Oklo natural nuclear fission reactor
GeologyComments
I am skeptical of the timeline regarding the nuclei. Estimates for early eukaryotes are often pushed back to 2.1 billion years, which puts them right in the middle of the Oklo activity.
This is basically a case study in groundwater management. The reaction only happened because water acted as a moderator, which is the same reason we are so obsessed with aquifer stability around modern waste sites.
It is encouraging that the natural clay minerals in the surrounding rock acted as a seal. They kept the radioactive isotopes from migrating far, even over billions of years.
If the water was the primary moderator, wouldn't that suggest these events happen more frequently than we have documented? Perhaps we have been looking for reactors that mirror human design instead of random geological accidents.