Wednesday, 18 March 2015

Ancient nuclear reactor found in Gabon

Ancient nuclear reactor found in Gabon
Many years ago before the first commercial nuclear power plants was developed in the 1950s about 17 natural nuclear fission reactors operated in what is today known as Gabon. A natural nuclear fission reactor is a uranium deposit where self-sustaining nuclear chain reactions have occurred. This is usually identified through analysis of isotope ratios. The conditions under which a natural nuclear reactor could exist had been predicted in 1956 by Paul Kazuo Kuroda.
In 1972 a French physicist Francis Perrin discovered the existence of this phenomenon at Oklo in Gabon, Africa. Oklo is the only known location for this in the world and consists of 16 sites at which self-sustaining nuclear fission reactions took place approximately 1.7 billion years ago, and ran for a few hundred thousand years, averaging 100 kW of thermal power during that time (which would power about 1,000 lightbulbs).
The energy produced by these natural nuclear reactors was modest compared to the commercial nuclear power plants, which produce about 1,000 megawatts that would power about ten million lightbulbs.
The Gabon nuclear reactor was discovered when the French who had been mining uranium in Gabon for use in nuclear power plants. During a routine isotopic measurement of uranium ore from the Oklo site, the French noticed something very strange: the uranium ore did not have a uranium-235 content of 0.720%. Rather, the uranium ore was anomalously depleted in uranium-235, containing only 0.717%. The discrepancy though quite small was very alarming for the French nuclear officials, as uranium-235 in Earth’s crust, in moon rocks and in meteorites varies very little from the average value of 0.720%. Since uranium-235 can be used to make nuclear bombs, it was very important to account for this “missing” uranium-235.
The nuclear officials and scientists eventually remembered the old publications of Kuroda and others, and soon realised that the anomalous uranium from Gabon provided evidence of something extraordinary—the first natural nuclear reactor ever discovered. Eventually, sixteen natural nuclear reactors were discovered in uranium mines at Oklo. An additional seventeenth natural nuclear reactor was also discovered at Bangombé, located about 30 km to the southeast of Oklo.
Since the discovery of the Gabon natural nuclear reactors in 1972, scientists have been puzzling over why these reactors developed only in Gabon and no other place on Earth.  Scientists are still working to understand the Gabon reactors, but over the past forty years, they have managed to tease out some of the details of how these nuclear reactors operated and were preserved in the geologic record.
But one question that is yet to be answered is whether the reactors were operated by intelligent beings that have inhabited the Oklo area during that period of time.

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Additional information from Scientific American

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