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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.”
Jin-Li Cao, Wei Xiao, Qi Cao, Bing-Ling He
Fusion Science and Technology | Volume 74 | Number 3 | October 2018 | Pages 177-185
Technical Paper | doi.org/10.1080/15361055.2017.1416245
Articles are hosted by Taylor and Francis Online.
Experiments observed preferential He bubble formation in carbide precipitates M23C6 during low-temperature He irradiation in ferritic-martensitic steels. However, the process and mechanism of He trapping in M23C6 present a challenge to measure. Using density functional theory, we have systematically investigated He distribution, migration, and accumulation in Cr23C6. The formation energies of interstitial and substitutional He in Cr23C6 are 3.50 and 3.16 eV, respectively, remarkably lower than those in Fe matrix. The higher solubility of He in Cr23C6 makes it an He-trapping center in martensitic steels. On the other hand, the migration barrier of interstitial He in Cr23C6 is 2.58 eV, about 2.52 eV higher than that in bulk Fe. Furthermore, we only find a very weak attraction potency for substitutional-interstitial He pair, 0.25 eV, and even no binding trend for interstitial-interstitial or substitutional-substitutional He pairs, which suggests that it is more difficult for He atoms to move and less powerful driving force to accumulate in Cr23C6 than those in Fe matrix. Our results indicate that the trapping effect results from a lower charge density zone in Cr23C6, and predict that the small and dense Cr23C6 particles may hinder bubble growth at the initial stage, which can improve the resistance to irradiation void swelling.
