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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 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 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 Anonymous Coward on Thursday May 01, 2014 @05:45AM (#46887515)

    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? :-)

  • 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.

The test of intelligent tinkering is to save all the parts. -- Aldo Leopold

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