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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.”
Wei Ji, William R. Martin
Nuclear Science and Engineering | Volume 169 | Number 1 | September 2011 | Pages 19-39
Technical Paper | doi.org/10.13182/NSE10-73
Articles are hosted by Taylor and Francis Online.
In this paper the chord method is applied to the computation of Dancoff factors for doubly heterogeneous stochastic media, characteristic of prismatic and pebble bed designs of the Very High Temperature Gas-Cooled Reactor (VHTR), where TRISO fuel particles are randomly distributed in fuel compacts or fuel pebbles that are arranged in a full core configuration. Previous work has shown that a chord length probability distribution function (PDF) can be determined analytically or empirically and used to model VHTR lattices with excellent results. The key observation is that once the chord length PDF is known, Dancoff factors for doubly heterogeneous stochastic media can be expressed as closed-form expressions that can be evaluated analytically for infinite and finite media and semianalytically for a collection of finite media.Based on the assumption that the chord length PDF in the moderator region between two fuel kernels in a VHTR compact or pebble is exponential, which was shown to be an excellent approximation in previous work, closed-form expressions for Dancoff factors are derived for a range of configurations from infinite stochastic media to finite stochastic media, including multiple finite stochastic media in a background medium (e.g., a pebble bed core). Numerical comparisons with Monte Carlo benchmark results demonstrate that the closed-form expressions for the Dancoff factors for VHTR configurations are accurate over a range of packing fractions characteristic of prismatic and pebble bed VHTRs.