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2025 ANS Winter Conference & Expo
November 9–12, 2025
Washington, DC|Washington Hilton
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The journey of the U.S. fuel cycle
Craig Piercycpiercy@ans.org
While most big journeys begin with a clear objective, they rarely start with an exact knowledge of the route. When commissioning the Lewis and Clark expedition in 1803, President Thomas Jefferson didn’t provide specific “turn right at the big mountain” directions to the Corps of Discovery. He gave goal-oriented instructions: explore the Missouri River, find its source, search for a transcontinental water route to the Pacific, and build scientific and cultural knowledge along the way.
Jefferson left it up to Lewis and Clark to turn his broad, geopolitically motivated guidance into gritty reality.
Similarly, U.S. nuclear policy has begun a journey toward closing the U.S. nuclear fuel cycle. There is a clear signal of support for recycling from the Trump administration, along with growing bipartisan excitement in Congress. Yet the precise path remains unclear.
Vedant K. Mehta, Zachary A. Miller, Dasari V. Rao
Nuclear Science and Engineering | Volume 197 | Number 8 | August 2023 | Pages 2161-2175
Technical papers from: PHYSOR 2022 | doi.org/10.1080/00295639.2022.2164150
Articles are hosted by Taylor and Francis Online.
Metal hydrides are being seriously considered for advanced nuclear reactor or microreactor applications due to their solid physical state and high hydrogen density. Using hydrides for autonomous applications poses several research and development challenges, one of which relates to neutron upscattering in the thermal energy regime. These hydrides, including zirconium hydride and yttrium hydride, result in a positive temperature coefficient of reactivity for several advanced reactor designs. In this study, we consider one such design that exhibits positive feedback from metal hydrides and thoroughly investigate the neutronic aspects of the core. Temperature reactivity coefficients for four fuels and two hydride moderator configurations are studied, and the total temperature coefficients are found to be positive for all designs, showing that this issue cannot be resolved simply by material variations. Accordingly, five epi-thermal absorbers were evaluated to demonstrate the feasibility of the excess positive feedback suppression in the core instigating from neutron energy spectrum shift. Following which, two promising burnable poison candidates are selected to investigate further throughout the core discharge. Promising results are shown for this core design, which can be extended to other hydride-moderated remote special-purpose reactor designs.