Are there any more "OKLO's?

["Dr. Marvin Goldman" <mgoldman@ucdavis.edu>]

Some 25 years ago reports were published on a "natural reactor" which
fissioned high content uranium ore some 2 billion years ago in Gabon,
Africa.  The geologic sleuthing was a fascinating story and showed that the
plutonium (and its decay products), which was naturally produced over
several centuries of spontaneous fissioning of U-235, did not migrate far
from the original ore seam.  The U-235 concentration back then was about
3-4%, not the 0.7 % U-235 of today's ore, and thus needed just some neutron
moderation from water to spontaneously fission.  I think it was all
summarized in a Scientific American article in about 1979.

My question is whether any of you  knows of other locations on earth
besides OKLO where this "natrual reaction" took place.  What are the odds
that only one uranium ore body on our planet underwent this action?   With
all the debate about high and low level radioactive waste disposal, and the
accompanying long term scenarios about  real and imagined consequences,
OKLO provides a valuable and interesting case study and object lesson.  But
are there any other lessons like it out there?  I'd appreciate your help on
this.

Marvin Goldman
mgoldman@ucdavis.edu