Oklo is a region near the town of

Franceville Franceville is one of the four largest cities in Gabon, with a population of 110,568 at the 2013 census. It lies on the Mpassa River and at the end of the Trans-Gabon Railway and the N3 road. It grew from a village named Masuku when Pierre Savor ...

, in the Haut-Ogooué province of the

Central Africa Central Africa is a subregion of the African continent comprising various countries according to different definitions. Angola, Burundi, the Central African Republic, Chad, the Democratic Republic of the Congo, the Republic of the Congo, ...

n country of

Gabon Gabon (; ; snq, Ngabu), officially the Gabonese Republic (french: République gabonaise), is a country on the west coast of Central Africa. Located on the equator, it is bordered by Equatorial Guinea to the northwest, Cameroon to the north ...

. Several

natural nuclear fission reactor A natural nuclear fission reactor is a uranium deposit where self-sustaining nuclear chain reactions occur. The conditions under which a natural nuclear reactor could exist had been predicted in 1956 by Japanese American chemist Paul Kuroda. Th ...

s were discovered in the

uranium mines Uranium production is carried out in about 13 countries around the world, in 2017 producing a cumulative total of 59,462 tonnes of uranium (tU). The international producers were Kazakhstan (39%), Canada (22%), Australia (10%), Namibia (7.1%), Nig ...

in the region in 1972.

History

Gabon was a French colony when prospectors from the

French Alternative Energies and Atomic Energy Commission The French Alternative Energies and Atomic Energy Commission or CEA ( French: Commissariat à l'énergie atomique et aux énergies alternatives), is a French public government-funded research organisation in the areas of energy, defense and securit ...

(the industrial parts, which later became

Orano Cycle Orano Cycle, formerly COGEMA (''Compagnie générale des matières nucléaires'') and Areva NC, is a French nuclear company. It is the main subsidiary of Orano S.A. It is an industrial group active in all stages of the uranium fuel cycle, inclu ...

) discovered

uranium Uranium is a chemical element with the symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium is weak ...

in the remote region in 1956. France immediately opened mines operated by Comuf () near

Mounana Mounana is a town in Gabon. It lies on the N3 road and from 1958 until the 1990s was a major uranium mining centre. The mine is now closed, and it is now primarily a centre for agriculture Agriculture or farming is the practice of cultiva ...

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 Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

. Today the uranium deposits are exhausted, and the mine is no longer worked. Currently,

mine reclamation Mine reclamation is the process of modifying land that has been mined to ecologically functional or economically usable state. Although the process of mine reclamation occurs once mining is completed, the planning of mine reclamation activiti ...

work is ongoing in the region affected by the mine operations. Some of the mined uranium was found to have a lower concentration of

uranium-235 Uranium-235 (235U or U-235) is an isotope of uranium making up about 0.72% of natural uranium. Unlike the predominant isotope uranium-238, it is fissile, i.e., it can sustain a nuclear chain reaction. It is the only fissile isotope that exis ...

than expected, as if it had already been in a reactor. When geologists investigated they also found products typical of a reactor. They concluded that the deposit had been in a reactor: a

, around 1.8 to 1.7 billion years BP – in the Paleoproterozoic Era during

Precambrian The Precambrian (or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of the ...

times. At that time the natural uranium had a concentration of about 3% ²³⁵U, and could have reached criticality with natural water as

neutron moderator In nuclear engineering, a neutron moderator is a medium that reduces the speed of fast neutrons, ideally without capturing any, leaving them as thermal neutrons with only minimal (thermal) kinetic energy. These thermal neutrons are immensely mo ...

allowed by the special geometry of the deposit.

References

External links

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{{coord, 1, 23, 40, S, 13, 9, 39, E, type:mountain_region:GA_source:nlwiki, display=title Uranium mines Radioactive waste repositories Mines in Gabon Energy in Gabon Nuclear reactors

History

See also

References

External links