Date of Award

6-2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Department of Engineering Physics

First Advisor

Abigail A. Bickley, PhD

Abstract

The accurate prediction of isotopic compositions in Sodium-Cooled Fast Reactors (SFRs) is essential for nuclear forensic analyses and international nuclear treaty monitoring, particularly with the increased global deployment of Generation-IV reactors. This research developed and validated a detailed computational model tailored specifically to the Prototype Fast Breeder Reactor (PFBR), employing advanced Monte Carlo neutron transport methods, sophisticated burnup modeling, and variance reduction techniques. Validation against empirical data from the Experimental Breeder Reactor-II confirmed the model’s accuracy, producing a comprehensive database of isotopic compositions across 301 assembly locations and 580 isotopes through the reactor’s initial operation and equilibrium cycle. The model identified potential false-positive scenarios for CTBTO radioxenon monitoring, highlighting conditions where standard reactor operations could mimic proliferation signatures. Additionally, the suitability of isotope 106Ru as an effective indicator for MOX fuel burnup was demonstrated. Investigations into operational parameters showed negligible isotopic impact from spatially varying fuel temperatures but identified measurable effects from coolant impurities, such as calcium and potassium, on isotopes like 39Ar. However, practical implications for treaty monitoring remained minimal due to very low production rates. This work significantly enhances computational modeling capabilities, providing validated isotopic reference data vital for accurate nuclear forensic analysis and reinforcing global nuclear security efforts.

AFIT Designator

FY25-AFIT-ENP-DS-J-002

Comments

An embargo was observed for posting this thesis on AFIT Scholar.
Approved for public release, distribution unlimited. PA case number 88ABW-2025-0706

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