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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.”
Tetsuya Suzuki, Toyohiko Yano, Tsutomu Mori, Hiroyuki Miyazaki, Takayoshi Iseki
Fusion Science and Technology | Volume 27 | Number 3 | May 1995 | Pages 314-325
Technical Paper | Materials Engineering | doi.org/10.13182/FST95-A30393
Articles are hosted by Taylor and Francis Online.
Neutron irradiation uniformly produces vacancies and interstitials in silcon carbide (SiC) poly crystals, and the specimen swells by 1 to 3%. Subsequent isochronal annealing leads to annihilation of the defects by the interstitial-vacancy recombination from around irradiation temperature, resulting in the shrinkage of the specimen. This shrinkage can be detected by measuring the specimen length with a conventional micrometer and its lattice parameter with an X-ray diffractometer. Furthermore, defect formation and annihilation affect the electrical resistivity and create paramagnetic centers caused by unpaired electrons. Helium atoms can be uniformly introduced into SiC utilizing the nuclear reaction of 10B(n, α)7 Li. By subsequent annealing above ∼1300°C, helium atoms with high vibration energy capture thermal vacancies to reduce the internal pressure and form bubbles at grain boundaries. The formation of helium bubbles accompanies a large volume expansion with increasing temperature, controlled by Greenwood et al.'s mechanism. The presence of helium bubbles at the grain boundaries promotes diffusional creep at lower temperatures (1300°C). Changes in physical properties by neutron irradiation are presented and discussed with respect to microstructures.