Nuclear Resonance Fluorescence of 235U

Nuclear resonance fluorescence is a physical process that provides an isotopic-specific signature that can be used for the identification and characterization of materials. The technique involves the detection of prompt discrete-energy photons emitted from a sample which is exposed to photons in the MeV energy range. Potential applications of the technique range from detection of high explosives to characterization of special nuclear materials. One isotope of significant interest is ²³⁵U. Pacific Northwest National Laboratory and Passport Systems have collaborated to conduct measurements searching for nuclear resonance fluorescence signatures of ²³⁵U below 3 MeV using a 220 g sample of highly enriched uranium. Nine ²³⁵U resonances between 1650 and 2010 keV were identified in the preliminary analysis. Analysis of the measurement data to determine the integrated cross sections of the resonances is in progress.