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
Aug 2025
Jan 2025
Latest Journal Issues
Nuclear Science and Engineering
September 2025
Nuclear Technology
August 2025
Fusion Science and Technology
Latest News
Chris Wagner: The role of Eden Radioisotopes in the future of nuclear medicine
Chris Wagner has more than 40 years of experience in nuclear medicine, beginning as a clinical practitioner before moving into leadership roles at companies like Mallinckrodt (now Curium) and Nordion. His knowledge of both the clinical and the manufacturing sides of nuclear medicine laid the groundwork for helping to found Eden Radioisotopes, a start-up venture that intends to make diagnostic and therapeutic raw material medical isotopes like molybdenum-99 and lutetium-177.
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.