Around this time, a natural nuclear fission reactor was active in what is now Gabon, West Africa. Unique geological conditions allowed a self-sustaining chain reaction to occur in uranium-rich rock formations, without human intervention.
# Metadata
Title: Oklo Nuclear Reactor Active Movietime: 5:47 Geographical Time: 2000 Ma
Around 2 billion years ago, a remarkable natural phenomenon occurred in what is now Gabon, Africa. Under specific geological conditions, the uranium-rich deposits at Oklo reached a critical mass and sustained nuclear fission reactions — forming the only known naturally occurring nuclear reactors on Earth. At that time, the ratio of uranium-235 to uranium-238 was much higher than today, approximately 3%, enabling fission without artificial enrichment. Groundwater percolating through the rock served as a neutron moderator, allowing controlled chain reactions to persist for hundreds of thousands of years. Once the water boiled away, the reaction would stop, only to resume when groundwater returned — a self-regulating process. These reactors are estimated to have generated up to 100 kilowatts of power, operating intermittently over a span of several thousand years. The discovery of Oklo in the 1970s offered unique insight into nuclear physics, geochemistry, and the long-term stability of nuclear waste storage in geological formations.