J., 1978, U-Pb age (2.05 × 10 9 years) of the Oklo uranium deposit: in IAEA, p. C., 1976, Conclusions tirées de l'étude de la migration des produits de fission: in IAEA, p. 28–37.įréjacques, C., Blain, C., Devilliers, C., Hagemann, R., and Ruffenbach, J. J., 1974, Heavy rare gases from Rabbit Lake (Canada) and the Oklo mine (Gabon): natural spontaneous chain reactions in old uranium deposits: Earth Plan. L., 1980, The Oklo natural reactor: cumulative fission yields and retentivity of the symmetric mass region fission products: Earth Plan. G., ed., Loading and leachage of krypton immobilized in zeolites and glass: Basis Nuclear Wste. L., 1976, Search for fission-produced Rb, Sr, Cs and Ba at Oklo: in IAEA, p. G., 1981, Alkali and alkaline earth studies at Oklo: in Moore, J. G., 1980, Syngenetic model for some early Proterozoic uranium deposits: evidence from Oklo: Int. G., 1978c, Application of Eh-pH diagrams to problems of retention and/or migration of fissiogenic elements at Oklo: in IAEA, p.

G., 1978b, Retention of transuranic and actinide elements and bismuth at the Oklo natural reactor, Gabon: Chem. G., 1978a, Eh-pH diagrams for elements from Z=40 to Z=52: application to the Oklo natural reactor: Chem. 278–403.īonhomme, M., Leclerc, J., and Weber, F., 1978, Etude radiochronologique complémentaire de la série du Francevillien et de son environment: in IAEA p.

L., ed., Geochemistry of Hydrothermal Ore Deposits, 2nd Ed.: New York, Wiley-Interscience, p. J., 1979, Sulfide mineral stabilities: in Barnes, H. This suggests that rocks with more favorable geologic characteristics are indeed well suited for consideration for the storage of radioactive waste.Īllard, B., Torstenfelt, B., Andersson, K., and Rydberg, J., 1980, Possible retention of iodine in the ground, in Northrup, C. An element by element assessment of the Oklo rocks' ability to retain the fission products, and actinides and radiogenic Pb and Bi as well, leads to the conclusion that no widespread migration of the elements occurred. Only Xe and Kr have apparently been largely removed from the reactor zones. Since reactor shutdown, many fissiogenic elements have not migrated from host pitchblende, and several others have migrated only a few tens of meters from the reactor ore. The many tons of fission products can, for the most part, be studied for their abundance and distribution today. The uranium ore that sustained fission reactions formed about 2 billion years before present (BYBP), and the reactor was operative for about 5 × 10 5 yrs between about 1.95 to 2 BYBP. 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.The Oklo natural reactor, Gabon, permits study of fission-produced elemental behavior in a natural geologic environment. 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. When geologists investigated they also found products typical of a 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 reactor.

Currently, mine reclamation work is ongoing in the region affected by the mine operations. Today the uranium deposits are exhausted, and the mine is no longer worked. Once extracted, the uranium was used for electricity production in France and much of Europe. France immediately opened mines operated by Comuf ( Compagnie des Mines d'Uranium de Franceville code: fra promoted to code: fr ) near Mounana village to exploit the vast mineral resources, and the State of Gabon was given a minority share in the company.įor 40 years, France mined uranium in Gabon. 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. Several natural nuclear fission reactors were discovered in the uranium mines in the region in 1972. Oklo is a region near the town of Franceville, in the Haut-Ogooué province of the Central African country of Gabon.