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
Jul 2025
Jan 2025
Latest Journal Issues
Nuclear Science and Engineering
August 2025
Nuclear Technology
Fusion Science and Technology
Latest News
Sandia and Aeva evaluate intrusion detection system
Sandia National Laboratories is collaborating with the California-based Aeva Technologies, a developer of next-generation sensing and perception systems, on the development of technology for strengthening security at U.S. nuclear reactor sites.
Glen A. Mortensen and Harold P. Smith, Jr.
Nuclear Science and Engineering | Volume 22 | Number 3 | July 1965 | Pages 321-327
Technical Paper | doi.org/10.13182/NSE65-A20936
Articles are hosted by Taylor and Francis Online.
The time dependent P1 approximation to the neutron transport equation has been solved for the case of an oscillating source on one face of a finite parallelepiped. An oscillatory solution to the differential equations describes the propagation of neutron waves through the medium. Attenuation lengths of plane neutron waves were identical at low frequencies (ω < ½ νΣa) for the P1 and diffusion approximations but differ considerably at high frequencies (ω > 2ν Σtr). Wave lengths and wave speeds for the two approximations were slightly different at low frequencies, identical at immediate frequencies and considerably different at high frequencies. A new method, which considers the transient behavior of a spatially-integrated positive-definite function of flux and current, is used to show that the transient part of the solution decays to zero.