Earth’s “Natural” Nuclear Reactor
By: Nathan Vargh
Tags: Chemistry, Nuclear, Science, Research, Biology

To many people, nuclear energy is just about as unnatural as you can get when it comes to renewable energy. Nuclear power has the potential for nuclear energy to deliver stable and sustainable returns for minimal costs compared to other renewable energy sources. However, when people are scared of nuclear power, it doesn’t matter how much nuclear energy benefits. That being said, I don’t blame the majority for being scared of nuclear energy. The disasters at Chernobyl, and even the relatively recent one at Fukushima, are a grim reminder of the inherent dangers associated with the use of nuclear energy. Too many people at the time, these nuclear disasters highlighted the troubles that came with trying to “bend nature” to humanity’s will. Imagine the surprise researchers had when they found a completely natural nuclear reactor site in Western Africa, made by Mother Nature herself.

The possibility of an entirely natural nuclear reactor wasn’t all that unexpected. In 1956, Japanese physicist P. K. Kuroda first proposed that an all-natural nuclear reactor was, in fact, possible if given the right circumstances to exist. First, there needed to be a “critical mass” of uranium-235, the type of uranium that is widely used in today’s nuclear fission plant. This “critical mass” allows for the chain reaction of nuclear fission to start so that this process could grow large enough to sustain itself. Also, this process required the use of water, which would help to moderate the rate of nuclear fission at this point, so that the nuclear fission process could sustain itself over a long period, and not just use all of its resources at once and stop the rate of nuclear fission afterward. The water was needed to control these reactions so that the fission rate could remain controlled and steady over an extended period.

In 1972, French physicist Francis Perrin examined the uranium samples taken from Oklo, Gabon. These samples contained a significantly lower amount of uranium-235 than the typical uranium ore. At first, this discrepancy initially seemed to be just a coincidence, which followed the general depletion of heavy metals in the area. However, Perrin and his team soon realized that this depletion of uranium-235 was more than just a coincidence after they had compared the depleted uranium in Oklo to the surrounding uranium samples from neighboring uranium mines, which had the regular percentage of uranium-235. The discovery of unusual chemicals in these uranium samples, compounds which signaled that fission had indeed occurred. As a result, Perrin concluded that Oklo was, in fact, a 2-billion-year old natural nuclear reactor, which had operated for over thousands of years.

An illustration depicting the 16 natural nuclear reaction sites in Oklo

Even two billion years ago, Oklo had both an intense concentration of uranium and plentiful water sources, satisfying both of the requirements that Kuroda had proposed earlier. This combination allowed for Oklo to be the ideal location for a natural fission reactor. However, this combination of high uranium density coupled with plentiful water sources was not unique to Oklo. It was generally found throughout northwestern Africa. We still don’t know what makes Oklo unique from these other places or if Oklo is the only natural nuclear reactor found. Given that the natural nuclear reactor at Oklo was found only relatively recently, it is still very much possible that other natural nuclear reactors have been formed in Earth’s past, or even if there are still some natural nuclear reactors, we have yet to discover.

A seemingly unassuming picture of one of Oklo’s nuclear reactor sites

However, that’s not all.

Biological species have been on this earth for billions and billions of years. The earth is 4.5 billion years old, and for a vast majority of that period, life has been present on earth in one way or another, although for most of that time, life pretty much meant just simple prokaryotes. However, 2 billion years ago, something changed. This 2 billion year mark marked the first time life transitioned from simple prokaryotes into the much more complex eukaryotes. This “transition” into a more complex phase of life 2 billion years ago marked the rapid development and change of life itself from just unicellular species, to large and complex multicellular species, and ultimately to us humans billions of billions of years later.

Some of the thumb-sized eukaryotic fossils found in Gabon

The oldest of these complex eukaryotic species have been found in Oklo, just a few miles (and in most cases less) from the various “natural” nuclear reactor sites in Oklo. To a select group of researchers and me, the relationship cannot be any clearer. This significant step in the development of life took place 2 billion years ago in Oklo, at nearly the same time and place where the natural nuclear reactors started to run. I cannot say how and why these two events are related since no initiatives or studies focus on the link between these natural nuclear reactors and the development of eukaryotic life. There doesn’t seem to be one starting up any time soon. In the end, it may just be a big coincidence. I am not very qualified in the first place to be making such grand claims. That being said, I think this topic deserves to be looked into at depth by the higher minds of our age. Science, by its very nature, is interconnected. We find discoveries and revelations by connecting what we already know to find out something more, something new. At the worst, this study will prove to be irrelevant and a significant waste of money, the fate of an unfortunately large percentage of reviews in almost every field. However, if there does seem to be a connection between these two events, I know that this research will help bring about a greater insight on one of the most significant turning points in Earth’s biological history.