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.
Edward W. Larsen, J. E. Morel, John M. McGhee
Nuclear Science and Engineering | Volume 123 | Number 3 | July 1996 | Pages 328-342
Technical Paper | doi.org/10.13182/NSE123-328
Articles are hosted by Taylor and Francis Online.
The multigroup P1 and simplified PN (SPN) equations are derived by an asymptotic expansion of the multigroup transport equation with anisotropic scattering. The P1 equations are the leading-order approximation in this expansion; the SPN equations for N = 2,3,… are increasingly higher order approximations. The physical assumptions underlying these approximations are that the material system is optically thick, the probability of absorption is small, and the mean scattering angle is not close to unity. For multigroup isotropic scattering transport problems, a dispersion analysis is given that verifies the accuracy of the SPN approximations. Numerical comparisons of P1, SPN, and SN solutions are also given. These comparisons show that for low N, SPN solutions are significantly more accurate (transportlike) than P1 solutions and are obtained at a significantly lower computational cost than SN solutions.
