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
September 2025
Nuclear Technology
August 2025
Fusion Science and Technology
Latest News
Deep Space: The new frontier of radiation controls
In commercial nuclear power, there has always been a deliberate tension between the regulator and the utility owner. The regulator fundamentally exists to protect the worker, and the utility, to make a profit. It is a win-win balance.
From the U.S. nuclear industry has emerged a brilliantly successful occupational nuclear safety record—largely the result of an ALARA (as low as reasonably achievable) process that has driven exposure rates down to what only a decade ago would have been considered unthinkable. In the U.S. nuclear industry, the system has accomplished an excellent, nearly seamless process that succeeds to the benefit of both employee and utility owner.
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.
