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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.”
Yeon Sang Jung, Won Sik Yang
Nuclear Science and Engineering | Volume 185 | Number 2 | February 2017 | Pages 307-324
Technical Paper | doi.org/10.1080/00295639.2016.1272369
Articles are hosted by Taylor and Francis Online.
This paper presents the method and performance of a coarse-mesh finite difference (CMFD) scheme for accelerating neutron transport calculations based on the finite element method (FEM). The transport solution based on FEM does not satisfy the neutron balance exactly because FEM yields a nonconservative discretization. A modified CMFD formulation has been developed to correct the limitation of the conventional CMFD that is applicable only to neutronics solvers with a conservative discretization. A consistent CMFD problem for the transport solution based on FEM is constructed by enforcing the neutron balance in each coarse mesh by introducing a pseudo absorption cross section, and the well-established alternating solution process of CMFD and transport calculations is employed to accelerate source convergence. The applicability of the modified CMFD scheme to transport calculation based on FEM was first tested for a one-dimensional, discrete ordinates (SN), discontinuous FEM. The performance of CMFD acceleration was then investigated with a two-dimensional/three-dimensional method of characteristic transport solver for thermal and fast reactor problems with various core sizes. It was observed that the consistent CMFD scheme could improve the computational efficiency of eigenvalue calculation significantly in the framework of a transport solver with fission source iteration.