Advanced Aqueous Reprocessing of Spent Nuclear Fuel: Optimizing Separation Efficiency and Proliferation Resistance for Sustainable Nuclear Fuel Cycles

The sustained global expansion of nuclear energy, driven by the imperative to decarbonize electricity generation and enhance energy security, has intensified the urgency of resolving the spent nuclear fuel management challenge. The current global inventory exceeding 400,000 metric tons of heavy metal continues to grow by approximately 10,500 MTHM annually, while no nation has yet commissioned a permanent geological repository for high-level waste from commercial operations. The legacy Plutonium Uranium Extraction process, though industrially mature, produces a separated pure plutonium stream that poses unacceptable proliferation risks and consigns long-lived minor actinides to high-level waste, complicating repository design and performance. This dissertation developed and applied a comprehensive computational framework to conduct the first unified multi-criteria comparison of four advanced aqueous reprocessing technologies-Co-Extraction, Uranium Extraction Plus, Grouped Actinide Extraction, and innovative Selective Actinide Extraction-across three evaluation pillars: technical performance, economic viability, and proliferation resistance. The integrated methodology coupled isotopic depletion analysis using ORIGEN within the SCALE code system with process flowsheet modeling analogous to the Argonne Model for Universal Solvent Extraction, discounted cash flow economic evaluation, Bathke Figure of Merit proliferation assessment, Multi-Attribute Utility Theory scoring, and weighted-sum multi-criteria decision analysis. Results demonstrated that GANEX and i-SANEX meet the stringent dual targets of greater than 99.5% actinide recovery and less than 0.1% lanthanide contamination, while COEX and UREX+ fall short of the lanthanide purity requirement. Sensitivity analysis identified nitric acid concentration as the most critical process parameter, with an elasticity index of -4.76 for separation factor response. Total plutonium mass increased 65.1% across the burnup range studied, with Pu-238 fractions remaining below the 6% heat barrier threshold. The breakeven uranium price exceeded $640/kgU, confirming that reprocessing is not economically competitive without externalities under current conditions. GANEX and i-SANEX demonstrated an 82% improvement in the Bathke Figure of Merit over COEX for proliferation resistance. Integrated multi-criteria decision analysis ranked GANEX first in both balanced and security-focused weighting scenarios, establishing it as the most promising technology for deployment in Generation IV fast reactor fuel cycles. These findings provide an evidence-based decision support framework for policymakers and technologists navigating advanced fuel cycle technology selection.