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The first nuclear reactor was in Africa.... a long, long time ago
March 20, 2011 10:43 PM   Subscribe

The first nuclear reactor was in Africa, 2 billion years ago. Two billion years ago, there was enough uranium 235 in a naturally occurring deposit in Africa to fuel a nuclear fission reaction. In 16 separate locations, spontaneously occurring fission reactions went on for some hundreds of thousands of years, cycling multiple times per day. A picture of Fossil Reactor 15. The American Nuclear Society info site.
posted by bq (46 comments total) 47 users marked this as a favorite

 
I once read that the complex machinery of nuclear reactors is, for the most part, not at all about making a nuclear reaction happen; it's about making that reaction safe. The story reminds me a bit of the story of the demon core, a rather frightening anecdote from before scientists had a clear grasp of nuclear reactions.

From that link:

[The test] required the operator to place two half-spheres of beryllium (a neutron reflector) around the core to be tested and manually lower the top reflector over the core via a thumb hole on the top.

Allowing them to close completely would result in the instantaneous formation of a critical mass and a lethal power excursion, and the only thing preventing this was the blade of a standard flathead screwdriver manipulated by the scientist's other hand.

While lowering the top reflector, Slotin's screwdriver slipped a fraction of an inch, allowing the top reflector to fall into place around the core. Instantly there was a flash of blue light and a wave of heat across Slotin's skin; the core had become supercritical, releasing a massive burst of neutron radiation.

Freaky stuff, and good links.
posted by Rinku at 10:59 PM on March 20, 2011 [4 favorites]


Wikipedia actually has a rather nice article on this subject: Natural nuclear fission reactor.
posted by RichardP at 11:16 PM on March 20, 2011 [1 favorite]


I am glad for this post, and the Van Allen Belt post a couple doors down!

Then, there's my poor boyfriend. If he has to hear the words "and here's another neat thing I learned about radiation this week!" just one more time....
posted by evidenceofabsence at 11:24 PM on March 20, 2011 [2 favorites]


The first nuclear reactor was in Africa, 2 billion years ago.

if they're going to go down that path, they mean "the first nuclear reactor on Earth"... because there's another really big one about 8.3 light minutes away, and even if they mean just fission reactors, odds are there have been plenty elsewhere in the universe since planets first started forming...

</pedant>
posted by russm at 11:28 PM on March 20, 2011 [15 favorites]


A remarkable thing about the Oklo reactors is that the highly radioactive waste products stayed put without the elaborate containment we use today on nuclear power plant waste. More than a billion years later, everything is contained within a few meters of its source.

A billion years is the best containment structure there is. After a billion years "highly radioactive waste products" are no longer radioactive. In a billion years there will no longer be any need to contain TMI, Chernobyl, of Fukushima.

Over the span of one thousand million (one billion) years, even radioisotopes with a long ass half-life (like Cesium 137 which has a half life of something like 2 million years) are pretty much depleted.
posted by three blind mice at 11:42 PM on March 20, 2011 [2 favorites]


Fun Fact: The main reason our planet's core hasn't solidified by giving off all its heat into space is ongoing nuclear reactions which replenish that heat.
posted by cman at 11:45 PM on March 20, 2011 [2 favorites]


Previously.
posted by homunculus at 11:50 PM on March 20, 2011


Actually it's probably just the earliest reactor we've discovered. It's more likely that lots of reactors were going shortly after the earth formed.
posted by delmoi at 11:51 PM on March 20, 2011 [1 favorite]


A billion years is the best containment structure there is.

Awesome science fiction story waiting to be written here.
posted by LobsterMitten at 11:56 PM on March 20, 2011 [3 favorites]


A remarkable thing about the Oklo reactors is that the highly radioactive waste products stayed put without the elaborate containment we use today on nuclear power plant waste. More than a billion years later, everything is contained within a few meters of its source.

It's worth noting, but "remarkable" is the wrong word. That is like saying "a remarkable thing about this particular fossilized dinosaur is that 60 million years later, many of its bones are still within a few meters of each other". The staggering geological stability is what allowed the fossil to still exist at all today and thus to be found, it's not some optional extra that the fossil added on for bonus points. It comes with the package.
posted by -harlequin- at 12:07 AM on March 21, 2011 [7 favorites]


Awesome science fiction story waiting to be written here.

Well, exploiting relativity theory only really gets you nuclear waste that lasts longer. Accelerating civilization to rates of near c relative to everything else is not exactly a low-energy solution for dealing with nuclear waste, either. (Though a hilarious idea.) However it does remind me of the "forward-only time travel machine" that the Professor built in Futurama season 6, which really was their best episode in recent memory. Anyway, beanplated.

The staggering geological stability is what allowed the fossil to still exist at all today and thus to be found, it's not some optional extra that the fossil added on for bonus points. It comes with the package.

