The Oklo region has now-exhausted Uranium deposits.
From Wikipedia:
"Some of the mined uranium was found to have a lower concentration of uranium-235 than expected, as if it had already been in a nuclear reactor. When geologists investigated they also found products typical of a reactor. They concluded that the deposit had been in a reactor: a natural nuclear fission reactor, around 1.8 to 1.7 billion years BP – in the Paleoproterozoic Era during Precambrian times, during the Statherian period – and continued for a few hundred thousand years, probably averaging less than 100 kW of thermal power during that time. At that time the natural uranium had a concentration of about 3% 235U and could have reached criticality with natural water as neutron moderator allowed by the special geometry of the deposit."
jvanderbot · 37m ago
100 kW for a few hundred thousand years is basically the best sales pitch for nuclear power I've ever heard. Even of "just" heat output.
wjnc · 6h ago
This article could be so much better: How large are the estimated stores of ore that underwent natural fission? How much energy did it release and over how much time? When? Would this be noticable (and to whom)? So many questions, so little information.
I only know (or knew) high school physics, and when entering this in Claude I get an answer but am unable to verify the answer. Claude says 680 kWh gained per 0.03 grams of U-235 lost due to fission. I am left wondering into what the U-235 fizzed into (sorry, pun) and if I should take that into account.
Edit: There we go with modernity. I went to Claude instead of Wikipedia. Wikipedia at least has the answers. Thanks u/b800h. 100kW of heat on average. I can start filling in the blanks now.
adev_ · 5h ago
The 'natural reactor' in Oklo has been discovered by some french researcher from the CEA in the 70s.
There is an entire scientific publication on the topic if it interests you:
I wonder why Claude’s answers aren’t equal or better than Wikipedia - assuming Wikipedia is one of the training datasets. Is the temperature causing it to be probabilistic & other sources are carrying more weight?
lazide · 3h ago
You can think of a LLM as a type of lossy compression of knowledge.
With that in mind, is it really surprising that you don’t get the ‘right’ answer out? Any more than if you compress an image with JPEG, a given pixel isn’t the ‘right’ color anymore either?
They’re both close (kinda) at least, which is the point. If you wanted the exact right answer, don’t use lossy compression - it’ll be expensive in other ways though.
ksenzee · 2h ago
What a great metaphor. I’m adopting that immediately, thank you.
I can't speak for users of Claude, but as a user of Perplexity, having an LLM do a web search has uncovered sources I'd never have considered. The only time I use Google anymore is when I know exactly what I'm looking for.
When I'm in research/discovery mode, I use Perplexity. Its search/analysis is a lot slower than a Google search, but saves me time overall and generally gives me solutions that I'd have to spend time sorting through a Google search to find, in less time than it takes to do so.
wjnc · 3h ago
Claude gave a great answer at the link, at least for me. There might be a plus in learning as well since the answer is well structured with a recognizable style. Say, the scientific article above, has a distinct style and really was not high school physics level.
pfdietz · 5h ago
Uranium was very enriched back at the formation of the Earth, so for a given geometry it would have been much more reactive.
However, uranium ores are often formed due to redox processes, since U(VI) is much more soluble than U(IV). So maybe concentrations wouldn't have been as common back before the Great Oxygenation Event about 2.4 Gya. Still, that leaves ~600 Mya between that point and this reactor, which would be not quite one half life of U235.
legitster · 4h ago
Richard Rhodes brought this up in an interview. He made it a point for critics who say nuclear waste can't be safely disposed of through burial. Well, we have pretty good natural evidence that nuclear fission products can remain buried and undisturbed for a pretty long time!
joe_the_user · 2h ago
I don't disagree that nuclear waste can be disposed of safely under good conditions[1].
But I think a fallacy to claim that natural phenomena should inherently be considered "environmentally safe" in human terms. There are coal seam fires that have been going on for centuries and the pollution of these is just as bad as the pollution generated by human created coal mine fires (and that's truly awful, a significant source of carbon pollution).
[1] The problem with nuclear reactors isn't that their pollution couldn't disposed of with ideal methods but that when they run by for-profit corporations, you will always have the company skirting the edge of what's safe 'cause corporations just go bankrupt with catastrophic events and so their risk-reward behavior isn't the risk-reward optima for humanity.
glompers · 2h ago
> There are coal seam fires that have been going on for centuries and the pollution of these is just as bad as the pollution generated by human created coal mine fires (and that's truly awful, a significant source of carbon pollution).
Has CO2 fire suppression been unsuccessfully attempted in these seams? Since nobody is underground and we know how to inject CO2 into underground deposits at various pressures, it seems like it would be a good candidate. Plus, with rotary steerable drilling, we could come in laterally (from a safe location above ground) to as many depths of injection as necessary.
a11r · 1h ago
These are large coal seams with significant exposure to the atmosphere. See https://en.wikipedia.org/wiki/Jharia_coalfield for an example. That excavator in the picture is not trying to put out the fire, it is just mining coal that happens to be burning. Spray some water, put out the fire and ship it off to customers.
legitster · 2h ago
No one is saying that it's "inherently" safe but there are a lot of people who claim it is inherently unsafe which is clearly untrue.
