also been performed. Although the 871 keV peak can be observed in all 3 samples

other characteristic gamma-rays related to the existence of oxygen are not seen. The 871 keV peak is absent in spectra acquired from metal plutonium samples

which can answer whether the plutonium material in a sealed container is metal plutonium or plutonium oxide

i.e. the 871 keV gamma-ray can be an evidence for the absence of metal plutonium. The 871 keV peak is strong in the spectrum of 200 g recovered PuO2 sample. A software of plutonium abundance and age analysis developed by ourselves can identify the 871 keV peak from a spectrum of 10 min. If the system is appropriately improved

it can be used to detect attribute of plutonium oxide through identifying 871 keV gamma-ray peak.