"Oklo" is the name of a region in Gabon with rich uranium deposits. In the 1970s, it was noticed that uranium mined from the region had a different isotopic makeup than expected, and it was characteristic of spent fuel.
Further investigation revealed that, billions of years (many half-lives) ago, when the naturally-occurring uranium was much "hotter", it was sufficiently concentrated to form a natural fission reactor. Groundwater acted as a moderator, and as the vein of ore would heat up from the reaction, the water would turn to steam, which would form voids in the moderator and slow the reaction down. It would cool, water would seep back in, and the reactor regulated itself this way for a few hundred thousand years before its fuel burned to a concentration too low to continue.
Now there's a startup with this name which is gonna make it harder to search for, but if that helps solve more problems than it creates, more power to them.
Imagine the alternate reality, very slightly different from ours, where nuclear reactors spontaneously erupted from the Earth's surface (in the modern anthropic era). Imagine a Pliny trying to make sense of a nuclear Vesuvius.
For anyone who missed HN's interesting feature yesterday: in the ancient Roman city of Hierapolis (modern Turkey), there is a lethal geological feature that emits invisible CO2. "But get an answer he did, almost immediately. "We saw dozens of dead creatures around the entrance: mice, sparrows, blackbirds, many beetles, wasps and other insects. So, we knew right away that the stories were true." And the Romans built a temple on top of this mysterious death -- and they called this temple the "Plutonium"!
Imagine the religious imagery if, instead of burning to death or suffocating in the ash, volcano eruption victims developed acute radiation sickness and stumbled into nearby villages puking their guts out and melting from the inside out.
It probably harmed some organisms, just not any organism that could complain about the adverse effects to us humans.
This thing happened 1.7 billion years ago, in Precambrian eon. So when this natural nuclear reactor was active there weren't many animals around anywhere in the world, let alone in that particular spot.
"Oklo" is the name of a region in Gabon with rich uranium deposits. In the 1970s, it was noticed that uranium mined from the region had a different isotopic makeup than expected, and it was characteristic of spent fuel.
Further investigation revealed that, billions of years (many half-lives) ago, when the naturally-occurring uranium was much "hotter", it was sufficiently concentrated to form a natural fission reactor. Groundwater acted as a moderator, and as the vein of ore would heat up from the reaction, the water would turn to steam, which would form voids in the moderator and slow the reaction down. It would cool, water would seep back in, and the reactor regulated itself this way for a few hundred thousand years before its fuel burned to a concentration too low to continue.
Now there's a startup with this name which is gonna make it harder to search for, but if that helps solve more problems than it creates, more power to them.