SUBJECT: Ph.D. Dissertation Defense
BY: Abdalla Abou Jaoude
TIME: Thursday, October 26, 2017, 3:00 p.m.
PLACE: Boggs Building, 3-47
TITLE: Design of a Mixed-Spectrum Long-Lived Reactor with Improved Proliferation Resistance
COMMITTEE: Dr. Anna Erickson, Chair (NRE)
Dr. Bojan Petrovic (NRE)
Dr. Nolan Hertel (NRE)
Dr. Adam Stulberg (INTA)
Dr. Nicolas Stauff (Argonne National Lab)


Long-lived fast reactors have been proposed as a proliferation-resistant approach to spread nuclear technology across the globe. These small reactors can be factory produced at centralized locations then shipped to areas in need. They would remain sealed throughout their operating time, and returned to the manufacturing hub for decommissioning. This removes the imperative for newcomers to the nuclear field to develop dangerous enrichment or reprocessing technology. However, critics still argue these long-lived designs pose a proliferation risk in light of the large quantity of high-purity plutonium that they breed. A mixed-spectrum reactor (MXR) configuration is proposed in this thesis as a potential solution to this challenge. Moderating material in the form of ZrH1.6 is inserted into the outer core region to reduce the plutonium quality. Inner and outer assemblies are then shuffled to ensure all fuel rods are exposed to the thermalized spectrum. Results show that the proposed concept can maintain a long-lifetime of around 25 years, while ensuring all bred material is below the weapon-grade limit. Safety evaluations concluded that similar performance to previous long-live designs can be expected. One notable additional advantage of the MXR is its substantially reduced peak fast fluence limit at the clad level, rendering the design more feasible than alternatives. Modeling these mixed-spectra configurations is challenging with typical deterministic codes such as REBUS, due to inherent assumptions. Approaches to improve the modeling capabilities are discussed, alongside detailed analysis using the MCNP6 stochastic code. Design variants of the MXR that use mixed U-Th fuel, burnable absorbers and different moderating material are also investigated in the thesis.