Identification of fissile materials from fission product gamma-ray spectra

A new active–passive nondestructive assay technique has been developed to identify fissile materials by observing the gamma-ray emissions from induced fission products. This technique entails using a neutron source to induce fissions in unknown containerized fissile materials and to subsequently observe high energy peaks (>800 keV) in the fission product gamma-ray spectrum. Ratios of the observed peak intensities are then formed. The values of these ratios can be compared to calculated theoretical values to identify the fissile material. The present work focuses on the differentiation between 235U and 239Pu.