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
Conference on Nuclear Training and Education: A Biennial International Forum (CONTE 2025)
February 3–6, 2025
Amelia Island, FL|Omni Amelia Island Resort
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
Jan 2025
Jul 2024
Latest Journal Issues
Nuclear Science and Engineering
February 2025
Nuclear Technology
Fusion Science and Technology
Latest News
IEA report: Challenges need to be resolved to support global nuclear energy growth
The International Energy Agency published a new report this month outlining how continued innovation, government support, and new business models can unleash nuclear power expansion worldwide.
The Path to a New Era for Nuclear Energy report “reviews the status of nuclear energy around the world and explores risks related to policies, construction, and financing.”
Find the full report at IEA.org.
D. C. Leslie, A. Jonsson
Nuclear Science and Engineering | Volume 23 | Number 1 | September 1965 | Pages 82-89
Technical Paper | doi.org/10.13182/NSE65-A19261
Articles are hosted by Taylor and Francis Online.
In a previous paper Leslie, Hill and Jonsson put forward a method for the rapid evaluation of the Dancoff factor in regular arrays of fuel rods. They also showed how extended rational approximations to the fuel nonescape probability could be used to improve the form of the equivalence theorem based on Wigner's rational approximation. This form of equivalence asserts that the resonance integral is a function of the geometry through the excess potential scattering 1/N only, where N is the number density of the absorber and is the mean chord. In the modification proposed by Leslie, Hill and Jonsson, this function is generalized to a/N; the Bell factor a is found to vary with coolant density. By making use of an approximate analytic method for the calculation of collision probabilities in geometries more general than regular arrays, the present authors extend this work to cluster-type fuel elements. The basic procedure is the same as in the work referred to above. An analytic expression for the fuel-to-fuel collision probability is derived using arguments about its behavior in the black and white limits (i.e. in the limits of high and low cross sections). The Dancoff factor is derived from the behavior in the black limit. It is shown, by comparison with exact calculations, that for two types of cluster geometry of current interest in fuel element design, the proposed Dancoff factor is in error by at most 2%. Improved equivalence relations for cluster geometry are also considered. It has been customary to assume that the cluster is equivalent to an isolated rod of diameter dp/Γ, where dp is the diameter of a single pin in the cluster and Γ is the Dancoff factor. Such a procedure implies that the Bell factor of the cluster is constant and equal to its value for an isolated rod. It is shown in this paper that the Bell factor is a function of coolant density and that, in a particular case, the cluster is almost equivalent to an isolated rod at low density. As the density increases, the Bell factor drops rapidly by 6% and then increases slowly.
