Nature’s Own Nuclear Reactor.

From the website:

Creating a nuclear reaction is not simple. In power plants, it involves splitting uranium atoms, and that process releases energy as heat and neutrons that go on to cause other atoms to split. This splitting process is called nuclear fission. In a power plant, sustaining the process of splitting atoms requires the involvement of many scientists and technicians.

It came as a great surprise to most, therefore, when, in 1972, French physicist Francis Perrin declared that nature had beaten humans to the punch by creating the world’s first nuclear reactors. Indeed, he argued, nature had a two-billion-year head start.1 Fifteen natural fission reactors have been found in three different ore deposits at the Oklo mine in Gabon, West Africa. These are collectively known as the Oklo Fossil Reactors.

Here’s the story: Link - Thanks Daniel Kim!