Image credit: US Department of Energy Natural Fission Oklo natural reactor as seen in underground mining operations. In 1997 Francois Gauthier-Lafaye wrote a plea to the journal Nature, advocating that mining of the Bangombé uranium be stopped. In the late 1990s, there was danger that the last natural nuclear reactor at Bangombé would be mined as well. Only a limited number of specimens remained that were made available for study. An additional seventeenth natural nuclear reactor was also discovered at Bangombé, located about 30km to the south-east of Oklo.īy the time the significance of the discovery was realised by the scientific community, the sixteen natural nuclear reactors at Oklo had been destroyed, completely mined out for their rich uranium ore. Further exploration discovered sixteen natural nuclear reactors in uranium mines at Oklo. It was considered very important to the officials to account for this ‘missing’ uranium-235. However, there were high concentrations of elements like cesium, curium, americium and even plutonium to be found. The uranium ore was anomalously depleted in uranium-235, containing only 0.717%. During a routine isotopic measurement of uranium ore from Gabon, it was noticed that the uranium ore did not have a uranium-235 content of 0.720% as most other known deposits. The French had been mining uranium in Gabon, at Oklo, for several years to utilise in their nuclear power plants. The probability of natural fission was theorised by Paul Kuroda in a 1956 paper, but not proven until seventeen natural fission sites were discovered in Gabon in 1972 and became commonly known as the ‘Gabon Reactors’. The first man-made nuclear fission plants were only developed in the 1950s. As the Oklo-reactor demonstrates, the ruthenium-compounds remain stable even if exposed to radioactivity and corrosion by water over vast geological periods.Oklo natural reactor as seen in underground mining operations. If so, containers made of ruthenium alloys could be used to safely store radioactive waste for a very long time. The scientists believe that the radioactive plutonium and cesium were encapsulated and safely isolated from the environment by a shell of ruthenium-compounds. Native ruthenium is a rare and inert metal often associated with ore of other elements. In rocks recovered from the Oklo mine, barium (the 'trace' left by the former radioactive elements) is not found evenly distributed, but rather found in nests surrounded by a thin layer of ruthenium-compounds. and published in the journal PNAS has investigated how the Oklo-reactor was able to work so long and yet not pollute the environment. Research by a team of scientists of the US Naval Research Laboratory in Washington D. By studying the Oklo-reactor, scientists hope to find a way to safely dispose of nuclear waste as produced by modern reactors. Steel will rust, concrete can leak and even glass is damaged by the emitted radiation. The problem is that we don't know what materials to use for the containers to store the waste. A permanent repository for nuclear waste must contain toxic elements and radioactivity for at least 100,000 years. Many experts believe that nuclear energy could be a temporary solution until renewable energy sources are ready to meet the demand. Unfortunately, nuclear energy comes with radioactive waste. During this process, however, no harmful radioactivity has leaked into the environment.Īs t he planet warms due to our carbon emissions, burning oil and coal is no longer a sustainable way to meet humanity’s hunger for energy. Over time the Oklo-reactor has produced large quantities of toxic plutonium and cesium-isotopes, which have since decayed into stable and harmless barium. As the uranium decays, it forms other radioactive elements fueling the reactor. Then water that infiltrated the formation along faults slowed down the emitted neutrons enough to sustain slow and stable nuclear fission. Weathering of magmatic rocks and bacterial activity concentrated the uranium enough to start a nuclear chain reaction. In the Oklo-reactor, two factors came together to sustain a slow nuclear fission for hundreds of thousands of years.
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