M. Swinney, “Experimental and Computational Assessment of Trace Nuclide Ratios in Weapons Grade Plutonium for Nuclear Forensics Analysis”, Ph.D. Dissertation, Nuclear Engineering, Texas A&M University, College Station, TX (2015).
A terrorist attack using an improvised nuclear device is one of the most serious dangers facing the United States. The work presented here is part of an ongoing effort to improve nuclear deterrence by developing a methodology to attribute weapons-grade plutonium to a source reactor using an intrinsic physical signature. In order to replicate the neutron flux in a fast-spectrum reactor and obtain experimental samples emulating weapons-grade plutonium produced in the blanket of a Fast Breeder Reactor (FBR), depleted uranium dioxide samples were placed in a gadolinium sheath and irradiated in the High-Flux Isotope Reactor (HFIR) at Oakridge National Laboratory (ORNL). Previous work on this topic identified several fission products that could be used to distinguish between reactor types, specifically; 137Cs, 134Cs, 154Eu, 125Sb, 144Ce, 85Rb, 147Pm, and 150Sm along with the Pu-vector. This work presents results that show agreement between an MCNPX simulation of the HFIR and experimental results (gamma spectroscopy) with a percent error on the order of ~10% for 134Cs, 137Cs, 154Eu and 144Ce. Additional experimental results (mass spectroscopy) agreed to within 5% for the following isotopes: 85Rb, 147Pm, 150Sm, 154Eu, 148Nd, and 144Ce. Results obtained from simulations of an Indian Prototype FBR and a Pressurized Heavy Water Reactor (PHWR) are also compared with the results from the HFIR simulation and experiment to demonstrate a proposed methodology implementing a straightforward maximum likelihood calculation for attributing plutonium to a source reactor.