United States Nuclear Regulatory Commission - Protecting People and the Environment
Home > NRC Library > Basic References > Glossary > Fast fission

Fast fission

Fission of a "heavy" atom (such as uranium-238) when it absorbs a fast (high energy) neutron. All fissionable materials can fission with fast neutrons. However, some (such as uranium-235 and Plutonium-239) fission more readily with slow (thermal) neutrons.

Page Last Reviewed/Updated Tuesday, April 26, 2016