7/31/2023 0 Comments Fission reactorOther observations led to the same conclusion, and on 25 September 1972 the CEA announced their finding that self-sustaining nuclear chain reactions had occurred on Earth about 2 billion years ago. A possible explanation was that the uranium ore had operated as a natural fission reactor in the distant geological past. Is exactly what happens in a nuclear reactor. U must have also been present in higher than usual ratios during the time the reactor was operating, but due to its half life of 2.348 ×10 7 years being almost two orders of magnitude shorter than the time elapsed since the reactor operated, it has decayed to roughly 1.4 ×10 −22 its original value and thus basically nothing and below any abilities of current equipment to detect. U concentration present at the time the reactor was active would have long since decayed away. U by fast neutron induced (n,2n) reactions in nuclear reactors. U and due to it being both consumed by neutron capture and produced from 235 U concentrations significantly different from the secular equilibrium of 55 ppm 234 Both depleted uranium and reprocessed uranium will usually have 234 U did not deviate significantly in its concentration from other natural samples. Subsequent examination of isotopes of fission products such as neodymium and ruthenium also showed anomalies, as described in more detail below. Further investigations into this uranium deposit discovered uranium ore with a 235Ĭoncentration as low as 0.44% (almost 40% below the normal value). A series of measurements of the relative abundances of the two most significant isotopes of the uranium mined at Oklo showed anomalous results compared to those obtained for uranium from other mines. Thus the French Commissariat à l'énergie atomique (CEA) began an investigation. Furthermore since fissile material is why people mine uranium, a significant amount "going missing" was also of direct economic concern. This discrepancy required explanation, as all civilian uranium handling facilities must meticulously account for all fissionable isotopes to ensure that none are diverted to the construction of nuclear weapons. Normally the concentration is 0.72% while these samples had only 0.60%, a significant difference (some 17% less U-235 was contained in the samples than expected). In May 1972 at the Tricastin uranium enrichment site at Pierrelatte in France, routine mass spectrometry comparing UF 6 samples from Oklo showed a discrepancy in the amount of the 235 It is estimated to have averaged under 100 kW of thermal power during that time. Oklo consists of 16 sites at which self-sustaining nuclear fission reactions are thought to have taken place approximately 1.7 billion years ago, and ran for hundreds of thousands of years. Oklo Mine (sometimes Oklo Reactor or Oklo Mines), located in Oklo, Gabon on the west coast of Central Africa, is believed to be the only natural nuclear fission reactor.
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