The title of this video might at first seem absurd, as humans were not on the planet approximately
2 billion years ago.
Yet, it IS accurate and there truly was an ancient nuclear reactor in what is now Gabon.
First, some clarification.
When people think of nuclear reactors, they tend to picture the wide cooling towers associated
with a man made power plant.
In contrast, the ancient nuclear reactor I am referring to originated due to a combination
of factors related to an incredibly high grade uranium deposit.
This dense deposit contained all of the factors necessary for and did produce a nuclear chain
reaction for more than 100,000 years.
This video will discuss this fascinating deposit, and mention how it sustained a natural nuclear
reaction 1.7 billion years ago.
The aforementioned natural uranium nuclear reactor is located in the nation of Gabon,
which is a country located on the west coast of central Africa.
It was located at the Oklo Mine in the eastern half of the country, which is 50 kilometers
northeast of the city of Franceville.
It’s discovery occurred in 1972, when French scientists were analyzing uranium hexafluoride
samples.
One of the routine tests checked for the levels of various isotopes of uranium present.
During this analysis, they found a large discrepancy.
The U235 levels should have been 0.72% but instead they were 0.60%.
This may not sound like a big deal, but this potentially implied that large quantities
of U235 was being smuggled off site since it was missing.
Thus, an investigation was triggered.
Strangely, this investigation confirmed that these readings were accurate but couldn’t
find any missing uranium as all of the proper procedures had been followed.
U235 was clearly missing, but no one had taken it.
The answer to this predicament came when a similar analysis was run on the uranium ore
samples within the Oklo Mine.
In certain sections of this mine, U235 concentrations were as low as 0.44%.
This meant that undisturbed wall rock in the mine had at one point bled this isotope of
uranium during an ancient natural process.
On Earth, we know of one thing that naturally causes the loss of U235, a nuclear reactor.
Further investigations showed that isotopes of the elements neodymium and ruthenium in
the uranium ore were a near perfect match for spent products at commercial nuclear reactors.
Thus, this ore looked like spent nuclear reactor material as that was exactly what it was.
So, how did this reactor work?
1.7 billion years ago, there was a highly dense natural layer of dark uranium ore in
the ground.
It was primarily a black color as it’s main component was a radioactive mineral called
uraninite.
This deposit was regularly filled with groundwater, which acted as a natural neutron moderator.
When this occurred, the radioactive decay of the deposit generated a sustained nuclear
reaction.
U235 fissioned during this reaction, which lasted approximately 30 minutes.
The vast amount of heat generated by this reaction caused the present groundwater to
boil away, thus stopping the reaction.
For the next 2.5 hours, the deposit cooled.
Once it had reached a low enough temperature, water filled back in this area, and the reaction
repeated itself.
This 3 hour cycle continued for several hundreds of thousands of years until too much U235
was spent to produce another sustained nuclear reaction.
So, how much power did this reaction produce?
During criticality phases, the oklo natural nuclear reactor produced about 100 KW of thermal
energy.
Of course, this wasn’t harnessed by anyone as humans were not around.
If it was to have been harnessed, it would be sufficient enough to power approximately
1,000 commercial light bulbs.
Since this discovery, other ancient small natural nuclear reactors were found in the
region the Oklo Mine.
No other sections of the planet outside of Gabon have revealed the presence of other
natural nuclear reactors.
I hope that you enjoyed this video.
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