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Understanding the 2 Billion-Year-Old Natural Nuclear Reactor In W Africa 152

Posted by samzenpus
from the it's-getting-hot-in-here dept.
KentuckyFC (1144503) writes "In June 1972, nuclear scientists at the Pierrelatte uranium enrichment plant in south-east France noticed a strange deficit in the amount of uranium-235 they were processing. That's a serious problem in a uranium enrichment plant where every gram of fissionable material has to be carefully accounted for. The ensuing investigation found that the anomaly originated in the ore from the Oklo uranium mine in Gabon, which contained only 0.600% uranium-235 compared to 0.7202% for all other ore on the planet. It turned out that this ore was depleted because it had gone critical some 2 billion years earlier, creating a self-sustaining nuclear reaction that lasted for 300,000 years and using up the missing uranium-235 in the process. Since then, scientists have studied this natural reactor to better understand how buried nuclear waste spreads through the environment and also to discover whether the laws of physics that govern nuclear reactions may have changed in the 1.5 billion years since the reactor switched off. Now a review of the science that has come out of Oklo shows how important this work has become but also reveals that there is limited potential to gather more data. After an initial flurry of interest in Oklo, mining continued and the natural reactors--surely among the most extraordinary natural phenomena on the planet-- have all been mined out."
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Understanding the 2 Billion-Year-Old Natural Nuclear Reactor In W Africa

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  • by Noishkel (3464121) on Thursday May 01, 2014 @03:09AM (#46887191)

    Come on... who here doesn't think that this isn't the remains of a eons own star cruiser out there?

    Well okay, it probably isn't... but it would be cool if it was!

    • by Anonymous Coward

      Seeing things fly made us dream of the skies and eventually led to flight.
      Spider webs led to modern ballistic fibers.

      But this time, there was no such natural inspiration. We dreamed and created something we could not have conceived of have been standing on without ever noticing (well, not for long before an 'invisible curse' killed everyone anyways) not even two centuries ago. Only with functional, if crude, reactors operational did we come across their ancient burnt out forms.

      We made the atom ours, friend.

    • Were that true, there should be other evidence of the starship. Unless they were just disposing of spent fuel? Cool idea, right, since uranium is found naturally in nature and we could just dispose of it by making it as diluted in rock as it is in nature?

      Although that's an interesting idea for the disposal of nuclear (fission) waste for an advanced civilization, I tend to believe that the energy required to melt rock and integrate melted fuel rods to a dilute enough concentration not to harm natural life

      • In addition, any civilization THAT advanced would undoubtedly be able to get better efficiency out of their reactors before zipping away.

        My guess is they'd also be running reactors that could use the fuel up more or less completely, resulting in far less spent fuel being produced, if any.

        • by tlambert (566799)

          In addition, any civilization THAT advanced would undoubtedly be able to get better efficiency out of their reactors before zipping away.

          My guess is they'd also be running reactors that could use the fuel up more or less completely, resulting in far less spent fuel being produced, if any.

          You know, kind of like France does, with their spent fuel reprocessing and use of breeder reactors...

      • Re: (Score:2, Interesting)

        by Anonymous Coward

        The host rock for the Oklo reactors is fairly ordinary Proterozoic-aged sandstone and shales, so if some ancient civilization did abandon waste products, they basically left it on the surface on a beach or river bank about 1.7 billion years ago. It wasn't molten rock. Interestingly enough, there's also a lot of bitumen (solid oil) in the deposit, so there was plenty of organic material associated that was probably involved in trapping the uranium. Maybe a gigantic landfill? :-)

        • As usual, the guy saying "cost prohibitive" has absolutely no idea what he's talking about. Typical financier.

        • by RockDoctor (15477)

          The host rock for the Oklo reactors is fairly ordinary Proterozoic-aged sandstone and shales,

          Yeeees. Nothing particularly abnormal about the host rock.

          so if some ancient civilization did abandon waste products, they basically left it on the surface on a beach or river bank about 1.7 billion years ago.

