Gabon was a French colony when prospectors from the
French Alternative Energies and Atomic Energy Commission (the industrial parts, which later became
Orano Cycle) discovered
uranium in the remote region in 1956. France immediately opened mines operated by Comuf (Compagnie des Mines d'Uranium de Franceville) near
Mounana village to exploit the vast mineral resources, and the state of Gabon was given a minority share in the company.
For 40 years, France mined uranium in Gabon. Once extracted, the uranium was used for electricity production in France and much of Europe. Today the uranium deposits are exhausted, and the mine is no longer active. Currently,
mine reclamation work is ongoing in the region affected by the mine operations.
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.[1][2][3][4][5][6][7]
^Cowan, George (1976).
"Oklo – A Natural Fission Reactor"(PDF). Federation of American Scientists. Los Alamos Scientific Laboratory.
Archived(PDF) from the original on 29 March 2024. Retrieved 15 August 2023.