LEU+ to HALEU nuclear fuel cycle transitions and dynamic reactor models

Understanding the nuclear fuel cycle is crucial when designing sustainable and efficient nuclear energy systems. This thesis studies timely transition scenarios for fleets of Micro Modular Reactors (MMRs), X-Energy Xe-100s (Xe-100s), and AP1000s where low-enriched uranium plus (LEU+) fuel delays the demand for high-assay low-enriched uranium (HALEU) for the TRi-structural ISOtropic (TRISO) fueled reactors through a greedy, random, and initially random then greedy deployment scheme to meet energy demand growths from the U.S. Department of Energy (DOE) and U.S. Energy Information Administration (EIA). Using the open-source code Cyclus to model fuel cycles and the Monte Carlo code Serpent to perform neutronics calculations for the Xe-100 and USNC MMR, the results show that the reactor deployment scheme impacts the separative work units (SWU) required to meet energy demand. The greedy scheme, which prefers the highest capacity reactors, leads to the most significant increase in SWU for AP1000 low-enriched uranium (LEU), while the random and initially random then greedy schemes result in more consistent increases across fuel types. By evaluating the masses of fresh and used fuel, SWU, the number of reactors, and how well each simulation meets the projected energy demand, this thesis provides a comprehensive understanding of the impact of reactor deployment schemes on the nuclear fuel cycle. Additionally, this thesis examines the computational complexity of reactor fuel trading and removes assumptions about reactor power. The Trading On-Demand (TOD) reactor reduces the number of instructions in a simulation by trading fuel only when needed, while the Dynamic Power Reactor (DPR) allows for flexible power output to mirror historical or projected capacity factors. The results show that improving reactor models and simulating fuel cycle transitions leads to more efficient reactor deployment and fuel cycle design.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Nuclear, Plasma, Radiolgc Engr

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Ryan, Nathan Sean

Contributors dc:contributor

• Munk, Madicken
• Huff, Kathryn D.
• Uddin, Rizwan

• Cyclus
• Triso
• Haleu
• Leu+
• Leu Plus
• Serpent
• Nuclear Fuel Cycle
• Memory Efficiency
• Dynamic Power
• Fuel Trading
• Reactor Deployment
• Advanced Reactors

Statement dc:rights

• © 2025 by Nathan Sean Ryan. All rights reserved.

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/129324

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F129324