The reactor that began without human intervention

Can a uranium deposit begin self-sustaining nuclear reactions without human intervention? In 1972, while analyzing uranium which had been mined in Gabon, Africa, some French scientists discovered some uranium which had an abnormally small percentage of the isotope U-235 as compared to U-238. In most uranium 0.72% is U-235, and no natural uranium had ever previously been discovered which was more than 0.1% different from 0.72%. In trying to explain why the particular ore they were analyzing was different, the French scientists were led to the hypothesis that a fission chain reaction had occurred in this ore, hence a natural reactor had existed long before man ever discovered fission or built a nuclear reactor. Since they also hypothesized that the reactor was about 2 billion years old, it is of interest to biblical creationists to find out whether the numerical data that were gathered could also be explained in a biblical time frame or whether it is evidence for accelerated nuclear decay.

According to the Geologic Time Table, of conventional historic geology, the Oklo surface rocks are Precambrian strata. Thus, they would represent the rocks present before the Cambrian “explosion” which shows the sudden appearance of multi-celled plants and animals. In many creationist models, the Precambrian rocks at Oklo would be either the lowest lying sediments from the Flood, or else the pre-Flood rocks. Since the reactors were found in some steeply dipping sandstone sediments (figure 1), their exact time of placement is not certain, and the nuclear reactions could have occurred after the sandstone deposition, but they would represent an early stage of earth history in any credible scenario.

At Oklo, the first reactor zones discovered were in a strip mine. In 1975 a scientific meeting was held in Gabon, which included some sessions on benches in the strip mine next to the reactor deposits. Participants observed the exposed rocks inside the strip mine including uranium oxide deposits. Since the conference, more than a dozen reactor zones have been discovered at Oklo, and others about 20 km south of Oklo (figure 2). Today, water fills the Oklo mine’s pit, which was permitted to flood, even covering the sites of the reactors, after the mine’s uranium ore had been exploited.

The fission process

Nuclear fission begins when a nucleus deforms. The deformation may be produced when a nucleus absorbs a neutron, resulting in an excited nucleus with extra energy. The situation is often compared to a charged liquid drop. As the drop oscillates it may assume a peanut shape, which, because of the positive charge on both ends, then splits in two. The nuclear force of attraction between nuclear particles is short ranged, hence after the drop is split apart the only force left is the repulsive electrical force, and the two parts must repel each other. The two fragments then emit neutrons and photons. The neutrons may go on to cause more fissions. If the number of neutrons is enough, a self-sustaining chain reaction will result, which we call a nuclear reactor. One result of all this fission is a lot of fission fragments, i.e. smaller nuclei produced when the uranium splits. Any viable theory explaining the Oklo deposits must therefore be able to explain and correlate two sets of data. One is the amount of different forms (isotopes) of the fission-product elements remaining in the reactor at Oklo at present, and the other is the amount of uranium found in the ore. Both of these sets of data, plus a theory, gives us estimates of the amount of fission that has occurred, and both sets of data must result in the same estimate if the theory is correct….

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