Examining the overlooked implications of natural reactors

Abstract

On April 7,1972, scientists at the French Atomic Energy Establishment at Pierrelatte discovered a 0.4% anomaly in the uranium isotopic ratio of a sample of natural uranium. In a masterful example of analytical detective work, the French scientists traced the anomaly to a particular area of a uranium mine located at Oklo in the Republic of Gabon. In that area they found uranium that was deficient in U‐235 and was accompanied by fission‐produced isotopes of Nd and Sm. On September 25, 1972, the French Atomic Energy Commission announced their conclusion that self‐sustaining nuclear chain reactions had occurred on Earth about 2000 million years ago [Neuilly et al., 1972]. Later, other natural nuclear fission reactors were discovered in the region [Gauthier‐Lafaye et al., 1996].