Re: Are there any more "OKLO's?

[muckerheide@mediaone.net]

Dr. Marvin Goldman wrote:
> 
> 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

Marvin, from an ANS email list in May:

> Many of you may have seen this article in Science, May 16, 1997.  
> 
> Natural Fission Reactor Threatened by Mining
> 
> In the west African jungle lie pockets of rich uranium ore that 2
> billion
> years ago burned like huge nuclear reactors.  But the last know rare
> deposit of this type - considered a natural analog of a nuclear waste
> repository - is slated to be mined next fall, say scientists who are 
> lobbying to save it.
>         The natural reactors were discovered in 1972 when scientists
> noticed that
> the ratio of the isotope uranium 235 (U-235) to U-238 in some ore
> samples
> from a Gabon mine in the Oklo area was surprisingly low.  Studies
> revealed
> that the U-235 had been consumed by fission due to an unusual set of
> conditions, including the presence of water, which moderated the
> reaction.
>         A French-Gabonese company called COMUF soon plans to mine the
> last of the
> 14 Oklo reactors.  But a team of European scientists who have been
> tracking
> radionuclides in the soil and water nearby are trying to save one
> site.  Led
> by Francois Gauthier-Lafaye of the Centre de Geochimie de la Surface -
> CNRS in Strasbourg, the researchers hope to spare a small undisturbed
> reactor in Bangombe, 30 kilometers from Oklo.  To succeed, however, the
> scientists must
> persuade the French government to pay COMUF for the 150 to 200 tons of
> uranium there, worth about $3.5 million, Gauthier-Lafaye says.
>         For now the French government plans to ask COMUP to delay
> mining the site,
> accord to Bernard Bigot, director-general of research and technology
> in France's ministry of research and education.  But the final decision
> will depend on a review of the reactor's scientific value, he says.
> Gauthier-Lafaye believes that "a little bit of pressure (from the)
> international science community" might also help.  To comment write to
> gauthier@illite.u-strasbg.fr.