Coupling fission yield measurements with theory to advance fission models
Abstract
Nuclear tests produce anthropogenic isotopes that provide the only definitive means by which to determine whether a nuclear explosion has taken place. Following a suspected detonation, fission and activation products are recovered to evaluate a forensic fingerprint with which to determine the design and composition of the device. Immediate, on-site decryption of these signatures has always presented a forensics team with a challenging task, in part due to limited fundamental knowledge of the fission processes that drive signature formation. The proposed research will improve fission product yield measurements by increasing the range of irradiation environments for which data are available, and by using advanced chemical separation techniques to isolate fission products. The acquired data will be used to improve theoretical models to advance the fundamental understanding of the fission process. Improved understanding of the fission process will enable predictive signature capability for systems that have not previously been considered. Radiochemical methods will be used to separate individual fission products and evaluate their beta activity using gas proportional counters. The use of beta spectrometry instead of gamma spectrometry removes uncertainties associated with gamma decay branching and coincidence summing. Fission product yields will be assessed for uranium-235 and plutonium-239 fission over a range of incident neutron or photon energies and in the presence of various flux poisons. Epithermal neutron energies will be particularly interesting to consider, since the significant number of quantum levels available to uranium-235 and plutonium-239 nuclei in these energy regions leads to differences in nuclear deformation upon excitation and, ultimately, differences in fission product yields. Sample irradiations will be completed using dense plasma focuses, critical assemblies, the USGS 1 MW TRIGA reactor or the TRIDENT laser at Los Alamos National Laboratory.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 16, 2019
- Source ID
- HDTRA11810015
Entities
People
- Jenifer Shafer
Organizations
- Colorado School of Mines
- Defense Threat Reduction Agency