J.M. Osborn, S.S. Chirayath, W.S. Charlton, “Neutronics Analysis of Fast Breeder Reactor Core to Support the Plutonium Fingerprinting for Forensics (PuFF) Project”, INMM 54th Annual Meeting, 14-18 July 2013, Palm Desert, California, USA.
One of the objectives of this project is to use computational and experimental methods to determine the feasibility of reliably predicting and measuring a unique intrinsic physical signature in separated weapons-grade plutonium produced by certain reactors, specifically a fast breeder reactor (FBR) and CANDU-type (CANada Deuterium Uranium) thermal reactor. These reactor types will likely be operating in a non-safeguarded manner in some countries. Both the FBR and the CANDU reactor fuels produce weapons-grade plutonium when burned to low burnups of about 1000 MWd/MTU. However, the neutron energy spectrum differences in these reactors shall result in variations in isotopes of plutonium, minor actinides and fission products. The computational part of the project utilizes MCNPX-2.7 radiation transport code to model the reactor core, perform burnup cycles and estimate the resulting isotopics of actinides and trace elements in the discharged fuel. Characteristics that were evaluated when selecting the isotope signatures included the amount of production, half-lives, Plutonium URanium EXtraction (PUREX) decontamination factor, and the probability of detection. Results of the ratios of each selected fission product and actinide to the 239Pu produced in the fuel showed significant differences between the FBR and CANDU. Normalizing the isotopes of interest to the amount of 239Pu is suitable for the PuFF project because this aids in evaluating separated weapons-grade plutonium. The goal is, if smuggled weapons-grade plutonium is caught, analysis of intrinsic isotope signatures associated with it should be able to ascertain the type of reactor that produced it. Fuel samples will be irradiated with a replicated neutron spectrum at the Oak Ridge National Lab-High Flux Isotope Reactor (ORNL-HFIR), and then subject to a lab scale PUREX process to separate plutonium from fission products and uranium. Specific plutonium isotopes and fission products retrieved from the simulation results were investigated for correlations and will be compared with the experimental data when they become available in the latter half of this investigation. A separate abstract is submitted for the CANDU side of the PuFF project.