Medical Physics Seminar – Friday, April 20, 2012
Measurement of 225AC and 223Ra Production Cross Sections and Thermal-Hydraulic Modeling of a RbCi/Ga Target Stack
John W. Weidner (student of Provost Paul DeLuca)
Xtd-5, LTC, U.S. Army, DTRA Stockpile Associate, Los Alamos National Laboratory, Los Alamos, New Mexico - USA -
Cross sections for the formation of 223,225Ra, 225Ac and 227Th by the proton bombardment of natural thorium targets were measured at proton energies of 800 MeV and below 200 MeV. The production cross section for 227Ac was also measured at 800 MeV. No earlier experimental cross section data for the production of 223,225Ra, 227Ac and 227Th at 800 MeV by this method were found in the literature. For proton energies below 200 MeV, the measurements of this work are in good agreement with previously published data and offer a complete excitation function for 223,225Ra in the proton energy range of 90-200 MeV. A comparison of theoretical predictions with the experimental data generally shows factor of two agreement. Results indicate that accelerator-based production of 225Ac and 223Ra at 800 MeV and below 200 MeV is a viable production method capable of increasing current annual yield by nearly two orders of magnitude.
Additionally, a thermal-hydraulic model of a RbCl and Ga target stack, which is used for routine production of the PET isotopes 82Sr and 68Ge at Los Alamos, was created using ANSYS CFX. This model simulates the in-situ temperature profile and buoyant convective fluid flow of the targets while subject to intense 100 MeV proton beams. The CFX model provides a foundation for additional and more expansive parameter sensitivity studies by the Los Alamos isotope production team as they seek to increase PET isotope production yields in the near term.