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ANS Student Conference 2025
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Albuquerque, NM|The University of New Mexico
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Fusion Science and Technology
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General Kenneth Nichols and the Manhattan Project
Nichols
The Oak Ridger has published the latest in a series of articles about General Kenneth D. Nichols, the Manhattan Project, and the 1954 Atomic Energy Act. The series has been produced by Nichols’ grandniece Barbara Rogers Scollin and Oak Ridge (Tenn.) city historian David Ray Smith. Gen. Nichols (1907–2000) was the district engineer for the Manhattan Engineer District during the Manhattan Project.
As Smith and Scollin explain, Nichols “had supervision of the research and development connected with, and the design, construction, and operation of, all plants required to produce plutonium-239 and uranium-235, including the construction of the towns of Oak Ridge, Tennessee, and Richland, Washington. The responsibility of his position was massive as he oversaw a workforce of both military and civilian personnel of approximately 125,000; his Oak Ridge office became the center of the wartime atomic energy’s activities.”
Karl D. Hammond, Francesco Ferroni, Brian D. Wirth
Fusion Science and Technology | Volume 71 | Number 1 | January 2017 | Pages 7-21
Technical Paper | doi.org/10.13182/FST16-110
Articles are hosted by Taylor and Francis Online.
We analyze the effect of subsurface prismatic dislocation loops on the surface morphology and helium clustering behavior of plasma-facing tungsten through the use of molecular dynamics simulations that are moderately large in scale, consisting of approximately 830 000 atoms, and extend to times on the order of 1 μs. This approach eliminates some finite-size effects common in smaller simulations and reduces the flux to~5.5 × 1026 m−2 s−1, including ions that reflect back into the plasma—this flux is a factor of ~15 lower than is typically used in smaller simulations. These results indicate that prismatic loops with radii of ~3 nm that are centered 10 nm below the surface with Burgers vectors parallel to the surface cause helium atom clusters to accumulate at the edge of the dislocation core relatively quickly—within 100 to 150 ns of the onset of plasma exposure. Subsequent growth of these clusters, however, is relatively minimal even out to 1 μs or more. This is partially explained by the relatively high helium implantation flux, which causes bubbles to accumulate 0 to 7 nm below the surface and block the region of the metal containing the dislocation, but this is only part of the explanation. Another effect results from the strain field around the loop itself. The compressive regions along the direction of the Burgers vector repel helium, but the tensile region initially attracts helium and traps it. However, we believe that the attractive tensile stress region is effectively shielded by the formation of helium clusters on and above it, and these bubbles subsequently experience relatively slow growth.