Natural nuclear reactors

Paul Raven @ 27-10-2009

My magical statistics monkeys tell me that last week’s post on dissociative fugues was surprisingly popular, so I thought I’d share another article I found fascinating. Yet another hat-tip to Geoff Manaugh at BLDGBLOG for this one; it’s a Scientific American report on naturally occuring nuclear reactors. Yes, you read that right – nuclear power plants that just happened by geological chance.

More than two tons of this plutonium isotope were generated within the Oklo deposit. Although almost all this material, which has a 24,000-year halflife, has since disappeared (primarily through natural radioactive decay), some of the plutonium itself underwent fission, as attested by the presence of its characteristic fission products. The abundance of those lighter elements allowed scientists to deduce that fission reactions must have gone on for hundreds of thousands of years. From the amount of uranium 235 consumed, they calculated the total energy released, 15,000 megawatt-years, and from this and other evidence were able to work out the average power output, which was probably less than 100 kilowatts—say, enough to run a few dozen toasters.

(Or a few dozen highly-efficient computers, perhaps?)

It is truly amazing that more than a dozen natural reactors spontaneously sprang into existence and that they managed to maintain a modest power output for perhaps a few hundred millennia. Why is it that these parts of the deposit did not explode and destroy themselves right after nuclear chain reactions began? What mechanism provided the necessary self-regulation? Did these reactors run steadily or in fits and starts?

Go read the whole thing; the science isn’t too heavy, and it’s a pretty wild idea. I’m pretty sure I’ve read about something similar in a Stephen Baxter novel (though I can’t for the life of me remember which one); at the time I assumed he was speculating in a vacuum, but I guess I should have known better. 🙂

Regarding the popularity of the dissociative fugues post, I’ve been wondering whether perhaps I should be spending more time linking to interesting stuff and less time waffling around on tangents? It’s you guys who read this stuff, so what would you like to see here – more random points of interest, more speculative ramblings, or a blend of the two?

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5 Responses to “Natural nuclear reactors”

  1. Gerry Allen says:

    Mr. Raven:
    Just keep writing the sort of content you write now. After all, what is attractive about Futurismic is the content you provide. This is a long way of saying “Keep up the good work.”

    — Gerry M. Allen

  2. Chris says:

    Paul,
    Please keep blending! Your speculative ramblings are why I keep coming back. There’s data everywhere; I need intelligent nervous systems to parse it for me. Thanks for the hard work.

    Also of tangential interest, Stewart Brand had an interesting flip-flop on Nuclear, covered back in August on Edge.org. Provocative, I think.

    http://www.edge.org/documents/archive/edge298.html#brand

  3. docduke says:

    Briefly, “ditto.” You find interesting things, for which I do not find links anywhere else. My interests lie more in the solid science side (likt this article), but I almost always find your posts enlightening!

  4. Jesse says:

    The Baxter book was Manifold: Space or Manifold: Time (at least those were the American titles). And yes, more of this sort of article, please.

  5. Paul Raven says:

    Thanks for the kind words and feedback, folks – I’ll do my best to keep it up. 🙂