Report a Safety Concern

Search

The U.S. Nuclear Regulatory Commission is in the process of rescinding or revising guidance and policies posted on this webpage in accordance with Executive Order 14151 Ending Radical and Wasteful Government DEI Programs and Preferencing, and Executive Order 14168 Defending Women From Gender Ideology Extremism and Restoring Biological Truth to the Federal Government. In the interim, any previously issued diversity, equity, inclusion, or gender-related guidance on this webpage should be considered rescinded that is inconsistent with these Executive Orders.

Home NRC Library Basic References Glossary

Uranium

A radioactive element with the atomic number 92 and, as found in natural ores, an atomic weight of approximately 238. The two principal natural isotopes are uranium-235 (which comprises 0.7 percent of natural uranium), which is fissile, and uranium-238 (99.3 percent of natural uranium), which is fissionable by fast neutrons and is fertile, meaning that it becomes fissile after absorbing one neutron. Natural uranium also includes a minute amount of uranium-234.

Page Last Reviewed/Updated Friday, January 20, 2023