          Noooo. Part of the point of the paper linked to (you did read TFP, didn't you? That's why the authors wrote it and posted it to Arxiv, for people to read.) was to describe a lutetium excite state thermometer wh

      • If your civilization is advanced enough to have inter-stellar starships, the simplest way of dumping a few tons of nuclear waste without having to worry about environmental impact would be to load the material in a rocket/torpedo and fire it at the most convenient star you come across.

      • by Agripa (139780)

        Although that's an interesting idea for the disposal of nuclear (fission) waste for an advanced civilization, I tend to believe that the energy required to melt rock and integrate melted fuel rods to a dilute enough concentration not to harm natural life would be cost prohibitive. In addition, any civilization THAT advanced would undoubtedly be able to get better efficiency out of their reactors before zipping away.

        I agree that they would have better things to do with the waste but they could bury it in a s

    • Come on... who here doesn't think that this isn't the remains of a eons own star cruiser out there?

      Well okay, it probably isn't... but it would be cool if it was!

      If I recall correctly Commander Adama set the fleet for a collision course with the sun, not the earth.

  • by SuperKendall (25149) on Thursday May 01, 2014 @03:11AM (#46887197)

    Except for the shallow one mentioned at the end of the article that still remains, just mostly washed out...

    It seems like the other aspects they wanted to study (like the spread of byproducts) is still feasible, since those would have spread beyond the mining site if they spread at all.

    • by Sockatume (732728)

      One of the useful early findings was that the reaction products hadn't appreciably migrated away from the original uranium seam, which is important for understanding waste disposal. Unfortunately that probably means that most of the useful information left with the uranium.

      • One of the useful early findings was that the reaction products hadn't appreciably migrated away from the original uranium seam

        Exactly, that's the primary interest on that front. Now they know that even over billions of years dangerous elements can stay put given the right geologic conditions.

        Unfortunately that probably means that most of the useful information left with the uranium.

        But some of it still remains in the shallow reactor, so they can find it if they think there's anything more of value to lear

        • by careysub (976506)

          ...

          Also now that they know is possible, they can probably find other areas where the same effect occurs. I think it's really unlikely that's the only place on earth the effect happened when it occurred naturally across several sites in the area.

          Such rich ore in thick veins is very rare - the uranium content of the ore was the highest in the world, 20-60% uranium, the average ore concentration current mined is around 1%, and many mines operate with ores containing a few tenths of a percent. Some Canadian mines have ore grades up to 20%, so there is a possibility it another might be found there.

          We do know that similar reactors have existed in the past. The isotopic concentration of U-235 in natural samples exhibits an unusual variation in concentra

    • "...to discover whether the laws of physics that govern nuclear reactions may have changed in the 1.5 billion years..."

        Laws of physics changed?

      What?

      • by MightyYar (622222)

        It's conceivable that some constants and such have a slight drift. Hell, space itself appears to be expanding so anything is fair game IMHO!

      • by ekgringo (693136)
        They're more guidelines, really.
      • by RockDoctor (15477)

        Laws of physics changed?

        What?

        To be more precise, by comparing the various decay product chains, they constrain the amount of change that could have happened in parameters such as the fine structure constant. Which is an effort the astronomers are making too, at the other end of the periodic table.

  • by Anonymous Coward

    Is there a non-tablet-friendly version of the article? One that's non-blinding on a normal screen?
    Sorry for trying to read it...

    • by rvw (755107)

      Is there a non-tablet-friendly version of the article? One that's non-blinding on a normal screen?
      Sorry for trying to read it...

      CTRL-A, open your text editor, CTRL-V

    • by pisces22 (819606)

      Is there a non-tablet-friendly version of the article? One that's non-blinding on a normal screen? Sorry for trying to read it...

      In Firefox: View -> Page Style -> No Style

    • by RockDoctor (15477)

      Is there a non-tablet-friendly version of the article?

