Nondestructive and destructive assay for forensics characterization of weapons-grade plutonium produced in LEU irradiated in a thermal neutron spectrum

• Published in: Annals of nuclear energy 2023-04, Vol.183, p.109645, Article 109645
• Main Authors: Martinson, Sean P., Garcia, Jenna R., Haynes, Isaac W., Saini, Simrun P., Wagner, Elisan R., Long, Grace R., Folden III, Charles M., Chirayath, Sunil S.
• Format: Article
• Language: English
• Subjects: Gamma radiation spectrometry; Low-burnup uranium; Mass spectrometry; MCNP validation; Nuclear forensics
• ISSN: 0306-4549; 1873-2100
• DOI: 10.1016/j.anucene.2022.109645

•Point validation of MCNP through nondestructive assay (NDA) and destructive assay (DA) of isotopic accumulation.•Nuclear forensic measurements and analysis of LEUO2 material irradiated in thermal neutron environment to estimate fuel burnup and time since irradiation.•Investigation of weapons-grade plutonium production signatures in nuclear fuel cycle. A post-irradiation examination (PIE) of an enriched uranium sample was performed to advance a nuclear forensics methodology, based on intra-elemental nuclide ratios. The PIE was carried out on a few milligrams of low enriched uranium dioxide (LEUO2) sample, irradiated to a burnup of 1 GWd/MTU. The PIE of the LEUO2 sample provided the concentration of selected plutonium and fission product nuclides (239Pu, 240Pu, 241Pu, 91Y, 95Zr, 95Nb, 103Ru, 133Cs, 134Cs, 135Cs, 137Cs, 136Ba, 138Ba, 140Ba, 140La, 141Ce, 144Ce, 149Sm, 150Sm, 152Sm, 153Eu, and 154Eu). The PIE supported validation of the MCNP (Monte Carlo N-Particle neutronics simulation code) predicted concentration of these nuclides in the irradiated LEUO2 sample. This study showed that most of the MCNP predicted nuclide concentrations were within 15% and several within 10% compared to the PIE results. Gamma and mass spectrometry of nuclides in irradiated LEUO2 enabled the determination of uranium burnup and time since irradiation.