The Workings of an Ancient Nuclear Reactor – Scientific American

In May 1972 a worker at a nuclear fuel–processing plant in France noticed something suspicious. He had been conducting a routine analysis of uranium derived from a seemingly ordinary source of ore. As is the case with all natural uranium, the material under study contained three isotopes— that is to say, three forms with differing atomic masses: uranium 238, the most abundant variety; uranium 234, the rarest; and uranium 235, the isotope that is coveted because it can sustain a nuclear chain reaction. Elsewhere in the earth’s crust, on the moon and even in meteorites, uranium 235 atoms make up 0.720 percent of the total. But in these samples, which came from the Oklo deposit in Gabon (a former French colony in west equatorial Africa), uranium 235 constituted just 0.717 percent. That tiny discrepancy was enough to alert French scientists that something strange had happened. Further analyses showed that ore from at least one part of the mine was far short on uranium 235: some 200 kilograms appeared to be missing— enough to make half a dozen or so nuclear bombs.

via The Workings of an Ancient Nuclear Reactor – Scientific American.

Well, this is pretty fascinating. It’s old, but it’s new to me. Jeff, any other nukes familiar with this?

7 thoughts on “The Workings of an Ancient Nuclear Reactor – Scientific American”

  1. Yeah, I read about it when it was originality written up in SciAm…though 2005 seems a bit late for that.

  2. Read about it back in the 90’s. Gaia was doing nuclear long before Greenpeace-precursors ever stumbled out of the Rift Valley.

    1. I wonder if you could get a Greenpeace droid to segfault by asking him if natural things were good, then pointing this out when he said “yes.”

  3. This was making the rounds at the Navy’s nuke school in Vallejo back in the mid-70’s. Water flows in, moderates the neutrons, allows fission, fission heats up the water, water boils, no more water to moderate neutrons, no more fission, rocks cool down, water flows in, … Repeating cycle. Actually, a good demonstration of the value of a negative alpha-T.

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