A routine analysis of uranium sample at Pierrelatte in 1972 showed a discrepancy of 0·003% in the content of 235U. This was the starting point of a remarkable scientific detective story involving physicists chemists, geologists mineralogists, geochemists and lunar sample analysts. It led to the identification and detailed exploration of the site of a natural fission reactor. The reactor was operating for about 700 000 year approximately 1800 million year ago, releasing about 15000 megawatt-years of energy, and traces of its activity have been fully preserved. The following is the first full description of the Oklo phenomenon to be published in English.
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References
1.
(a)KurodaP. K., On the nuclear physical stability of the uranium minerals.J. Chem. Phys. 25, 781 (1956); (b) F. Weber, Une série précambrienne au Gabon; le franceviltien. Thesis presented to the Faculty of Sciences, Strasbourg University, France (1969).
2.
BoduR., BouziguesH., MorinN. and PfifelmanJ, P., Sur l'existence d'anomalies isotopiques rencontrées dans l'uranium du Gabon. C.R. Acad. Sei. Paris. Ser. D. 275, 1731 (1972).
3.
NeuillyM., BussacJ., FrejacquesC., NiefG., VendryesG. and YvonJ., Sur l'existence dans un passé reculé d'une réaction en chaîne naturelle de fissions, dans le gisement d'uranium d'Oklo (Gabon). C.R. Acad. Sci. Paris, Ser. D275, 1847 (1972).
4.
BaudinG., BlainC., HagemannR., KremerM., LucasM., MerlivatL, MolinaR., NiefG., Prost-MarechalF., RegnaudF. and RothE., Quelques données nouvelles sur les réactions nucléaires en chaîne qui se sont produites dans le gisement d'Oklo. C.R. Acad. Sci. Paris, Ser. D. 275, 2291 (1972).
5.
NaudetR., Les réacteurs naturels d'Oklo. Bilan au 1er Mai 1974. Bulletin d'informations Scientifiques et Techniques du C.E.A, ParisNo. 193, (Juin1974); Oklo: des reacteurs fossiles. La Recherche 6, 508 (1975); Le phénomène d'Oklo. Rev. Gen Nucléaire 1, 45 (1975); See also the following brief notes on theOklo phenomenon: I.A.E.A.B. 17, No. 1, 22 (1975) and 17, No. 3, 2 (1975); Sci. Am. 41 (June 1975); Nature 256, 264 (1975); Phys. Bull. 391 (September 1975); J. A. Goedkoop, Atoomenergie 17, 260 (1975).
6.
SlodzianG. and HavetteA., Ion microanalyses observation of samples from the natural reactor of Oklo; preliminary results. In: Advances in Mass Spectrometry, Vol. 6, edited byWestA. R., p. 629. Applied Science Publishers, Barking, Essex (1974).
7.
DrozdR. J., HohenbergC. M. and MorganC. J., Heavy rare gases from Rabbit Lake (Canada) and the Oklo mine (Gabon): natural spontaneous chain reactions in old uranium deposits. Earth Planet. Sci. Lett. 23, 28 (1974).
8.
HagemannR., LucasM., NiefG. and RothE., Mesures isotopiques du rubidium et du strontium et essais de mesure de l’âge de la minéralisation de l'uranium du réacteur naturel fossile d'Oklo. Earth Planet, Sci. Lett. 23, 170 (1975).
9.
LancelotJ. R., VitracA. and AllegreC. J., The Oklo natural reactor—Age and evolution studies by U-Pb and Rb-Sr systematics. Earth Planet, Sci. Lett. 35, 189 (1975).
10.
MolinaP. and De TreyM., Place of the Franceville basin in the geology of Africa, IAEA-SM 204/35.
11.
WeberG. and BonhommeM. C., New geochronological date on the Franceville basin and the surrounding region. IAEA-SM 204/16.
12.
PfiffelmannJ. P., The uraniferous zone in the Franceville basin. IAEA-SM 204/33.
13.
ChauvetR. J., Description of the Oklo uranium deposit. IAEA-SM 204/34.
14.
BoyerR. and NaudetR., Exploration of the Oklo reaction sites, IAEA-SM 204/20.
15.
NaudetR., FilipA. and RensonC., Detailed distribution of the uranium within the lodes. IAEA-SM 204/21.
16.
Gauthier-LafayeF., RuhlandM. and WeberF., Tectonic analysis of the Oklo deposit. IAEA-SM 204/15.
17.
BrancheG., ChantretF. and GuillemautA., Mineralogy and chemistry of the Oklo deposit. IAEA-SM 204/17.
18.
GeffroyJ. and LemercierMlle, Metallogenic study of the Oklo ores. IAEA-SM 204/18.
19.
Le MercierM., GeffroyJ. and WeberF., Summary of the mineralogical and petrographic studies of the Oklo ores, their gangues and the country rock, IAEA-SM 204/14.
20.
