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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.”
Abhishek Chakraborty, Suneet Singh, M. P. S. Fernando
Nuclear Science and Engineering | Volume 196 | Number 6 | June 2022 | Pages 715-734
Technical Paper | doi.org/10.1080/00295639.2021.2011670
Articles are hosted by Taylor and Francis Online.
Large nuclear reactors operating in the thermal spectrum are prone to both global and regional oscillations in power due to variation of 135Xe concentration. These power oscillations are self-stabilizing up to a certain operating power level, beyond which spatial power control becomes necessary for suppressing these oscillations. Especially for large pressurized heavy water reactors (PHWRs), which are natural uranium–fueled reactors using heavy water as coolant and moderator, the modes of xenon instabilities decide the extent and scheme for spatial power control. In this paper, the effect of spatial control on the bifurcation characteristics is demonstrated using a two-region model. The error signal for movement of the reactivity device has a global component for bulk power control and a local component for regional power control. The amount of regional power control determines the power level at which the spatial xenon oscillations stabilize. Using bifurcation analysis, it is found that in case of limited regional control, both supercritical and subcritical Hopf bifurcations exist, whereas in the case of increased regional control only supercritical Hopf bifurcations exist. However, these supercritical Hopf oscillations are due to time lag in control and have short timescales and lower amplitudes as compared to xenon oscillations. Hence, a proper choice of spatial control enables a PHWR to operate at rated full power capacity without any spatial Xenon instability.
