For the benefit of the unfamiliar, there is only one natural fission reactor that has been found on earth. https://www.iaea.org/newscenter/news/meet-oklo-the-e

For the benefit of the unfamiliar, there is only one natural fission reactor that has been found on earth. https://www.iaea.org/newscenter/news/meet-oklo-the-earths-two-billion-year-old-only-known-natural-nuclear-reactor https://www.iaea.org/newscenter/news/meet-oklo-the-earths-tw...