Open main menu


The property of an unstable atomic nucleus losing energy by emitting radiation (radioactive decay). Radioactivity also refers to the expectation value of the number of radioactive decays occurring in a given quantity of material per unit time. The SI unit of radioactivity is per second (s-1) and its special name is becquerel (Bq). Also called activity.

ICRP Glossary entry - June 2019

Return to Glossary