ANS is committed to advancing, fostering, and promoting the development and application of nuclear sciences and technologies to benefit society.
Explore the many uses for nuclear science and its impact on energy, the environment, healthcare, food, and more.
Division Spotlight
Nuclear Criticality Safety
NCSD provides communication among nuclear criticality safety professionals through the development of standards, the evolution of training methods and materials, the presentation of technical data and procedures, and the creation of specialty publications. In these ways, the division furthers the exchange of technical information on nuclear criticality safety with the ultimate goal of promoting the safe handling of fissionable materials outside reactors.
Meeting Spotlight
ANS Student Conference 2025
April 3–5, 2025
Albuquerque, NM|The University of New Mexico
Standards Program
The Standards Committee is responsible for the development and maintenance of voluntary consensus standards that address the design, analysis, and operation of components, systems, and facilities related to the application of nuclear science and technology. Find out What’s New, check out the Standards Store, or Get Involved today!
Latest Magazine Issues
Apr 2025
Jan 2025
Latest Journal Issues
Nuclear Science and Engineering
May 2025
Nuclear Technology
April 2025
Fusion Science and Technology
Latest News
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.”
W. B. Doub
Nuclear Science and Engineering | Volume 10 | Number 4 | August 1961 | Pages 299-307
doi.org/10.13182/NSE61-A15371
Articles are hosted by Taylor and Francis Online.
An approximate heuristic expression for the particle self-shielding factor for a set of purely absorbing spheres of radius r and volume fraction V well mixed with another set of non-absorbing spheres has been derived. The resulting expression has been experimentally verified using transmission data at several incident neutron energies for a plate-type sample containing a mixture of aluminum and boron-carbide spheres with nominal diameters 85 ± 15µ. The boron-carbide spheres occupied about 37% of the sample volume. The transmission was measured at energies ranging from 0.03 to 1.2 ev using a crystal neutron spectrometer. Since, however, the sample contained boron-carbide spheres with a distribution of diameters, the experimental self-shielding factors are “average” values. It is shown, using an approximate model, that a plausible theoretical self-shielding factor is a volume weighted average of the self-shielding factors for the spheres of diameters, d1, d2, d3, … . The particle self-shielding factors derived by several other authors have also been compared with the present experimental results. The Hurwitz-Zweifel expression (1) gives quite bad agreement, though this is expected because of the high volume fraction of poison in the sample. The Burrus expression (2, 3) gives much better agreement though not as good as the expression derived in this paper.