  A non-destructive, gamma-spectrometric method for verifying the plutonium
content of Pu-Be neutron sources has been developed. It is also shown that the
isotopic composition and the age of plutonium (Pu) can be determined in the
intensive neutron field of these sources by the ``Multi-Group Analysis''
method. Gamma spectra were taken in the far-field of the sample, which was
assumed to be cylindrical. The isotopic composition and the age of Pu were
determined using a commercial implementation of the Multi-Group Analysis
algorithm. The Pu content of the sources was evaluated from the count rates of
the gamma-peaks of 239Pu, relying on the assumption that the gamma-rays are
coming to the detector parallel to each other. The determination of the
specific neutron yields and the problem of neutron damage to the detector are
also discussed.
