Analyses for the Production and Dosimetry of Adding Uranium-232 as a Tracer to the Uranium Fuel Cycle

Author

Joshua H. Rhodes, University of Tennessee, KnoxvilleFollow

Date of Award

12-2021

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Nuclear Engineering

Major Professor

G. Ivan Maldonado

Committee Members

Brandon Grogan, Nicholas Luciano, Lawrence Heilbronn

Abstract

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.

Recommended Citation

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.
https://trace.tennessee.edu/utk_graddiss/6974