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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.”
F. J. Homan, T. B. Lindemer, E. L. Long, Jr., T. N. Tiegs, R. L. Beatty
Nuclear Technology | Volume 35 | Number 2 | September 1977 | Pages 428-441
Performance and Performance Modeling | Coated Particle Fuel / Fuel | doi.org/10.13182/NT35-428
Articles are hosted by Taylor and Francis Online.
Two fuel failure mechanisms were identified for coated particle fuels that are directly related to fuel kernel stoichiometry. These mechanisms are thermal migration of the kernel through the coating layers and chemical interaction between rare-earth fission products and the silicon carbide (SiC) layer (the primary barrier to diffusion of metal fission products out of the particle) leading to failure of the SiC layer. Thermal migration appears to be most severe for oxide fuels, while chemical interaction is most severe with carbide systems. Thermodynamic calculations indicated that oxide-carbide fuel kernels may permit a stoichiometry that reduces both problems to manageable levels for currently planned high-temperature gas-cooled reactors. Such stoichiometry adjustment is possible over the complete spectrum from UO2 to UO2 for the present recycle fuel, a weak acid resin (WAR)-derived fissile kernel. Thermodynamic calculations indicate that WAR kernels containing <15% UC2 (>85% UO2) will develop excessive CO overpressures within the particle during irradiation. In 100% UO2 particles, thermal migration and oxidation of the SiC layer were observed after irradiation. The calculations also indicate that WAR kernels containing >70% UC2 (<30% UC2) contain insufficient oxygen to oxidize the rare-earth fission products formed in fuel operated to the maximum burnup levels of 75% fissions per initial metal atom (75% FIMA). Instead, the rare earths are present in part or completely as dicarbides. As such, they were observed to segregate from the kernel and collect at the SiC interface on the cold side of the particle, react with the SiC, and eventually fail this coating. Five WAR kernel stoichiometries were irradiated. These are either UO2 kernels, UO2 plus 15, 50, or 75% UC2, or 100% UC2. Results of these tests are consistent with thermodynamic calculations. Additional tests are in progress to establish the optimum stoichiometry; preliminary indications suggest an optimum value of ∼35% conversion with a permissible range of ±20%.
