Destructive and nondestructive analyses have been performed on two irradiated UO<sub>2</sub> fuel samples with different irradiation histories to further develop attribution methods which may be applied to separated Pu. The first fuel sample was irradiated to a burnup of 4.4 ± 0.3 GWd/MTU in a pseudo-fast spectrum of neutrons in the High Flux Isotope Reactor (HFIR) reactor at Oak Ridge National Laboratory, and the second fuel sample was irradiated to a burnup of 0.97 ± 0.03 GWd/MTU under a thermal spectrum of neutrons in the University of Missouri Research Reactor (MURR). Analyses have focused on measuring key actinide and fission product isotope ratios within each fuel sample which may be used with a maximum likelihood approach to determine the most likely irradiation history of each fuel. The use of isotope ratios makes this approach agnostic to the separation history of the fuel. The analytical techniques employed to measure these ratios include nondestructive gamma spectrometry, as well as destructive analysis via ICP-MS after a chemical separation by cation exchange chromatography employing α-hydroxyisobutyrate as an eluent. The resulting chromatogram allows each isotope ratio of interest to be measured without experiencing isobaric interference from other elements sharing the same mass to charge ratio. Each isotope ratio measured is compared to simulated values produced by modelling both sample irradiations using state-of-the-art Monte Carlo radiation transport code, MCNP6. In general, there is good agreement (within 20%) between the measured and simulated ratios. These ratios will be used to determine the most likely irradiation history of each fuel sample, which will then be compared to the known history.

Measuring key isotope ratios in two irradiated UO<sub>2</sub> fuel samples for the attribution forensics of separated Pu

256th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.

Measuring key isotope ratios in two irradiated UO2 fuel samples for the attribution forensics of separated Pu

Measuring key isotope ratios in two irradiated UO₂ fuel samples for the attribution forensics of separated Pu