How Discovery of a 2 Billion Year Old Nuclear Reactor in Africa Stunned the World

In June 1972, nuclear scientists at the Pierrelatte uranium enrichment plant in south-east France noticed something suspicious in the amount of uranium 235 they were processing. In uranium enrichment plants where every gram of fissionable material has to be carefully accounted for that is a serious problem. For weeks, specialists at the French Atomic Energy Commission remained perplexed.

The problem lay in the ratio of uranium isotopes in their samples. Natural uranium contains three isotopes, always in the same ratios: uranium 238 (99.2744 per cent), uranium 235 (0.7202 per cent) and uranium 234 (0.0054 per cent).

The problem was with the uranium 235, there was only 0.600 per cent.

Physicists soon traced the anomaly to the supply of uranium ore from Gabon in West Africa, which contained far less uranium 235 than the ore from anywhere else on the planet, a problem that caused some consternation among nuclear scientists.

So France’s top nuclear scientists began an investigation and, in the process, made one of the more remarkable discoveries in recent history.

On 25 September 1972, they announced that the depleted uranium had come from Gabon where nuclear scientists had discovered a 2 billion year-old nuclear reactor at the site of the Oklo uranium mines near a town called Franceville. This was a naturally occurring deposit of uranium where the concentration of uranium 235 had been high enough to trigger a self-sustaining nuclear reaction.

The first puzzle that physicists had to deal with was how a naturally-occurring reactor could work at all. Nuclear scientists well know that reactors do not work with natural uranium because the level of uranium 235 is too low at only 0.7202 per cent. Instead, the uranium 235 has to be enriched so that it is about 3.5 per cent of the total. So how did such a phenomenon end up at Oklo?

This discovery shocked the world and led many scientists to believe that the uranium had already been used for energy production. The results of the investigation revealed that the uranium mine was an ancient nuclear reactor with a very rational layout that was constructed 2 billion years ago and was in operation for 500,000 years.

Another incredible fact is that the nuclear wastes produced in this reactor had not moved outside the boundaries of the site but confined within the separate sections. In terms of design and functionality, our modern-day nuclear reactors simply cannot be compared with this mega-reactor. This discovery raises the intriguing possibility of a technologically more advanced civilization that existed 2-billion years ago.

Oklo has also become the focus of physicists studying the possibility that the universe’s fundamental constants may have changed over time. The reason that Oklo may be able to help is that it stopped operating over 1.5 billion years ago. So the nuclear processes that occurred at that time must have been governed by the fundamental constants as they were then.

After the initial hype in the Oklo story, it gradually fizzled out. Driven by the intense interest in the early 1970s, mining continued at Oklo and eventually all the natural reactors were mined out. The one exception was a shallow reactor zone at a place called Bangombé, some 30 kilometres from Oklo, although this has largely been washed out by ground water.

So these zones have been largely lost to science which is a pity. It also means that nuclear scientists are unlikely to get better data on natural nuclear reactors using the advanced techniques than those of available in the 1970s.

How do we view such a discovery? There are Doubting Thomas’s who put down everything that science cannot prove and are sceptical about carbon dating. Many experts today, agree that prehistoric civilizations far more advanced than ours existed on this Earth millions of years ago. There is plenty of evidence which suggests that long before history was being written, extremely advanced civilizations existed in the past and left behind numerous clues all over the world. If we disapprove or neglect the relics of prehistoric civilizations, there is no way we can broaden the scope of our present knowledge.

Suren Rao