This Is a Natural Nuclear Reactor

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Two billion years ago, planet Earth had natural nuclear fission reactors, burning inside its crust. You are looking at the remains of one of them, located in Oklo, Gabon.

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These reactors are thought to have happened by natural causes, as a result of the abundance and density of Uranium-235—a natural fissile uranium isotope present in our planet and throughout the Solar System. Two billion years ago, there were 3,000 atoms of U-235 per 100,000 atoms of other materials.

In addition to having at least 1% of U-235 and be big enough to sustain the reaction, these natural nuclear furnaces required to have a low concentration of neutron absorbers (like Cadmium) and a high concentration of a moderator material (like water or Carbon). Nowadays there are no natural reactors happening on Earth because there are not enough quantities of this material.

These natural reactors are important to understand the formation of Earth, but also as a way to find new ways for natural radioactive waste containment. [Oklo via APOD]

DISCUSSION

By
RedEyeNinja

From the Oklo site:

"If a runaway reaction does take place a nuclear explosion can occur – but this did not take place at Oklo where the reactions were also self regulated."

This means that there were some natural fission reactors that were not self-regulated and caused nuclear explosions?

Would this also suggest that some sites could've been "special" places? ...maybe significant religious and ceremonial sites for ancient peoples...but no longer radiate as strongly as they did, say, 50,000 yrs ago?

It also seems that if these sites, self-regulated or not, could be huge source local radiation and a cause for genetic mutations long after they have extinguished...