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Reactor Physics
The division's objectives are to promote the advancement of knowledge and understanding of the fundamental physical phenomena characterizing nuclear reactors and other nuclear systems. The division encourages research and disseminates information through meetings and publications. Areas of technical interest include nuclear data, particle interactions and transport, reactor and nuclear systems analysis, methods, design, validation and operating experience and standards. The Wigner Award heads the awards program.
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ANS Student Conference 2025
April 3–5, 2025
Albuquerque, NM|The University of New Mexico
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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.”
Uncheol Shin, Warren F. Miller, Jr.
Nuclear Science and Engineering | Volume 128 | Number 1 | January 1998 | Pages 27-46
Technical Paper | doi.org/10.13182/NSE98-A1943
Articles are hosted by Taylor and Francis Online.
Using an asymptotic expansion, we found that the modified time-dependent simplified P2 (SP2) equations are robust, high-order, asymptotic approximations to the time-dependent transport equation in a physical regime in which the conventional time-dependent diffusion equation is the leading-order approximation. Using diffusion limit analysis, we also asymptotically compared three competitive time-dependent equations (the telegrapher's equation, the time-dependent SP2 equations, and the time-dependent simplified even-parity equation). As a result, we found that the time-dependent SP2 equations contain higher-order asymptotic approximations to the time-dependent transport equation than the other competitive equations. The numerical results confirm that, in the vast majority of cases, the time-dependent SP2 solutions are significantly more accurate than the time-dependent diffusion and the telegrapher's solutions. We have also shown that the time-dependent SP2 equations have excellent characteristics such as rotational invariance (which means no ray effect), good diffusion limit behavior, guaranteed positivity in diffusive regimes, and significant accuracy, even in deep-penetration problems. Through computer-running-time tests, we have shown that the time-dependent SP2 equations can be solved with significantly less computational effort than the conventionally used, time-dependent SN equations (for N > 2) and almost as fast as the time-dependent diffusion equation. From all these results, we conclude that the time-dependent SP2 equations should be considered as an important competitor for an improved approximate transport equation solver. Such computationally efficient time-dependent transport models are especially important for problems requiring enhanced computational efficiency, such as neutronics/fluid-dynamics coupled problems that arise in the analyses of hypothetical nuclear reactor accidents.
