Since the nuclear reactors were discovered in 1972 in Gabon, scientists have been scratching their heads trying to understand how it is possible that these nuclear reactors developed in Gabon two billion years ago, and did not develop at any other place on the Planet.
It’s no joke that two billion years ago, parts of an African uranium deposit spontaneously underwent nuclear fission, how well conditions just happened to be perfect and “something occurred”. According to scientists, this mysterious “natural” nuclear reactor had the ability to produce modest energy.
Scientists estimate the Oklo reactors would have had samples with roughly 3.6% uranium-235 — that’s close to the enrichment threshold of modern nuclear reactors.
Putting things into perspective, the average power produced by the 2-billion-year-old nuclear reactor is around 100 kilowatts, or at least that’s what researchers believe.
Researchers now know that around 2 billion years ago, the nuclear reactor located at Oklo began operation “spontaneously.” The interesting part is that this nuclear reactor continued operating in a stable manner for up to one million years, but how is this possible? What trigger this incredible phenomena?
More interestingly, most of the products of the nuclear fission were safely contained for two billion years, meaning that extreme conditions which had to be more than “perfect” had to be met in order to allow something like this to happen.
Scientists performed several other investigation at the uranium mine and the results were made public at a conference of the International Atomic Energy Agency. According to News agencies from Africa, researchers had found traces of fission products and fuel wastes at various locations within the mine. Incredibly, compared with this huge nuclear reactor, our modern-day nuclear reactors are really not comparable both in design and functionality. According to studies, this ancient nuclear reactor was several kilometers long. Interestingly, for a large nuclear reactor like this, thermal impact towards the environment was limited to just 40 meters on the sides.
Researchers hypothesized in the 1950’s that nuclear reactors may have operated on the ancient Earth in the distant past.
Researchers believe that nuclear reactors are unique. You won’t find a bunch of them and for them to occur, specific conditions must be met. Here are four conditions which must be met in order for a stable natural nuclear reactor to develop:
1. The natural uranium ore must have a high uranium content and must have a thickness (at least ~2/3 of a meter) and geometry that increase the probability of spontaneous, natural fission in uranium-238 inducing a self-sustaining fission reaction in uranium-235.
2. The uranium must contain significant amount of fissionable uranium-235.
3. There must be a moderator, something that can slow down the neutrons produced when uranium fissions.
4. There must not be significant amounts of neutron-absorbing elements (such as silver or boron), which would inhibit a self-sustaining nuclear reaction, in the vicinity of the uranium.
Dr. Glenn T. Seaborg, former head of the United States Atomic Energy Commission and Nobel Prize winner for his work in the synthesis of heavy elements, pointed out that for uranium to “burn” in a reaction, conditions must be exactly right. For example, the water involved in the nuclear reaction must be extremely pure. Even a few parts per million of contaminant will “poison” the reaction, bringing it to a halt. The problem is that, no water that pure exists naturally anywhere in the world.
Source and reference: Blogs – Scientific American