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
2026 Nuclear Energy Conference & Expo (NECX)
August 24–27, 2026
Dallas, TX|Hilton Anatole
Latest Magazine Issues
Jul 2026
Jan 2026
2026
Latest Journal Issues
Nuclear Science and Engineering
August 2026
Nuclear Technology
July 2026
Fusion Science and Technology
Latest News
The deadline arrives: Checking in on the Reactor Pilot Program
On May 23, 2025, President Trump signed Executive Order 14301, “Reforming Nuclear Reactor Testing at the DOE,” which instructed the Department of Energy to create a Reactor Pilot Program (RPP)—a new system in which companies could pursue DOE authorization to build and test their first-of-a-kind nuclear technologies. EO 14301 set an ambitious goal for that program: three reactors achieving criticality by July 4, 2026.
E. Richard Cohen
Nuclear Science and Engineering | Volume 89 | Number 1 | January 1985 | Pages 99-102
Technical Note | doi.org/10.13182/NSE85-A17887
Articles are hosted by Taylor and Francis Online.
The process of neutron slowing down in a nonabsorbing medium is reviewed, and the distinction between average energy or lethargy after n collisions and the average number of collisions to reach a given energy is emphasized. Fermi's remark about neutron slowing down in hydrogen is explained and rederived.
