Thermal/Fast Fission Yield Ratio Signature for Neutron Interrogation of Nuclear Materials

Fission product yields were used to certify the enrichment of natural uranium sample by performing a comprehensive study of the yield pattern of some fission products formed in thermal neutron-induced fission of 235U and fast-induced fission of 238U, which relies on delayed gamma-ray measurements from short-lived fission products. The present experiment was conducted to demonstrate the utilization of Am‒Be isotopic neutron source as an active neutron interrogation source to provide information on thermal and fast neutron-induced fission on 235U and 238U, respectively. Natural uranium sample was used and certified. The fission products produced by these irradiations were analyzed using high purity germanium detectors resulting in valuable information of 13 short-lived radionuclides with half-lives ranging from a few minutes to several days. This method makes possible to use of differences in fission product yields ratios between them to identify fissile and fertile compositions of uranium material.