Near the provincial capital, Franceville in Gabun sits a nuclear fission reactor. Unlike many nuclear energies in West Africa, this particular reactor has not been commissioned by the US government. It is naturally occurring.
The area was slid under the nose of interest when an abnormally small amount of Uranium-235 was found in the surrounding soils. In the average geology of such an area, the percentage content of such an isotope is usually around 0.72% with little global variation. The findings for the isotope however were 0.6% - inconsistent with any other radioactive isotopes of such a lithology.
Subsequently, there was a hive of interest in analysing other radioactive samples from the geology. Scientists analysed Neodymium and Ruthenium isotopes finding that compared to the normal 27% Neodymium-123, Oklo had only 6% but had an evidently higher percentage of Neodymium-124. Similarly, with Ruthenium-99 they found a significantly higher percentage occurring within the environment, explained by TC-99 decay into Ru-99 which is a nuclear decay process releasing gamma radiation. The only explanation for this sequence of anomalies is continuous fission events occurring. Scientists predicted that such events are likely to have started around 2 billion years before discovery.
This reactor had formed when a uranium-rich mineral deposit became inundated with groundwater, acting as a neutron moderator, as do the carbon control rods used in power stations. A nuclear chain reaction, therefore, took place. With the heat generated from the fission, the groundwater gradually simmered away, slowing the reaction. Following a period of cooling, the water table crept its way into the same groundwater reserve, slowly restarting the reaction, completing a full cycle every three hours.
This reaction cycle is proposed to have continued for hundreds of thousands of years and ended when the ever-decreasing fissile materials no longer could sustain a chain reaction. Uranium fission normally produces five most common gas isotopes, all of which had been found below the reactor, a discovery to really get gassed about.
After the discovery of this first reactor, a series of 6 other reactors on the same inter-geological plane was found – an almost alien discovery that shook the scientific world. A nuclear reactor, 1 billion dollars cheaper than the usual, formed with nothing but rock and heat, the most abundant materials found on this planet.
A key factor as to why the Uranium core finally went critical around 1.3 billion years ago was due to the fact that the fissile isotope U-235 made up around 3.7 percent of all of the uranium found, while the other percentage was made up by non-fissile U-238 which has a much longer half-life than the fissile isotope, hence today our percentage of U-235, owing to decay has dropped to around 0.7 percent. Such a nuclear reactor therefore would not be able to form in today’s conditions without heavy water or dense graphite.
Another barrier to our modern natural nuclear reactors is the oxygen holocaust that deprived the earth of oxygen before once again increasing the supply. It was this increase that allowed the U-235 to dissolve in the groundwater hence produce a large enough concentration for a nuclear core to form at Oklo.
The rock samples that were found at Oklo, some of them recovered during drilling campaigns are stored in the headquarters of France’s nuclear power and renewable energy company Orano. The samples were then donated to Vienna’s museum of Natural history made possible by the Atomic energy commission in France with the support of the French permanent mission to the United Nations and the International Organizations in Vienna, a huge strive for scientific explorations by the UN. With 750,000 visitors a year, the sample will serve homage to the reality of harmless radiation around us, in our food, water, air, and our bodies. But with its preservation and mothering of all man-made nuclear reactors, it also serves as a well-deserved warning to reactors preceding it, one of control, regulation and safety, an educator to the masses.
Why is this ancient nuclear reactor helpful to us? Well, recent findings suggest that the non-volatile fission products only moved centimetres in the uranium veins within the rock over the last two billion years which could offer a natural analogue for nuclear waste disposal, preventing the contamination of groundwater for animals and for ourselves, much of which is linked to gastric and oesophageal cancers.
The radioactive waste of Oklo was held under its granite, sandstone stomach immersed in clays surrounding the reactor’s areas resulting in no cross-contamination of non-reactor contained water supplies. By analysing the remnants of these nuclear reactors and understanding how underground rock formations contain the waste, the scientists studying Oklo can apply their findings to containing nuclear waste today. But why stop at nuclear waste, with such as large self-contained geologically hardened area, the waste deposit could be harnessed for plastics, preventing microplastics causing liver and gastric cancers and even for toxic electrical waste preventing the oesophageal cancers and child deformations found near Olusosun waste deposit where much electrical waste had been left.
This nuclear core begs the respect that heaven and earth had to be moved 2 billion years ago just to form the right sedimentary and metamorphic processes for a natural nuclear reactor to form. Today, we can spend 2 billion dollars to build one ourselves, with the side effect being occasional nuclear accidents. What can we learn from our geomorphological processes to regulate our energy production, to make our nuclear reactors safer and less prone to cyclic irregularities? Perhaps this is down to the enormity of energy demands, but shouldn’t we be working to leave nuclear power plants at consistent productivity to manage the safety of our environment and people rather than fluctuating its outputs.
Our Oklo nuclear cores draw closer and closer attention to what ‘green’ self-made energies can be harnessed without the need for jeopardization, coercion, or economic disruption. Should the UN be focusing more on scientific investigations into energy production beneath our feet rather than acrylic dollars and silicone aid to make our world go round?
Written by Lilly Horvath-Makkos
Artwork by Zara Masood
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