      The paper cited is a standard PDF written to "Letter" size or "B4" (I can't tell the difference at a glance). Nothing blinding. I didn't waste time looking at the linked "science journalism" - why would you if you've got the paper to read?

  • by Anonymous Coward on Thursday May 01, 2014 @03:58AM (#46887265)

    What's the deal with these ads that pop up from the bottom on slashdot?

    Wasn't the "beta" experiment enough to piss people off with?

    They need to find new ways?

    • You need to familiarize yourself with browser plug-ins...

  • by tinkerton (199273) on Thursday May 01, 2014 @05:27AM (#46887451)

    also to discover whether the laws of physics that govern nuclear reactions may have changed in the 1.5 billion years since the reactor switched off.

    What bollocks. I think the actual question to ask is how it's possible to create the conditions for an very large (the size of the mine)and extremely low density (the concentration of natural ore) nuclear reactor.

    In the days the preference for civilian reactors was to develop further along the design of the compact high density submarine reactors. The nuclear industry never got over that. There are prototypes of large reactors with much lower power density. It's a natural question to ask how low enrichment and low density one can go.

    • by ssam (2723487)

      Some people believe that rates of radioactive decay have changed with time, to allow the isotopic abundances that we see to be consistent with a 6000 year old universe and in order to be able to discount any archaeological or palaeontological result they don't like. Showing that nuclear physics was the same 2 billion years ago is unlikely to change their minds.

    • by silentcoder (1241496) on Thursday May 01, 2014 @07:06AM (#46887757) Homepage

      >What bollocks. I think the actual question to ask is how it's possible to create the conditions for an very large (the size of the mine)and extremely low density (the concentration of natural ore) nuclear reactor.

      No bollocks involved - those laws depend on the fundamental constants. Scientists have speculated for decades about the possibility that these may have been slightly different in the distant past - and thus the laws of physics would not be exactly the same.

      This is quite controversial, mavericky science because it's very hard to test - but it's actually become less so in the past 20 years or so because some evidence from astronomy (in particular the cosmic background radiation) is suggesting that they may have been slightly different in the very early days of the universe.
      Oklo offers a chance to look more recently (on a universal scale) but still a long time ago - 2 billion years, about half the lifetime of the planet.

      If there had been subtle and slight changes over the years - then 2 billion years ago should be enough to detect some - much smaller even than what cosmic radiation data has hinted at, but on the same line (that said there are other theories that could explain the radiation data - the question is unanswered at the moment since none of them have any other supporting evidence yet either).

      Now there's no proof the fundamental constants have changed at all since the big bang, but there's no proof they haven't. For most physics it's perfectly adequate to assume they have always been constant, but if they weren't and we could determine that, it would change a lot of our understanding of physics - particularly the physics of the early universe.
      By factoring in those different values we could possibly explain a lot of the other things which currently remain open questions.

      So while it's unlikely - it's nevertheless and most decidedly NOT bollocks. It's maverick science for sure - but it's still science and still done according to the scientific method. If it yields results those results will be greatly valuable.
      Just because there's a 99.999% chance your theory is a dead end, doesn't mean it's not proper science to damn well test it and make sure.

      • by tinkerton (199273)

        I'm not saying researching the possibility that universal constants are not constant is bollocks, though I'd consider it too speculative for science. But once one starts taking an open environment 'dirty' testcase where the ratio 235/238 is different from the sample nextdoor as a clue for variable universal constants, then one is really in the middle of bollocks territory.

        • by Sockatume (732728)

          It really isn't. I'm no nuclear physicist but it seems that the reaction cross-sections change so dramatically with respect to the fine structure constant, that seeing these fission reactions at all puts a very strong bound on how the fine structure constant could have varied.

          • by tinkerton (199273)

            Well I asked for that. I should have said it differently. Another try: there is a lot of experimental evidence to show that the fine structure constant is constant. If it hadn't been constant we would have known. With the claim that the fine structure constant is a real constant one is on solid ground.

