Novel methodology for the quantitative assay of fissile materials using temporal and spectral Î2-delayed Î3-ray signatures

0168-583X/$ see front matter 2011 Elsevier B.V. doi:10.1016/j.nimb.2011.05.013 ⇑ Corresponding author at: Department of Nuclea Tennessee, Knoxville, TN 37996, USA. Tel.: +1 510 642 E-mail address: [email protected] (B.L. Goldblum An analytical model for the generation of b-delayed c-ray spectra following thermal-neutron-induced fission of mixed samples of 235U and 239Pu is presented. Using an energy-dependent figure-of-merit to designate the spectral regions employed in the assay, the unique temporal b-delayed c-ray signatures are utilized to determine the fraction of 239Pu in a mixed U–Pu sample. By evaluating the b-delayed c-ray temporal signatures of both 235U and 239Pu within a 3 keV energy bin, traditional sources of systematic uncertainty in quantitative assay using b-delayed c-ray signals, such as self-attenuation of the sample and energy-dependent c-ray detection efficiency, are significantly reduced. The effects of the time-dependent Compton-continuum and growth of longer-lived nuclides on the quantitative assessment are explored. This methodology represents a promising extension of the conventional means of analysis for quantitative assay of fissile materials using b-delayed c-ray signatures. 2011 Elsevier B.V. All rights reserved.