Oklo
Encyclopedia
Oklo is a region near the town of Franceville
Franceville
Franceville or Masuku is one of the four largest cities in Gabon, with a population of around 22,000 people. It lies on the River Mpassa and at the end of the Trans-Gabon Railway and the N3 road. It grew from a village named Masuku when Pierre Savorgnan de Brazza chose it to resettle former...
, in the Haut-Ogooué
Haut-Ogooué
Haut-Ogooué is one of Gabon's nine provinces. It is named after the Ogooué River. It covers an area of 36,547 km². The provincial capital is Franceville. One of its primary industries is mining, with manganese, gold and uranium being found in the region. The uranium-bearing mineral Francevillite...
province of the Central Africa
Central Africa
Central Africa is a core region of the African continent which includes Burundi, the Central African Republic, Chad, the Democratic Republic of the Congo, and Rwanda....
n state of Gabon
Gabon
Gabon , officially the Gabonese Republic is a state in west central Africa sharing borders with Equatorial Guinea to the northwest, Cameroon to the north, and with the Republic of the Congo curving around the east and south. The Gulf of Guinea, an arm of the Atlantic Ocean is to the west...
. Several natural nuclear fission reactor
Natural nuclear fission reactor
A natural nuclear fission reactor is a uranium deposit where analysis of isotope ratios has shown that self-sustaining nuclear chain reactions have occurred. The existence of this phenomenon was discovered in 1972 at Oklo in Gabon, Africa, by French physicist Francis Perrin. The conditions under...
s were discovered in the uranium mines
Uranium mining
Uranium mining is the process of extraction of uranium ore from the ground. The worldwide production of uranium in 2009 amounted to 50,572 tonnes, of which 27% was mined in Kazakhstan. Kazakhstan, Canada, and Australia are the top three producers and together account for 63% of world uranium...
in the region in 1972.
History
Gabon was a French colony when prospectors from the French nuclear energy commissariatCommissariat à l'Énergie Atomique
The Commissariat à l'énergie atomique et aux énergies alternatives or CEA, is a French “public establishment related to industrial and commercial activities” whose mission is to develop all applications of nuclear power, both civilian and military...
(the industrial parts, which later became the COGEMA and later Areva NC
Areva NC
Areva NC, formerly Cogema is a French company, created in 1976 from the production division of the French government's CEA It is an industrial group active in all stages of the uranium fuel cycle, including uranium mining, conversion, enrichment, spent fuel reprocessing, and recycling...
) discovered uranium in the remote region in 1956. France immediately opened mines operated by Comuf (Compagnie des Mines d'Uranium de Franceville) near Mounana
Mounana
Mounana is a town in Gabon with a population of about 8,000 people. It lies on the N3 road and from 1958 until the 1990s was a major uranium mining centre. The mine is now closed; it is now primarily a centre for agriculture....
village in order to exploit the vast mineral resources and the State of Gabon was given a minority share in the company.
For forty years, France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
mined for uranium in Gabon. Once extracted, the uranium was used for electricity production in France and much of Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
. Today, however, the uranium deposits are exhausted, and the mine is no longer worked. Currently, mine reclamation
Mine reclamation
Mine reclamation is the process of creating useful landscapes that meet a variety of goals, typically creating productive ecosystems from mined land...
work is ongoing in the region affected by the mine operations.
There is strong geochemical evidence that the Oklo uranium deposit behaved as a natural nuclear fission reactor
Natural nuclear fission reactor
A natural nuclear fission reactor is a uranium deposit where analysis of isotope ratios has shown that self-sustaining nuclear chain reactions have occurred. The existence of this phenomenon was discovered in 1972 at Oklo in Gabon, Africa, by French physicist Francis Perrin. The conditions under...
in Precambrian
Precambrian
The Precambrian is the name which describes the large span of time in Earth's history before the current Phanerozoic Eon, and is a Supereon divided into several eons of the geologic time scale...
times: some of the mined uranium was found to have a lower concentration of uranium-235
Uranium-235
- References :* .* DOE Fundamentals handbook: Nuclear Physics and Reactor theory , .* A piece of U-235 the size of a grain of rice can produce energy equal to that contained in three tons of coal or fourteen barrels of oil. -External links:* * * one of the earliest articles on U-235 for the...
than expected, as if it had already been in a reactor. Geologists found that it had been in a reactor before—two billion years ago. At that time the natural uranium had a concentration of about 3% 235U, and could have gone critical
Critical mass
A critical mass is the smallest amount of fissile material needed for a sustained nuclear chain reaction. The critical mass of a fissionable material depends upon its nuclear properties A critical mass is the smallest amount of fissile material needed for a sustained nuclear chain reaction. The...
with natural water as neutron moderator
Neutron moderator
In nuclear engineering, a neutron moderator is a medium that reduces the speed of fast neutrons, thereby turning them into thermal neutrons capable of sustaining a nuclear chain reaction involving uranium-235....
.
See also
- List of uranium mines
- Natural nuclear fission reactorNatural nuclear fission reactorA natural nuclear fission reactor is a uranium deposit where analysis of isotope ratios has shown that self-sustaining nuclear chain reactions have occurred. The existence of this phenomenon was discovered in 1972 at Oklo in Gabon, Africa, by French physicist Francis Perrin. The conditions under...
- Deep geological repositoryDeep geological repositoryA deep geological repository is a nuclear waste repository excavated deep within a stable geologic environment...