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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.
T. H. Trumbull, D. R. Harris
Nuclear Technology | Volume 154 | Number 3 | June 2006 | Pages 350-360
Technical Paper | Radiation Protection | doi.org/10.13182/NT06-A3739
Articles are hosted by Taylor and Francis Online.
The effect of material homogenization on the calculated gamma-ray dose rate was studied for several arrangements of typical pressurized water reactor (PWR) spent fuel pins in an air medium using the Monte Carlo code MCNP. The models analyzed increased in geometric complexity, beginning with a single fuel pin; progressing to small lattices, i.e., 3 × 3, 5 × 5, and 7 × 7 fuel pins; and culminating with a full 17 × 17 pin PWR bundle analysis. The fuel pin dimensions and compositions were taken directly from a previous study, and efforts were made to parallel this study by specifying identical flux-to-dose functions and gamma-ray source spectra.The analysis shows two competing components to the overall effect of material homogenization on the calculated dose rate. Homogenization of pin lattices tends to lower the effect of radiation channeling but increase the effect of source redistribution. Depending on the size of the lattice and the location of the detectors, the net effect of material homogenization on the dose rate can be insignificant, or it can range from a 6% decrease to a 35% increase relative to the detailed geometry model.