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
Operations & Power
Members focus on the dissemination of knowledge and information in the area of power reactors with particular application to the production of electric power and process heat. The division sponsors meetings on the coverage of applied nuclear science and engineering as related to power plants, non-power reactors, and other nuclear facilities. It encourages and assists with the dissemination of knowledge pertinent to the safe and efficient operation of nuclear facilities through professional staff development, information exchange, and supporting the generation of viable solutions to current issues.
Meeting Spotlight
International Conference on Mathematics and Computational Methods Applied to Nuclear Science and Engineering (M&C 2025)
April 27–30, 2025
Denver, CO|The Westin Denver Downtown
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
Apr 2025
Jan 2025
Latest Journal Issues
Nuclear Science and Engineering
May 2025
Nuclear Technology
Fusion Science and Technology
Latest News
TerraPower begins U.K. regulatory approval process
Seattle-based TerraPower signaled its interest this week in building its Natrium small modular reactor in the United Kingdom, the company announced.
TerraPower sent a letter to the U.K.’s Department for Energy Security and Net Zero, formally establishing its intention to enter the U.K. generic design assessment (GDA) process. This is TerraPower’s first step in deployment of its Natrium technology—a 345-MW sodium fast reactor coupled with a molten salt energy storage unit—on the international stage.
I. Pázsit, Y. Yamane
Nuclear Science and Engineering | Volume 133 | Number 3 | November 1999 | Pages 269-281
Technical Paper | doi.org/10.13182/NSE99-A2087
Articles are hosted by Taylor and Francis Online.
The Feynman- and Rossi-alpha formulas are calculated for subcritical systems driven by a multiple emission source, i.e., one that emits several neutrons on each source emission event. The prime example of such sources is a spallation source, which will be used in future accelerator-driven subcritical systems (ADS), such as the energy amplifier. The Feynman- and Rossi-alpha formulas are calculated with backward master equations for such systems. The essence of the theory is a formula that connects the probability distribution of a cascade, induced by one single particle, with that induced by a continuous source of particles. Compact and consistent expressions are found for both the Feynman- and Rossi-alpha formulas. In agreement with earlier forward-theory-based or heuristic calculations, it is shown that the presence of the spallation source does not alter the time-dependence of the formulas, but enhances its amplitude. Hence, both methods appear to be promising to be used in future stationary ADS systems with relatively large subcriticalities.
