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.
Division Spotlight
Reactor Physics
The division's objectives are to promote the advancement of knowledge and understanding of the fundamental physical phenomena characterizing nuclear reactors and other nuclear systems. The division encourages research and disseminates information through meetings and publications. Areas of technical interest include nuclear data, particle interactions and transport, reactor and nuclear systems analysis, methods, design, validation and operating experience and standards. The Wigner Award heads the awards program.
Meeting Spotlight
2024 ANS Annual Conference
June 16–19, 2024
Las Vegas, NV|Mandalay Bay Resort and Casino
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
May 2024
Jan 2024
Latest Journal Issues
Nuclear Science and Engineering
June 2024
Nuclear Technology
Fusion Science and Technology
Latest News
Proving DRACO will deliver
The United States is now closer than it has been in over five decades to launching the first nuclear thermal rocket into space, thanks to DRACO—the Demonstration Rocket for Agile Cislunar Orbit.
C. J. Hah, T. J. Downar
Nuclear Science and Engineering | Volume 121 | Number 3 | December 1995 | Pages 405-415
Technical Paper | doi.org/10.13182/NSE95-A24143
Articles are hosted by Taylor and Francis Online.
The application of nodal equivalence theory (NET) in multigroup diffusion theory has required the use of “discontinuity factors” (DFs) to account for the homogenization errors that are inherent in all coarse-mesh nodal methods. Traditionally, DFs have been applied directly to the nodal matrix equations as multipliers to the group constants. For most problems of practical interest, the application of DFs has not led to the divergence of the iterative methods used to solve the discretized nodal equations. However, because of the large discontinuity factors resulting from the steep flux gradients in the modular high-temperature gas reactor, the inner and upscatter iterations failed to converge, motivating an investigation into alternative methods for applying NET. In this work, the augmented source method (ASM) for applying NET to the nodal expansion method is introduced. External surface sources at a node boundary are introduced to account for the homogenization errors thereby preserving the original matrix properties for which convergence of iterative methods is guaranteed. The ASM produced converged solutions for any magnitude of DFs and reproduced the reference solution when the augmented sources were constructed from the reference quantities. The application of the ASM to the core depletion calculation demonstrated the use of various approximations for the augmented source. An augmented source, which was constant during the burnup cycle, resulted in an improved solution in which the eigenvalue error was reduced by a factor of 6 compared with the nodal solution without DFs.