            Then the possibility that outside of the solid experimental proof the constant could still vary "maybe the constant was not always the same" - should be handled very sparingly. It's an idea to be kept on a sho

            • People should not start trotting out a 'variable constant' hypothesis because some ratio of elements is wrong in ore.
              The wrongness in the ore did not challange them to consider some old constants in fact may vary (you seem not to believe that this in deed a long open question in physics. However: it is!). The wrongness lead them to that particular mine and with test data going back roughly 2billion years, they figured that could be a good hunting ground. Thats all.

            • by idontgno (624372)

              People should not start trotting out a 'variable constant' hypothesis because some ratio of elements is wrong in ore.

              Nonetheless:

              The most exciting phrase to hear in science, the one that heralds new discoveries, is not 'Eureka!' but 'That's funny...'

              -- Isaac Asimov

            • by cusco (717999)

              No, the OPERA group was right. They said, "We have this result, which makes no sense. We've looked at A, B, C, D and E, and still get the same results. We've recalibrated F, G and H multiple times and it makes no difference. We've replaced I and J, but the equipment seems fine. Anyone got any ideas?" When you think you've done everything right and still get surprising results it's time to let others know, not time to hide the evidence. Do that and every piece of research you do in the future is taint

            • by Sockatume (732728)

              The ratio wasn't wrong. The research was provoked as a way of quantifying the possible variability given that it appears constant.

        • by Sockatume (732728)

          ...and for that it's worth, the research takes into account site-to-site variability in the composition and the subsequent behaviour of the reactor.

        • by ceoyoyo (59147)

          As opposed to one of the best available alternate methods for determining universal constants, astronomy?

          Physicists and chemists are aware of how to use statistics to make good estimates in the presence of heterogeneity.

        • by Altus (1034)

          its not about the sample next door, its about every single sample from the giant cloud of debris from which our solar system formed. The fact that its all the same throughout the world (when it hasn't undergone spontaneous fission is part of the reason we know how old the rock we are standing on is.

        • by RockDoctor (15477)

          where the ratio 235/238 is different from the sample nextdoor as a clue for variable universal constants, then one is really in the middle of bollocks territory.

          I'd suggest that you read the Arxiv paper, and find out what the actual researchers are saying, not what "science journalists" are saying.

      • There was a really great science fiction book I read that dealt with that. I thought it was by Alastair Reynolds, but looking over his bibliography I didn't see anything that fit the description. Essentially it's one of those "we've found ancient alien shit, scientists go explore it and discover THE TERRIBLE SECRET OF SPACE!" books. In it, a rogue planet is discovered in interstellar space with an ancient alien city/mechanism. None of the technology works right, or makes any sense from our understanding of

        • Isaac Asimov's The Gods Themselves deals with something similar - a parallel universe where the values of some of the universal constants are slightly different from the values in our universe.
      • Scientists have speculated for decades about the possibility that these may have been slightly different in the distant past - and thus the laws of physics would not be exactly the same.

        This is quite controversial, mavericky science because it's very hard to test -

        If it's not testable, then by definition it is not science.

        Now there's no proof the fundamental constants have changed at all since the big bang, but there's no proof they haven't... By factoring in those different values we could possibly explain a lot of the other things which currently remain open questions.

        So while it's unlikely - it's nevertheless and most decidedly NOT bollocks.

        Then it's not science.

        It's maverick science for sure

        "Maverick Science". Made up definitions still don't get you to a testable theory.

        • This is quite controversial, mavericky science because it's very hard to test -

          If it's not testable, then by definition it is not science.

          hard to test != untestable

        • >If it's not testable, then by definition it is not science.

          I said it's HARD to test, I didn't say it's impossible.
          The REASON it's hard to test is because it's a theory about what may have happened billions of years ago - and billion year old samples are kind of rare. The big bang theory was hard to test for the same reasons and took decades to become accepted - back in the 1960's it was laughed of as glorified creationism.

