I like the Oklo story.

The rumour I heard some years ago was that the phenomina was "Discovererd" when the people the yellowcake was eventually sold to came back to the mining company and said "Oi, This stuffs second hand!" Whether this is true or not I dont know, but it makes a nice story!

I also understand that analysis on the reactors indicates that the fission products, despite being in an open and wet enviroment, never migrated more than a couple of meters from the active cores-so much for the need to bury "waste" in concrete lined bunkers deep underground in order to "protect the enviroment" Of course the Sci Fi part of me likes to think that Oklo was the origen of life on earth (but, of course, we all know that life arrived on comets! )

Dusty