Natural nuclear fission reactor

A natural nuclear fission reactor is a <a href="/facts/Uranium/n2sGWBzU">uranium</a> <a href="/facts/Mineral_deposit/kgc9DssX">deposit</a> where self-sustaining <a href="/facts/Nuclear_chain_reaction/3l0lHBM4">nuclear chain reactions</a> occur. The idea of a <a href="/facts/Nuclear_reactor/8xqjIbge">nuclear reactor</a> existing in situ within an ore body moderated by groundwater was briefly explored by <a href="/facts/Paul_Kuroda/esNyAQX2">Paul Kuroda</a> in 1956. The existence of an extinct or fossil nuclear fission reactor, where self-sustaining nuclear reactions have occurred in the past, are established by analysis of <a href="/facts/Isotope/KD9B1y6o">isotope</a> <a href="/facts/Ratio/mFmhQt7T">ratios</a> of uranium and of the <a href="/facts/Fission_product/xJd9MXXH">fission products</a> (and the stable <a href="/facts/Daughter_nuclide/hT0obfLv">daughter nuclides</a> of those fission products). The first discovery of such a reactor happened in 1972 in <a href="/facts/Oklo/p2jg2BuS">Oklo</a>, <a href="/facts/Gabon/RKDffnwV">Gabon</a>, by researchers from the <a href="/facts/French_Alternative_Energies_and_Atomic_Energy_Commission/YPwAJk03">French Alternative Energies and Atomic Energy Commission</a> (CEA) when chemists performing quality control for the French nuclear industry noticed sharp depletions of <a href="/facts/Fissile/XJR9qoxW">fissile</a> <a href="/facts/Uranium-235/pe0RznDM">235U</a> in gaseous uranium made from Gabonese ore.
Oklo is the only location where this phenomenon is known to have occurred, and consists of 16 sites with patches of centimeter-sized <a href="/facts/Ore_deposit/kgc9DssX">ore layers</a>. There, self-sustaining <a href="/facts/Nuclear_fission/LfkIylvm">nuclear fission</a> reactions are thought to have taken place approximately 1.7 <a href="/facts/Billion/d9KjEYSt">billion</a> years ago, during the <a href="/facts/Statherian/LHcg66kG">Statherian</a> period of the <a href="/facts/Paleoproterozoic/gMS69p5r">Paleoproterozoic</a>. Fission in the ore at Oklo continued off and on for a few hundred thousand years and probably never exceeded 100 <a href="/facts/Watt/VK8oqRrm">kW</a> of thermal power. Life on Earth at this time consisted largely of sea-bound <a href="/facts/Algae/U1ftVKU3">algae</a> and the first <a href="/facts/Eukaryote/SkwyPLMA">eukaryotes</a>, living under a 2% <a href="/facts/Oxygen/acyn6o8r">oxygen</a> atmosphere. However even this meager oxygen was likely essential to the concentration of uranium into fissionable ore bodies, as uranium dissolves in water only in the presence of oxygen. Before the planetary-scale production of oxygen by the early <a href="/facts/Photosynthesis/TMV7w693">photosynthesizers</a> groundwater-moderated natural nuclear reactors are not thought to have been possible.

Natural nuclear fission reactor open-in-new

Natural nuclear fission reactor