Signatures of fissile materials: high-energy γ rays following fission

Abstract The spectral and temporal dependence of β-delayed γ rays in the range E⩾3.0 MeV from thermal–neutron-induced fission are shown to be characteristic signatures of 235 U and 239 Pu . For the interrogation of large sea-going cargo containers filled with hydrogenous materials, β-delayed γ rays can offer an increase in sensitivity for the detection of these and other fissile materials by as much as 10 3 –10 4 compared to the detection of β-delayed neutrons.