Date of Award
Doctor of Philosophy
G. Ivan Maldonado
Brandon Grogan, Nicholas Luciano, Lawrence Heilbronn
This dissertation is an examination of the use of uranium-232 as a tracer in nuclear fuel. Decay daughters from 232U, particularly thallium-208, produce high energy gamma rays that, when added to uranium, may increase detectability in case of theft or diversion, but are also hazardous in high quantities. Previous studies of the 232U decay chain are examined. This work will go in to a dosimetry study to determine how hazardous varying levels of 232U are, and how to efficiently produce 232U in sufficient quantities.
A dosimetry study was performed to determine the dose hazards due to the addition of 232U to uranium. This dosimetry study determined that the concentration of 232U to add to uranium is between 100 parts per trillion. A production scoping study was performed to determine the preferred target materials for producing 232U via neutron irradiations. Calculations performed using SCALE 6.2 ORIGEN determined that 231Pa and 230Th are the optimum target materials, and that reactor irradiations are preferred. ORIGEN Calculations using flux spectra from the High Flux Isotope Reactor determined that 231Pa calculations that the optimum irradiation time is 2 HFIR cycles, yielding 0.35 grams of 232U per gram 231Pa. Thorium-230 irradiations yielded 0.15 grams 232U per gram 230Th after five cycles. Neutronics analyses examined the neutron spectra in targets modeled in MCNP, and determined that self-shielding is a concern that may reduce yield, especially in 230Th, lowering the yield to 0.1 grams after five cycles.
A study of 238Pu contaminated with 236Pu produced at the Advanced Test Reactor was also conducted base on work from the CSNR. This examined strategies for mitigating against 236Pu contamination by chemical removal of 232U. Only material irradiated close to the center of the ATR needed this extra processing, and only a few micrograms of 232U is recoverable. However, these small quantities may still have a use for small stockpiles or testing purposes.
Rhodes, Joshua H., "Analyses for the Production and Dosimetry of Adding Uranium-232 as a Tracer to the Uranium Fuel Cycle. " PhD diss., University of Tennessee, 2021.