Yes, classic selection bias.
posted by mek at 12:15 AM on March 21, 2011


ike Cesium 137 which has a half life of something like 2 million years

*cough*
posted by Dr Dracator at 12:33 AM on March 21, 2011 [3 favorites]


Cesium 137 which has a half life of something like 2 million years

I think you meant Neptunium, another byproduct of uranium fission which does have a half life of 2 million years.
posted by dibblda at 12:47 AM on March 21, 2011


People get quite excited that Neptunium has a half-life of two million years. But is that really living? I've heard that the second million tends to drag a bit. You've read all the books in the house, you keep going back to the same restaurants, the kids are 1.99997 million years old and have their own thing going on ...
posted by the quidnunc kid at 1:15 AM on March 21, 2011 [6 favorites]


The late and lamented Damn Interesting covered this. If you've not read the site, I recommend going and reading all of it. Sadly there's a finite amount.
posted by imperium at 1:24 AM on March 21, 2011 [3 favorites]


"cycling multiple times per day"

Led me to this paragraph where I've spent an additional hour in awe:

"Earth does many surprising things, for instance explosions of diamonds, volcanoes of carbonate lava, eruptions of asphalt and red lightning flashing upward toward space. But Earth's neatest trick may be the time it created a nuclear reactor all by itself."

Excellent, relevant and unexpected.
posted by Kale Slayer at 1:46 AM on March 21, 2011 [8 favorites]


It. Began. In Afrika ka ka ka ka ka ka ka ka ka ka.....

Umm... but a earnest question. From the article "Elsewhere in the earth’s crust, on the moon and even in meteorites, uranium 235 atoms make up 0.720 percent of the total." If things like spontaneous nuclear fission can happen, even on boring old (well, young at the time I guess) terra firma, why is it otherwise taken that this isotope ratio is such a universal constant?
posted by adamt at 1:49 AM on March 21, 2011


adamt: The ratio isn't constant, it's been steadily changing over time because U-235 has a much shorter half-life than U-238. 700 million years vs 4.5x10^9 years.

The series of supernovas that provided the source material for the gas cloud that formed our solar system would have originally created more U-235 than U-238 in fact, but that ratio was fixed at the creation of the solar system & the U-235 has been steadily decaying ever since at a faster rate than the U-238, so there's now much less U-235 than U-238.

U-235 and U-238 are very chemically indistinguishable: it's extremely difficult to separate them at all, which is why it takes so much effort to acquire enough U-235 to make an atomic bomb. Hence U-235 and U-238 are completely mixed wherever they are found in the solar system: The total amount of Uranium might vary in different regions, but in any given area of the solar system you'll find U-235 and U-238 in the same ratio as anywhere else.

Does that make sense?
posted by pharm at 2:23 AM on March 21, 2011 [5 favorites]


Sigh. U-235 and U-238 are very chemically indistinguishable
posted by pharm at 2:24 AM on March 21, 2011


IIRC, there is no deep reason behind the constant isotopic composition of uranium; you are right to assume that other values may be found in other parts of the universe. It just happens that all the uranium we have observed so far has the same composition, presumably because --- on a universal scale --- it all comes from the same original blob of matter.
posted by Dr Dracator at 2:25 AM on March 21, 2011


(In reality the ratio of isotopes does vary slightly with location, but the ratio of U-235 to U-238 is constant to roughly 2 significant figures if I read the references correctly, hence the need to explain any significant deviation.)
posted by pharm at 2:34 AM on March 21, 2011


That "explosions of diamonds" link is fascinating. I'm on part 5, you almost made me late for work.
posted by marxchivist at 4:24 AM on March 21, 2011


Are there nuclear reactors at Earth's core? Fission reactors may have been burning for billions of years. 15 May 2008 | Nature
posted by panaceanot at 5:38 AM on March 21, 2011


Nuclear Boy has been pooping a long time.
posted by Mcable at 6:10 AM on March 21, 2011


Fun Fact: The main reason our planet's core hasn't solidified by giving off all its heat into space is ongoing nuclear reactions which replenish that heat.

There aren't any nuclear "reactions" in the earth's core per se. The earth's core is more like Fukushima post-earthquake - no chain reaction, but plenty of decay heat. The Gabon site was a reactor in the true sense - it supported a chain reaction of atoms splitting other atoms.
posted by Popular Ethics at 6:16 AM on March 21, 2011


Hmm.

They say this happened about two billion years ago. And also, about two billion years ago, single-celled organisms first developed respiration.

I freely admit I'm not a scientist and may be talking out of my ass. But could the radiation from these natural reactors have perhaps caused the mutation that lead to developing respiration?
posted by EmpressCallipygos at 6:45 AM on March 21, 2011


Very unlikely EmpressCllipygos. There would have been plenty of ambient radiation around from cosmic rays, general radioactive decay in the rocks and so on. Plus radiation is not the only source of genetic mutations.

