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
July 2025
Latest News
DOE issues new NEPA rule and procedures—and accelerates DOME reactor testing
Meeting a deadline set in President Trump’s May 23 executive order “Reforming Nuclear Reactor Testing at the Department of Energy,” the DOE on June 30 updated information on its National Environmental Policy Act (NEPA) rulemaking and implementation procedures and published on its website an interim final rule that rescinds existing regulations alongside new implementing procedures.
Yung-An Chao, Anthony Attard
Nuclear Science and Engineering | Volume 90 | Number 1 | May 1985 | Pages 40-46
Technical Paper | doi.org/10.13182/NSE85-A17429
Articles are hosted by Taylor and Francis Online.
The stiffness problem in reactor kinetics is overcome by the stiffness confinement method for solving the kinetic equations. The idea is based on the observation that the stiffness characteristic is present only in the time response of the prompt neutron density, but not in that of the delayed neutron precursors. The method is, therefore, devised to have the stiffness decoupled from the differential equations for precursors and confined to the one for the prompt neutrons, which can be analytically solved. Numerical examples of applying the method to a variety of problems confirm that the time step increment size can be greatly increased and that much computing time can be saved, as compared to other conventional methods. The theory is of general validity and involves no approximation other than the discretization of the time variable.