natural radioactivity

https://doi.org/10.1351/goldbook.N04092
radioactivity of naturally occurring nuclides in materials where the isotopic abundance of that nuclides is natural.
Source:
PAC, 1982, 54, 1533. 'Glossary of terms used in nuclear analytical chemistry (Provisional)' on page 1546 (https://doi.org/10.1351/pac198254081533)