On February 28, 2018, Ellen Margaret O’Brien successfully defended her PhD dissertation, Application and Validation of Multi-Physics Coupling to Model Los Alamos National Laboratory’s Routine Production RbCl-RbCl-Ga Target Stack. Ellen’s PhD committee consisted of her advisor, J. Michael Doster, and members, Igor Bolotnov, Ralph Smith, Matthew Stokely, and F.M. Nortier of Los Alamos National Laboratory.
Ellen graduated summa cum laude with her Bachelor of Science in Nuclear Engineering from North Carolina State University in 2014. She was awarded a Nuclear Energy University Program (NEUP) Fellowship by the U.S. Department of Energy to continue her studies in graduate school. As a component of her NEUP Fellowship program, Ellen completed an internship at Los Alamos National Laboratory (LANL). The experience at LANL led directly to her research for her dissertation work. During graduate school, Ellen has been selected to present her research at two ANS national conferences, one ANS topical meeting, as well as the 16th Workshop on Targetry and Target Chemistry. She also was inducted into Sigma Xi, the Scientific Research Honor Society. During the final year of her PhD work, Ellen is employed as a Graduate Research Associate at Los Alamos National Laboratory. She has chosen to continue at LANL in a postdoc position after graduation in May.
Abstract
O’BRIEN, ELLEN MARGARET. Application and Validation of Multi-Physics Coupling to Model Los Alamos National Laboratory’s Routine Production RbCl-RbCl-Ga Target Stack. (Under the direction of Joseph Michael Doster.)
The goal of this work is to successfully couple particle physics and computational fluid dynamics for the purposes of accurately modeling behavior exhibited by a multiphase molten salt target during radioisotope production. The specific geometry of interest is a routine production target stack containing two multiphase molten salt targets at Los Alamos National Laboratory’s Isotope Production Facility. In target fluids where density varies as a function of temperature, heat deposition will cause the fluid in the path of the particle beam to decrease in density, thus changing particle beam penetration.
The goal of this coupling is to reach a steady state solution that accurately depicts both particle beam interaction and fluid distribution behavior within a target under nominal operating conditions. MCNP is used to model particle energy deposition as a function of position. This energy deposition profile is imported into ANSYS CFX and utilized to simulate the thermal behavior of the target and fluid motion of molten target regions. Validation metrics were chosen to quantify the accuracy of multi-physics coupling for multiphase domains. Comparison of experimental and computationally predicted yields were used as an initial benchmark.
To provide an additional benchmark, experimental data providing information about the spatial energy distribution in downstream targets was compared to model predictions. Uncertainty quantification was performed where possible for specific system response quantities of interest and for experimentally obtained data.