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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.”
Gabriel Ghita, Glenn Sjoden, James Baciak
Nuclear Technology | Volume 168 | Number 3 | December 2009 | Pages 620-628
Neutron Measurements | Special Issue on the 11th International Conference on Radiation Shielding and the 15th Topical Meeting of the Radiation Protection and Shielding Division (PART 3) / Radiation Measurements and Instrumentation | doi.org/10.13182/NT09-A9279
Articles are hosted by Taylor and Francis Online.
We explore in this study the practical limits in designing a neutron detector array to resolve the spectra from special nuclear material (SNM) neutron sources using 3He detectors. We demonstrate that radiation transport analysis yielded a spectrum unfolding strategy based on the energy structure of the BUGLE-96 cross-section library, with 47 neutron energy groups. The initial computational model used is an isotropic planar source incident on a block of high-density polyethylene moderator. Assuming 3He is diluted throughout the moderator, the 3He(n,p) reaction rate energy group matrix in the block was computed using a completely "flat" neutron source spectrum. Analyzing the energy group matrix, there are neutrons from specific collections of energy groups (energy "bands") that induce a maximum reaction rate in specific locations; we determined that these groups cannot be further differentiated within the energy band using 3He detectors. It was determined that optimal spectral fidelity for SNM detection and characterization is achievable using four spectral bands spanning among groups 1 through 29 (31.8 keV to 17.3 MeV). Using ideal-filter materials to remove the neutrons from different regions of the spectrum, we predicted the maximum neutron spectral resolution obtainable using this approach. To demonstrate our method, we present the optimally detected spectral differences between SNM materials (plutonium and uranium), metal and oxide, using ideal-filter materials. We have also selected a number of candidate filtering materials and, by replacing the ideal filters with real materials, we exemplified our approach with a design of a neutron detector array capable of resolving the spectra from SNM neutron sources using 3He detectors.