Oklo natural reactors

https://doi.org/10.1351/goldbook.14892
Naturally occurring nuclear reactors arising through biogeochemical processes approximately 1.8 billion years ago in Oklo (Gabon, Africa).
Source:
PAC, 2009, 81, 829. (Glossary of terms used in ecotoxicology (IUPAC Recommendations 2009)) on page 922 [Terms] [Paper]