Imagine that two billion years ago the primary nuclear reactor was built not by humans, but by nature itself.
That's exactly what happened in 1972, when a team of French scientists analyzed a sample of uranium ore from a mine in Oklo, Gabon, and located that it contained a lower than usual amount of uranium-235.
Uranium-235 is an isotope that may undergo nuclear fission, which is the means of splitting atoms to release energy. Scientists realized that the one possible explanation for this anomaly was that the uranium ore was a part of a natural nuclear reactor that operated within the distant past.
“After further investigation, including on-site investigation, they found that the uranium ore had fissioned itself,” he added. he said Ludovic Ferrière, curator of the rock collection on the Natural History Museum in Vienna, where in 2019 a part of the interesting rock might be presented to the general public. “There was no other explanation.”
How did this natural nuclear reactor work? And what can we learn from this today?
The Oklo reactor was one in every of 17 natural reactors that were inbuilt the Gabon region about two billion years ago, when the concentration of uranium-235 within the Earth's crust was much higher than today.
The reactors were positioned in a sandstone layer containing wealthy deposits of uranium ore. The sandstone also acted as a natural groundwater filter, which played a key role in mitigating the nuclear response.
Water is moderator since it slows down the neutrons released during fission and increases the likelihood that they’ll cause further fission of other uranium atoms. This creates a series response that sustains the production of nuclear energy.
“Just like in an artificial light water nuclear reactor, the fission reactions, without anything to slow down the neutrons and moderate them, simply stop,” said Peter Woods, leader of the IAEA's uranium production team. “Water acted as a moderator in Oklo, absorbing neutrons and controlling the chain reaction.”
However, if the water level is just too high, it may also absorb too many neutrons and stop the response. This is strictly what happened at Okel, where the groundwater level modified over time, making a natural feedback mechanism that adjusted the reactor's power output.
The Oklo reactor operated intermittently for a whole lot of 1000’s of years, producing about 100 kilowatts of power, enough to light 1,000 light bulbs.
The reactor's power output varied with water levels and produced power pulses on average every three hours. The reactor also produced various radioactive byproducts resembling plutonium, neodymium, ruthenium, and xenon.
Some of those byproducts were used as evidence supporting the existence of a natural reactor because they corresponded to the expected fission products of uranium-235 fuel.
The Oklo reactor is just not only an incredible example of nature's ingenuity, but in addition a invaluable source of knowledge for contemporary nuclear science and engineering. One of crucial lessons we are able to learn from Oklo is the best way to store nuclear waste safely for the long run.
Radioactive byproducts from the natural reactor have been exceptionally well preserved in the unique ore deposits for 2 billion years, with minimal leakage or migration into the encircling environment. This shows that geological formations might be effective barriers separating nuclear waste from the biosphere.
Another lesson we are able to take from Oklo is the best way to design more efficient and sustainable nuclear reactors for the long run. The natural reactor had a really high fuel utilization rate, meaning it drew most of its energy from the uranium ore before it was exhausted.
The natural reactor also had a really low environmental impact since it produced no greenhouse gases or other pollutants. Moreover, the natural reactor had the power to self-regulate and self-stabilize, requiring no human intervention or control systems.
The Oklo reactor is a reminder that nature has been experimenting with nuclear energy long before us, and that we are able to profit from exploring its secrets and solutions.
Image Source: Pixabay.com