(Plus, IIRC that Uranium only dissolves much in water in the presence of Oxygen, so to get deposits like this at all you need Oxygen present in the first place.)
posted by pharm at 6:53 AM on March 21, 2011


"The staggering geological stability is what allowed the fossil to still exist at all today and thus to be found,"

Not only that, but I've noticed that quite often a pair of socks will go into the washer and come out... Together! Other times not so much. And then it's off to the clothing randomizer dryer, where you'd never expect to find the pair of socks together after 40 minutes. And yet, there they are within one clothing item of each other, or in some cases, blatantly, sensuously stuck together, and claiming selection bias right to my face! (To be fair, what's keeping them together is static electricity, but they don't know that.)
posted by sneebler at 7:21 AM on March 21, 2011


Metafilter: I'm not a scientist and may be talking out of my ass.
posted by marxchivist at 7:56 AM on March 21, 2011 [9 favorites]


But could the radiation from these natural reactors have perhaps caused the mutation that lead to developing respiration?

It's doubtful. These reactions and the products produce four types of radiation:
Alpha and beta particles: These are efficiently blocked by a few centimeters of dense material.
Gamma radiation: Most gamma can be blocked by a few feet of rock.
Neutrons: A bit more difficult to block, but neutrons interact fairly well with hydrogen, so groundwater-saturated rock should do the trick.

Unless these deposits were very close to the surface, the additional radiation wouldn't be detectable above background sources.

In addition, respiration is a complex process involving dozens of enzymes. Thankfully, most of them deliver some form of energy or metabolic benefit. A more likely explanation for the complete process is eubacterial gene-swapping and endosymbiosis.
posted by KirkJobSluder at 8:02 AM on March 21, 2011 [2 favorites]


While lowering the top reflector, Slotin's screwdriver slipped a fraction of an inch, allowing the top reflector to fall into place around the core. Instantly there was a flash of blue light and a wave of heat across Slotin's skin; the core had become supercritical, releasing a massive burst of neutron radiation.


Fun fact: the flash of blue light was caused by Cherenkov radiation in the eyes of the observers.

Aaaaggghh
posted by you're a kitty! at 8:16 AM on March 21, 2011 [3 favorites]


I am gob-smacked.
posted by bonobothegreat at 8:33 AM on March 21, 2011


"These reactors are thought to have occurred naturally"

Ok, stop dancing around it and just tell us what you think. Time travel, or ancient aliens? Or nuclear capable dinosaurs?
posted by dirtdirt at 9:38 AM on March 21, 2011 [1 favorite]


i call dibs on the nuclear-capable dinosaurs.
posted by lodurr at 10:21 AM on March 21, 2011


Nuclear-capable dinosaurs are apparently a bad idea.
posted by you're a kitty! at 10:31 AM on March 21, 2011


Pish-posh. What cold possibly go wrong?
posted by lodurr at 10:45 AM on March 21, 2011


Nukasaurus Rex, the Irradiated Carnosaur! I'm for it.
posted by FatherDagon at 10:51 AM on March 21, 2011


A billion years is the best containment structure there is.

Awesome science fiction story waiting to be written here.


StarGate SG-1 beat you to it. Link.
posted by Dark Messiah at 11:15 AM on March 21, 2011


While lowering the top reflector, Slotin's screwdriver slipped a fraction of an inch, allowing the top reflector to fall into place around the core. Instantly there was a flash of blue light and a wave of heat across Slotin's skin; the core had become supercritical, releasing a massive burst of neutron radiation.

This particular incident was fictionalized in the excellent film Fat Man and Little Boy. I think it's on Netflix Instant.
posted by AugieAugustus at 11:54 AM on March 21, 2011


Add "Fossil Reactor 15" to the list of cool names for bands that I will never form.
posted by KingEdRa at 1:05 PM on March 21, 2011


> Sigh

The chemical properties of two isotopes are in general very similar... (my emphasis)
U-235 and U-238 are not chemically identical - the difference in nuclear mass will result in slightly different reaction rates and bond strengths; we see these chemical differences in the isotopes of lighter elements all the time (differential accumulation of carbon and nitrogen isotopes in plants, difficulty growing bacteria on NMR mix in the lab, et cetera).

(Or was it just a grammar flame? If so, a more constructive post might have suggested "nearly" as a substitute for "very".)
posted by overyield at 1:43 PM on March 21, 2011


Oh, well, see? Nukes are perfectly natural. Did you hear that, Ewell? Pass the cigar!
posted by Twang at 2:26 PM on March 21, 2011


overyield: It wasn't a flame as such as I was responding to my own post! But yes, I was exasperated at not spotting the grammatical error & then in turn managed to introduce a new error into the original by turning it into an absolute statement. Double sigh :)
posted by pharm at 3:11 PM on March 21, 2011


There's a "fossil fuel" joke in here somewhere....
posted by schmod at 6:59 PM on March 21, 2011


the quidnunc kid: "People get quite excited that Neptunium has a half-life of two million years. But is that really living? I've heard that the second million tends to drag a bit. You've read all the books in the house, you keep going back to the same restaurants, the kids are 1.99997 million years old and have their own thing going on ..."

Well, you could try and insult everyone in the universe....
posted by Chrysostom at 12:12 PM on March 23, 2011


"Fun fact: the flash of blue light was caused by Cherenkov radiation in the eyes of the observers."

Not quite.
posted by Soupisgoodfood at 2:18 PM on March 26, 2011


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