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?

  • $\begingroup$ Don't you think either a minxy little kilowatt output, or a single example in more than a billion years would rule out any idea of a fission reactor forming naturally being in any way meaningful, let alone useful? $\endgroup$ Commented Feb 16, 2022 at 23:02
  • $\begingroup$ Well, no. Sixteen natural nuclear reactors were discovered in uranium mines at Oklo. An additional seventeenth natural nuclear reactor was also discovered at Bangombé, located about 30 km to the southeast of Oklo. $\endgroup$
    – Vogon Poet
    Commented Feb 17, 2022 at 14:58
  • $\begingroup$ Really? If you'd mentioned them before, wouldn't a kilowatt still be insignificant? Still, what differences d'you see between Cigar Lake and Oklo? $\endgroup$ Commented Feb 18, 2022 at 1:03
  • $\begingroup$ Is this conversation doing anything at all? What is wrong with the question please? $\endgroup$
    – Vogon Poet
    Commented Feb 18, 2022 at 1:05
  • $\begingroup$ In my view, nothing here suggests a fission reactor naturally formed at Cigar Lake, or anywhere else, could matter any more than what's been achieved in umpty labs. Based on circumstance and size, how could it help? $\endgroup$ Commented Feb 18, 2022 at 21:44

1 Answer 1


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.

There are no open pits at Cigar Lake,

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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.

  • $\begingroup$ The carbon deposit posited in the question is a bit of a red herring. It was water rather than carbon that served as a moderator in the Oklo natural reactor. $\endgroup$ Commented Feb 17, 2022 at 4:22

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