Oklo fossil reactors

Another link that google turned up

http://www.alamut.com/proj/98/nuclearGarden/bookTexts/Lovelock_Oklo.ht
ml
Excerpt from James LoveLock: The Ages of Gaia (1988)
A bizarre consequence of the appearance of oxygen was the advent the
world's first nuclear reactors. Nuclear power from its inception has
rarely been described publicly except in hyperbole. The impression
has been given that to design and construct a nuclear reactor is a
feat unique to physical science and engineering creativity.
It is chastening to find that, in the Proterozoic, an unassertive
community of modest bacteria built a set of nuclear reactors that ran
for millions of years.
...
In the place that is now Oklo such a stream flowed into an algal mat
that included microorganisms with a strange capacity to collect and
concentrate uranium specifically.
...
Bacteria could not have debated the costs and benefits of nuclear
power. The fact that the reactors ran so long and that there was more
than one of them suggests that replenishment must have occured and
that the radiation and nuclear waste from the reactor was not a
deterrent to that ancient bacterial ecosystem. (The distribution of
stable fission products around the reactor site is also valuable
evidence to suggest that the problems of nuclear waste disposal now
are nowhere near so difficult and dangerous as the feverish
pronouncements of the antinuclear movement would suggest.)
The Oklo reactors are a splendid example of geophysical homeostasis.