In a groundbreaking discovery over fifty years ago, geologists uncovered an astonishing natural nuclear reactor in the depths of the African Oklo region. This rare section of the earth’s crust held evidence of nuclear reactions that took place long before humans even existed.
The journey to this discovery began in 1972, when a French physicist working at a uranium enterprise in Pierlatt came across unusual mineral samples from African deposits. Upon closer examination, the scientist noticed a significant deviation in the composition of uranium isotopes, challenging established scientific norms.
Typically, natural uranium deposits contain about 0.720 percent uranium-235. However, samples from Oklo displayed a lower percentage of 0.717. Despite the small difference, this discrepancy became a crucial clue for researchers.
Further investigations uncovered more anomalies, with some sections of the deposit showing uranium-235 levels as low as 0.4 percent. This led to the hypothesis of a natural nuclear reactor operating around two billion years ago.
The reactor functioned similarly to modern nuclear stations, with underground water likely serving as a neutron moderator, akin to water in contemporary reactors. The heating and cooling cycle of the water initiated and ceased the nuclear reaction.
Confirmation of this unique find came from the International Atomic Energy Agency, which identified rare-earth isotopes and specific crypton and xenon spectra as undeniable proof of the reactor’s existence.
While the natural nuclear reactor in Africa operated for thousands of years before gradually diminishing, replicating such a phenomenon today is nearly impossible due to changes in uranium composition and geological conditions. This discovery underscores the intricate and unpredictable nature of natural processes.
Rocks samples from the Oklo deposit are now preserved at the headquarters of the French company Orano, specializing in nuclear and renewable energy. In early 2018, two drilling core fragments were gifted to the natural history museum in Vienna, with careful monitoring by Magate scientists to ensure safe handling due to the low levels of radiation emitted.
These seemingly ordinary stones from Oklo emit around 40 microsieverts per hour at a 5-centimeter distance, comparable to the cosmic radiation dose received during an eight-hour flight from Vienna to New York.