Nuclear and dosimetric features of an isotopic neutron source

Abstract A multisphere neutron spectrometer was used to determine the features of a 239 PuBe neutron source that is used to operate the ESFM-IPN Subcritical Reactor. To determine the source main features it was located a 100 cm from the spectrometer which was a 6 LiI(Eu) scintillator and 2, 3, 5, 8, 10 and 12 in.-diameter polyethylene spheres. Count rates obtained with the spectrometer were unfolded using the NSDUAZ code and neutron spectrum, total fluence, and ambient dose equivalent were determined. A Monte Carlo calculation was carried out to estimate the spectrum and integral features being less than values obtained experimentally due to the presence of 241 Pu in the Pu used to fabricate the source. Actual neutron yield and the mass fraction of 241 Pu was estimated.