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.
Explore membership for yourself or for your organization.
Conference Spotlight
Nuclear Energy Conference & Expo (NECX)
September 8–11, 2025
Atlanta, GA|Atlanta Marriott Marquis
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
Aug 2025
Jan 2025
Latest Journal Issues
Nuclear Science and Engineering
September 2025
Nuclear Technology
Fusion Science and Technology
August 2025
Latest News
Powering the future: How the DOE is fueling nuclear fuel cycle research and development
As global interest in nuclear energy surges, the United States must remain at the forefront of research and development to ensure national energy security, advance nuclear technologies, and promote international cooperation on safety and nonproliferation. A crucial step in achieving this is analyzing how funding and resources are allocated to better understand how to direct future research and development. The Department of Energy has spearheaded this effort by funding hundreds of research projects across the country through the Nuclear Energy University Program (NEUP). This initiative has empowered dozens of universities to collaborate toward a nuclear-friendly future.
G. C. Pomraning
Nuclear Science and Engineering | Volume 127 | Number 2 | October 1997 | Pages 182-198
Technical Paper | doi.org/10.13182/NSE97-A28596
Articles are hosted by Taylor and Francis Online.
The problem of describing steady-state transport of a perpendicularly incident particle beam through a thin slab of material is considered. For a scattering kernel sufficiently peaked in momentum transfer to allow a Fokker-Planck description of the scattering process in both energy and angle, an approximate closed form solution to this problem was obtained almost 50 yr ago and is referred to as the Fermi-Eyges formula. It is shown that a Fermi-Eyges-like formula can be derived for a broader class of scattering kernels. This class consists of scattering described by the continuous slowing-down approximation (the Fokker-Planck description in energy), but not sufficiently forward peaked in angle to allow an angular Fokker-Planck representation. This generalized formula reduces to the classic Fermi-Eyges result for scattering operators with a valid Fokker-Planck limit and also describes problems that, while involving a forward-peaked scattering kernel, do not possess a Fokker-Planck description. A classic example of such a kernel is the Henyey-Greenstein kernel, and the Fermi-Eyges-like solution in this case exhibits more beam spreading than that predicted by the classic Fermi-Eyges formula. In particular, the scalar flux is non-Gaussian in the radial coordinate, as contrasted with the Gaussian Fermi-Eyges result.