Just read an interesting article about a natural, self-sustaining nuclear reaction that occured here on Earth...........

[RussellCattle]

........1.7 billion years ago. The article describes a site in Africa where naturally occurring Uranium, water, oxygen and algae came together in the right geological formation to start a nuclear reaction that switched on and off for 150,000 years. The author then goes on to use this historical fact to bolster his support for nuclear power today as a safer alternative to fossil fuels. Anyone here familiar with our DU friend "NNadir" will probably find this last bit also rather familiar, as he also advocates for nuclear power plants as safe and sane alternatives to our planet killing ways.

https://www.sciencehistory.org/stories/disappearing-pod/the-worlds-only-natural-nuclear-reactor/

(NN - my apologies if I've got this wrong.)

[Think. Again.]

1. We're going to need all the non-CO2 emitting energy tech we have..

...and that includes nuclear, until we can build out even safer sources to fill our energy needs.

And what no one REALLY wants to talk about, is how we are going to reduce our unneccesary energy consumption.

And that WILL happen, either by our own initiative and design, or as a result of the catastrophic effects of climate chaos that we are continuing to encourage.

[Eugene]

2. The Gabon natural nuclear reactor was included a university course aimed at the government and

geology majors covering world resource policy.

I remember at least of those same professors taught that there was less
danger from radiation under the shielded vessel of a reactor than
in the outside world. Early 1980s.

[RussellCattle]

3. An even better compaison of the relative dangers from radiation than the articles mention of kitty litter.

[NNadir]

4. Thank you. You have it right. I've written about Oklo many times, here and elsewhere.

I would link some of multiple writings on this topic, but it appears Journals are off line for maintenance.

Oklo has been studied for a long time as an indicator of the migration of fission products in uncontrolled circumstances, which involved water flows through the reactor cores in porous sandstone. It is known that most did not migrate very far, with some exceptions, notably technetium, which migrated as the soluble TcO₄^- ion, all of which has decayed to ruthenium. Even this did not migrate more than a few kilometers. (The Oklo formations show isotopic distributions for ruthenium reflecting this property, with the ⁹⁹Ru isotope being separated from the other fission product ruthenium isotopes.)

The cyclic behavior was tied to thermal feedback loops which is the primary control in human made thermal reactors, technically called "a negative void coefficient." Basically when water boils it can no longer moderate neutrons as well as when it is in the liquid state.

Ancient uranium was what we would now call "Low Enriched Uranium" because much of the shorter lived ²³⁵U (t_1/2 = 700 million years) had not decayed as much as it has now. Billions of years ago the fraction of ²³⁵U was on the order of between 3% and 4%. The migration of uranium became possible with the emergence of oxygen in the planet atmosphere.

A current case wherein we can follow the migration of fission products and actinides are the Hanford Reservation in Washington State, where the plutonium for American Nuclear Weapons was manufactured, as well as the Nevada National "Security" Reservation where nuclear weapons were tested underground.

I do have access to one post of mine on the migration of actinides at that site, as well as at Hanford, that I've written here, in which Oklo is mentioned with references: 828 Underground Nuclear Tests, Plutonium Migration in Nevada, Dunning, Kruger, Strawmen, and Tunnels

That (rather long and desultory) post contains reference to some scientific papers on Oklo.

Thanks again for your kind note.

[eppur_se_muova]

5. Scientific American published an article on this back in the 70's (my high school years) ...

https://www.scientificamerican.com/issue/sa/1976/07-01/

Apparently accessible if you register.