Small localized deposits of 60%wt Uranium were found in Cigar Lake, Canada during the ‘90’s. If an exposed rich deposit like this were covered by sedimentary carbon from eroding rock, layering graphite on the uranium, would a fission reactor form naturally? Could it generate power in the kilowatt range as the Oklo reactor is thought to have done?
Given that the Cigar Lake uranium deposit is already buried beep, at 450 m below the surface, a "sedimentary carbon" deposit will not be deposited anywhere close to the uranium deposit. The age of the deposit is estimated to be 1.3 Ga (billion years).
Due to natural containment and lack of any traces of radioactive elements on the surface, the deposit is used as an example of an effective natural deep geological repository.
Infrastructure at the site includes an underground mine; freezing plants and associated freeze pads; ore processing and load out; water treatment; mine rock storage pads; temporary waste storage; warehouses; worker camp; and office and administrative buildings.
Also, given the relatively flat topography of northern Saskatchewan, where Cigar Lake is located, carbon sediments are unlikely to be deposited at anywhere near the uranium deposit and mine.