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
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.
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
Mar 2025
Jul 2024
Latest Journal Issues
Nuclear Science and Engineering
March 2025
Nuclear Technology
Fusion Science and Technology
February 2025
Latest News
ANS 2025 election is open
The American Nuclear Society election is now open. Members can vote for the Society’s next vice president/president-elect and treasurer as well as six board members (four U.S. directors, one non-U.S. director, and one student director). Completed ballots must be submitted by 1:00 p.m. (EDT) on Tuesday, April 15, 2025.
R. A. Rydin, J. A. Burke, W. E. Moore, K. W. Seemann
Nuclear Science and Engineering | Volume 46 | Number 2 | November 1971 | Pages 179-196
Technical Paper | doi.org/10.13182/NSE71-A22352
Articles are hosted by Taylor and Francis Online.
A series of space-time reactor kinetics experiments has been performed in the Solid Homogeneous Assembly. The ground rules were the following: 1. The cores were to be easy to model statically using few-group diffusion theory. 2. The dynamic behavior was to be one dimensional. 3. Significant flux tilt and delayed neutron flux tilt holdback effects were to be present. 4. The perturbation was to be essentially a negative step change in reactivity. 5. The flux distributions, absorber worths, and eigenvalue separation of each core were to be measurable in order to use this information to verify the core modeling process. The adequacy of few-group diffusion theory was checked using both one-dimen-sional multigroup (fast and thermal) and two-dimensional few-group transport theory calculations. The few-group diffusion theory model was solved in a cylindrical approximation using a finite difference code, and in correct 3D geometry using a synthesis code; the latter did an excellent job of predicting criticality and matching foil activation traverses made using the 55Mn (n, γ) thermal and 115In (n, n’) threshold reactions. The eigenvalue separation of each core was measured using both a static flux tilt method and a two-detector noise correlation method; the results agreed well with calculated values, indicating that these new experimental methods can provide an accurate determination of the eigenvalue separation of a core. The transient response of one of the cores to a step perturbation was compared to the response calculated using the space-time synthesis model. In general, it has been found that the transient response of the core can be predicted accurately provided that the core is well modeled statically, including the perturbation worth and the eigenvalue separation, and provided that the effective delayed neutron fraction is properly evaluated. This tends to verify the adequacy of existing methods for computing spatially dependent transients in cores describable by few-group diffusion theory.