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
Nuclear Criticality Safety
NCSD provides communication among nuclear criticality safety professionals through the development of standards, the evolution of training methods and materials, the presentation of technical data and procedures, and the creation of specialty publications. In these ways, the division furthers the exchange of technical information on nuclear criticality safety with the ultimate goal of promoting the safe handling of fissionable materials outside reactors.
Meeting Spotlight
2024 ANS Winter Conference and Expo
November 17–21, 2024
Orlando, FL|Renaissance Orlando at SeaWorld
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 2024
Jan 2024
Latest Journal Issues
Nuclear Science and Engineering
October 2024
Nuclear Technology
Fusion Science and Technology
August 2024
Latest News
New laws offer nuclear industry incentives for existing power plant uprates
This year, the U.S. nuclear industry received a much-needed economic boost that could help preserve operating nuclear power plants and incentivize upgrades that extend their lifespan and power output.
Signed into law in 2022, the Inflation Reduction Act offers production tax credits (PTCs) for existing nuclear power plants and either PTCs or investment tax credits (ITCs) for new carbon-free generation. These credits could make power uprates—increasing the maximum power level at which a commercial plant may operate—a much more appealing option for utilities.
G. C. Pomraning
Nuclear Science and Engineering | Volume 108 | Number 4 | August 1991 | Pages 325-330
Technical Paper | doi.org/10.13182/NSE91-A23831
Articles are hosted by Taylor and Francis Online.
Within the context of one-group diffusion theory, we discuss the effect of randomness (stochasticity) on the criticality of a bare nuclear reactor. Previous authors have concluded that randomness decreases the critical size for a given amount of fuel, and that such randomness, when in-troduced into a homogeneous critical reactor, leads most probably to a supercritical state. By considering a sufficiently simple stochastic problem so that exact results can be obtained, we judge these prior conclusions to be only partially correct. We show that the effect of randomness on a criticality problem depends on both the nature of the randomness and the ensemble-averaging procedure and interpretation used to describe the reactor in the stochastic setting.