THE world's last untouched natural nuclear fission 'reactor' is in the centre of a row between conservationists and a mining company. The reactor was formed naturally two billion years ago, VIken deposits of high-grade uranium ore went critical in what is now Gabon, in western Africa. A group of European scientists is trying to stop the company from digging up the site.

There are 15 such reactors in the region and only one of them has escaped mining. The only intact prehistoric nuclear waste site contains "fission products very similar to spent fuel from modern reactors," says Francois Gauthier-Lafaye of the Centre for Surface Geochernistry in Strasb@urg, France, who is leading the campaign to save the reactor. For the,@Kientists, it provides an opportunity to observe how buried uranium isotopes and fission products behave. The French government has, on behalf of the scie*mists, reached an agreement with French-Gabonese mining compaliy COMUF to postpone work at the intact reactor at Bafigombe in the Franceville basin. The deposit contains 100 to 200 tonnes of uranium buried 10 metres below the surface.

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