Oklo

Oklo is a region near Franceville in the Haut-Ogooué Province of Gabon. Several natural nuclear fission reactors were discovered in the uranium mines in the region in 1972.

Natural nuclear fission reactor

Some of the mined uranium was found to have a lower concentration of uranium-235 than expected, as if it had already been in a nuclear reactor. When geologists investigated they also found products typical of a reactor. They concluded that the deposit had been in a reactor: a natural nuclear fission reactor, around 1.8 to 1.7 billion years BP – in the Paleoproterozoic Era during Precambrian times, during the Statherian period – and continued for a few hundred thousand years, probably averaging less than 100 kW of thermal power during that time. At that time the natural uranium had a concentration of about 3% ²³⁵U and could have reached criticality with natural water as neutron moderator allowed by the special geometry of the deposit.<ref>Template:Cite book</ref><ref>Template:Cite book</ref><ref name="tz">Template:Cite book</ref><ref>Template:Cite magazine</ref><ref>Template:Cite web</ref><ref>Template:Cite journal</ref><ref>Template:Cite magazine</ref>