Gabon
Sand Origin
Libreville
Random Sand Fact
In Gabon, a nuclear reactor started by itself almost two billion years ago. The fuel lay in sandstone.
In 1972, French scientists examined uranium from Oklo. Something was wrong. The uranium looked as if it had already been used as nuclear fuel, even though it came straight from a mine.
The explanation lay far back in time. Natural nuclear reactors had started up in the rock, long before there were any humans.
At Oklo, uranium had collected in sandstone formed from sand once laid down in a river delta. Between the grains were tiny spaces where groundwater could seep in and reach the uranium.
The water slowed the neutrons released as the uranium split, making it easier for them to split more uranium and keep the reaction going.
When the heat made the water boil away, the reaction stopped. The rock cooled, fresh water seeped in, and the reactor started again. It is thought to have run for hundreds of thousands of years.
