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
2025 ANS Winter Conference & Expo
November 8–12, 2025
Washington, DC|Washington Hilton
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
Oct 2025
Jul 2025
Latest Journal Issues
Nuclear Science and Engineering
December 2025
Nuclear Technology
November 2025
Fusion Science and Technology
Latest News
FPoliSolutions demonstrates RISE, an RIPB systems engineering tool
The American Nuclear Society’s Risk-informed, Performance-based Principles and Policy Committee (RP3C) has held another presentation in its monthly Community of Practice (CoP) series. Former RP3C chair N. Prasad Kadambi opened the October 3 meeting with brief introductory remarks about the RP3C and the need for new approaches to nuclear design that go beyond conventional and deterministic methods. He then welcomed this month’s speakers: Mike Mankosa, a project engineer at FPoliSolutions, and Cesare Frepoli, the company’s president, who together presented “Introduction to RISE: A Digital Framework for Maintaining a Risk-Informed Safety Case for Current and Next Generation Nuclear Power Plants.”
Watch the full webinar here.
Richard Sanchez
Nuclear Science and Engineering | Volume 177 | Number 1 | May 2014 | Pages 19-34
Technical Paper | doi.org/10.13182/NSE12-95
Articles are hosted by Taylor and Francis Online.
We investigate the degeneracy of the first-order PN equations and construct interface and boundary conditions that ensure a unique solution. Our technique is based on establishing an equivalence between the first- and second-order PN equations and showing that the (regular) second-order equations with opposite parity to N are nondegenerate. Assuming bounded angular flux moments and sources, we derive interface and boundary conditions for the regular second-order equations that, via the equivalence, are those to be used with the first-order PN equations. While providing independent derivations, our results reproduce those derived using solid harmonic expansions by Davison and Rumyantsev in the 1950s.
