A shekara ta 1972, masanin kimiyyar lissafi na Faransa Francis Perrin ya gano tsoffin tsoffin magungunan fission na halitta guda goma sha biyar da ba su da aiki a cikin ma'adinai uku daban-daban a cikin ma'adinan Oklo a Gabon, Afirka ta Yamma, wanda aka sani da suna Oklo Fossil Reactors. Ma'adinan ma'adinan yana da shekaru biliyan 1.7; to, uranium-235 ya kasance kusan kashi 3% na jimlar uranium a duniya. Wannan ya isa ya ba da damar ci gaba da jerin gwano na fission na nukiliya, idan akwai wasu yanayin tallafi.
Shekaru biliyan 1.7