CassouA. M., ConnanJ., CorreiaM. and OrgevalJ. J., Observations concerning the organic matter associated with the uranium ores in the Franceville basin. IAEA-SM 204/19.
21.
DurraniS. A., HwangF. S. W., MalikS. R., KhazalK. A. E. and FremlinJ. H., Thermoluminescence and track analysts studies of the Oklo fossil reactor materials. IAEA-SM 204/6.
22.
BurltngamA., DranJ. C., MauretteM., DuraudJ. P., Le GressusC. and MassignonD., Microdistribution of radiation damage and of certain elements—carbon chemistry and noble gas distribution, IAEA-SM 204/12.
23.
BouziguesH. V., SeyveC. and TeulieresP. L., Contribution to the solution of a scientific enigma. IAEA-SM 204/36.
24.
BoyerR. and TeulieresP., Precision and sensitivity of the isotopic analysis of the uranium contained in the Oklo ores. IAEA-SM 204/37.
25.
BoyerR., GueryM. and RensonC., Apparatus used at Oklo for determining the isotopic composition of the uranium. IAEA-SM 204/22.
26.
NaudetR. and RensonC.. Results of systematic analyses of the isotopic composition of the uranium. IAEA-SM 204/23.
27.
AllegreC. J., LoubetM., LancelotJ. and VitracA., Chronometric relationships, nuclear characteristics and geochemical evolution of the Oklo natural reactor, IAEA-SM 204/11.
28.
KruglovA. K., PchelkinV. A., SviderskijM., DymkovYu M., MoshechanskayaG. N. and ChernetsovO. K., Preliminary investigations of samples of uranium ore from the Oklo natural reactor in Gabon. IAEA-SM 204/8 (In Russian).
29.
DevillersC., RuffenachJ. C., MenesJ., LucasM., HagemannR. and NiefG., Age of the uranium ores and date of the nuclear reaction. IAEA-SM 204/26.
30.
MaeckW. J., Absolute fast fission yields, stable fission product isotope ratios, and yield-energy correlations applicable to the evaluation of Oklo fission product data. IAEA-SM 204/2.
31.
CowanG. A., BryantE. A., DanielsW. R. and MaeckW. J.. Some U.S. studies of the Oklo phenomenon. IAEA-SM 204/5.
32.
DozolJ. F. and NeuillyM., Isotopic analysis of the rare earths contained in the Oklo ores. IAEA-SM 204/29.
33.
RuffenachJ. C., LucasM., MenesJ., HagemannR. and NiefG., Fine isotopic analyses of fission products and determination of the main parameters of the nuclear reaction. IAEA-SM 204/27.
34.
CesarioJ. R., BassièreH. and PoupardD., Determination of rare earths by isotopic dilution of samples from Oklo. IAEA-SM 204/31.
35.
BrookinsD. G., LeeM. J., MukhopadhyayB. and BolivarS. L., Search for fission produced Rb, Sr, Cs and Ba at Oklo. IAEA-SM 204/3.
36.
HagemannR., DevillersC., LucasM., LecomteT. and RuffenachJ. C., Estimation of the duration of the reaction—limitations imposed by the neutron data. IAEA-SM 204/28.
37.
de LaeterJ. R. and RosmanK. J. R., Cumulative fission yields of cadmium in Oklo samples. IAEA-SM 204/7.
38.
HérmonG., ManetA. and PhilipottJ. C., Fine γ spectrometry before and after activation on ore samples from Oklo. IAEA-SM 204/32.
39.
HavetteA. and SlodzianG., Study by ion analysis of the distribution and the isotopic proportions of certain elements in samples from Oklo, IAEA-SM 204/13.
40.
RothE., LucasM., LecomteT., DevillersC. and HagemannR., Attempt at contributing by isotopic geochemistry to an evaluation of the importance and frequency of phenomena of the Oklo type. IAEA-SM 204/25.
41.
WaltonR. D.Jr, The relevance of nuclide migration at Oklo to the problem of geological storage of radioactive waste. IAEA-SM 204/1.
42.
FréjacquesC., Conclusions drawn from study of the migration of fission products. IAEA-SM 204/24.
43.
NaudetR. and FilipA., Study of the neutron balance of the natural reactors at Oklo. IAEA-SM 204/38.
44.
NeuillyM. and NaudetR.. Study of the fluence distribution in the natural reactors at Oklo by isotopic analysis of rare earths. IAEA-SM 204/30.
45.
NaudetR. and ReussP., Neutron-based interpretation of the reaction rate distributions in the Oklo reactors. IAEA-SM 204/39.
46.
NaudetR. and ReussP., Models of uranium and fission product behaviour. IAEA-SM 204/40.
47.
NaudetR., Problems posed by the mechanisms regulating the reactions. IAEA-SM 204/41.
48.
KurodaP. K., Fossil nuclear reactor and plutonium-244 in the early history of the solar system. IAEA-SM 204/4.