          The whole point is to test the theory because this IS a 2 billion year old sample.

      • Now there's no proof the fundamental constants have changed at all since the big bang, but there's no proof they haven't.

        Yes, there is. Astronomers are peering into the past every time they look through their telescopes--often the very distant past. They don't see anything that indicates that the laws of physics are changing.

    • by Sockatume (732728)

      No, it's not bollocks, it's actually a nice demonstration that the fine structure constant is actually constant. It's worth emphasising that even given the size of the mine, its power output was only about 100kW.

      • i don't know what fine structure constant means. my office has solar panels and we produce 30kw, so I don't think 100kw is a lot. also, any miner will tell you that it is hot underground, indicating these reactions are more common than you think (when the nuclear reaction happens it creates lots of heat).
        • by Jmc23 (2353706)
          Put several people in an enclosed insulated space and see how hot they get.

          It's mostly cold there, which is why cheap geothermal can work.

    • by Zorpheus (857617)

      What bollocks. I think the actual question to ask is how it's possible to create the conditions for an very large (the size of the mine)and extremely low density (the concentration of natural ore) nuclear reactor.

      In the days the preference for civilian reactors was to develop further along the design of the compact high density submarine reactors. The nuclear industry never got over that. There are prototypes of large reactors with much lower power density. It's a natural question to ask how low enrichment and low density one can go.

      2 billion years ago the concentration of U-235 was still 3% of the uranium. It decreased due to the shorter half-lifes of U-235.
      A pressurized heave water reactor runs with today's unenriched uranium, so we are better than that already.

    • by RockDoctor (15477)

      an very large (the size of the mine)and extremely low density (the concentration of natural ore) nuclear reactor.

      The actual reactor zones are much smaller than the mine. Only a few tens of metres across for some of them. The mine as a whole contained 14 to 17 reactor zones (counts vary) at different levels in the mine from near-surface to deep underground. Now that the mine has been mined out, there's just the one un-mined example at a mine 30-odd kilometres away. And that mine has been shut down for a coup

  • We're just some alien's toilet.
  • "to discover whether the laws of physics...may have changed"
    No.
    • That's a legit question over great lengths of space and time.

    • by Jmc23 (2353706)
      ah, a science fanboi who doesn't realize just how many theories deal with changing constants.

      If you want absolutes, religion is on the left.

  • "After an initial flurry of interest in Oklo, mining continued and the natural reactors--surely among the most extraordinary natural phenomena on the planet-- have all been mined out."

    That this story is 42 years late?
  • It says the reactor powered on two billion years ago, that is 2,000 million years ago, then it says that it ran for 300,000 years, that is 0.3 million years. Then it says that it has been powered off for 1,5 billion years ago (1,500 million years ago). If it was powered for less than a million years, why do the numbers disagree by 500 million years?
  • How much heat could such a natural reactor generate? Would it be enough to affect local climate? Ocean currents and/or temperatures?
    • Depends on how local you are referring to. A poster further up mentioned that it probably put out about about 100kw or about the same power as a small car. While cool I would probably put it in the same category as the natural laser on Mars [harvard.edu] as just an interesting natural phenomenon that won't affect me.
  • Careful... (Score:5, Funny)

    by Mayhem178 (920970) on Thursday May 01, 2014 @11:46AM (#46889467)
    Don't let the hippies hear you suggest that fission is a naturally occurring process. They might...

    *sunglasses*

    ...go nuclear.
  • Given TFS later tells of "1.5 billion years since switching off", and the impossibility of measuring 300.000 years accurately in this context, I suppose the reactor was active for 300 million years, not 300 thousand years. Is ee the "300000" number is in TFA, but it looks suspect.

If A = B and B = C, then A = C, except where void or prohibited by law. -- Roy Santoro

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