Manuel_D · 2h ago
What are the conditions under which nuclear waste buried a mile deep in bedrock will post a risk to society?
bobmcnamara · 2h ago
1) the assumption that because something can be done safely it will be done safely
3) exploding waste barrels due to corner cutting in kitty litter selection exposing surface workers and contaminating the work area - only 1/2 mile down but this type of accident is depth independent https://www.latimes.com/nation/la-na-new-mexico-nuclear-dump...
4) fires
5) lack of a safety culture
6) communicating to future peoples not to mine here
7) long term structural stability and management (ex: Morsleben radioactive waste repository and Schacht Asse II)
Manuel_D · 56m ago
2) I asked about waste buried in the ground, not in transit.
3) if a waste barrel explodes, somehow, underground how does the waste make it's way through a mile of bedrock?
4) Again, how does a fire bring the wast up through a mile of bedrock?
5) This is just a vague statement.
6) So the concern is that future society will forget that this is a waste site, mine a mile deep and retrieve waste, and never figure out that the waste is bad for them? This is rather specific hypothetical that IMO demonstrates just how hard it is for a nuclear waste site to result in contamination.
lostlogin · 9m ago
Regarding 3) and 4): Ground water contamination.
Manuel_D · 1m ago
You can dig in bedrock that has no groundwater.
Furthermore, naturally occurring uranium exists in groundwater and needs to be filtered out in places where levels exceed safe limits. So it's not like burying waste is creating a new problem: https://www.kqed.org/stateofhealth/120396/uranium-contaminat...
AtlasBarfed · 46m ago
I look forward to your revolutionary nuclear waste teleportation device.
Just to call it explicitly, because I think this is one of the big points of misunderstanding between pro- and anti-nuclear people (take that as a very rough categorization and not an accusation) -
There is a difference between “something can be done correctly” and “something is likely to be done correctly.” Nuclear advocates I’ve read tend to argue the former - it’s possible to have safe reactors, it’s possible to keep the waste sequestered safely, there’s not a technical reason why nuclear is inherently unsafe. Skeptics tend to be making a different argument - not that it’s not possible to do things safely and correctly, but that in our current late-capitalist milieu, it’s almost impossible that we _will_. It’s not an argument about capability, it’s an argument about will and what happens in bureaucracies, both public and private.
Terr_ · 23m ago
Yeah, if it were as easy as proponents claim, things like Hanford would already be an inactive site with a memorial park on top.
Whether it's technology, economics, or politics, clearly the state of the art is deficient because we currently have deficiencies.
AtlasBarfed · 47m ago
It's kind of the nature of a heavily regulated safety industry. The industry comes to resent the safety regulations. And therefore they will fail.
It's not even a a matter of mundane human error when executing procedures over and over again.
It's that the entire managerial pyramid gradually and slowly erodes
sllabres · 43m ago
It's not a mile deep, but I think the depth isn't the problem here:
The Asse II site used an existing mine to avoid having to excavate a new tunnel, which subsequently flooded.
Loughla · 2h ago
Burying it in a cheaper place that happens to flood occasionally?
legitster · 2h ago
Insisting on only worst case scenarios is such a bad faith argument. OP specifically asked about deep repositories.
It would be like having a discussion about green energy and insisting that people should assume dams will fail or that blades are going to fly off of turbines.
krunck · 3h ago
This is nonsense. Yep, after 2 billion years this thing is now safe to touch. But that had nothing to do with it's burial.
We at least have pretty good evidence that nuclear fission products can be exposed to groundwater/hydrothermal fluids for a pretty long time.
foobarian · 3h ago
> All natural uranium today contains 0.720% of U-235. If you were to extract it from the Earth’s crust, or from rocks from the moon or in meteorites, that’s what you would find. But that bit of rock from Oklo contained only 0.717%.
Heh. The garbage web software developer me would have just called it good enough
Would be really interesting to know what the error bars on those figures look like
teuobk · 2h ago
Per NIST[1], the value is 0.7204% +/- 0.0006%, with the uncertainty representing one standard deviation.
You have me wondering about that as well. If the uranium was going to be enriched for use in a light-water reactor (I would guess it was), maybe the difference translates into needing more stages of enrichment to reach the required level?
Analemma_ · 3h ago
I think it would've been good enough for the miners too, if not for the fact that nuclear arms control treaties require every gram of U-235 to be accounted for. When they were digging it out of the ground and found it was less enriched than it should've been, this needed to be explained. It has always fascinated me to think that this natural phenomenon could and probably would have remained unknown forever if not for these treaties and agreements.
Aardwolf · 5h ago
> All natural uranium today contains 0.720% of U-235.
That's related to the material of our solar system all coming from the same supernova explosion or similar, right? Does this apply to our entire milky way or just the solar system? What if parts collided with material of _other_ origins and some of that is on Earth, then there could be different mixes, right?
philipkglass · 4h ago
It's related to how long ago the uranium was formed:
We can calculate the abundances of U-235 and U-238 at the time the Earth was formed. Knowing further that the production ratio of U-235 to U-238 in a supernova is about 1.65, we can calculate that if all of the uranium now in the solar system were made in a single supernova, this event must have occurred some 6.5 billion years ago.
This 'single stage' is, however, an oversimplification...
The really interesting thing is that phrase "the production ratio of U-235 to U-238 in a supernova is about 1.65"; the now-rare U-235 is actually more abundant than U-238 in the fresh debris of a supernova. Prolonged aging has preserved more U-238 (half life 4.47 billion years) than U-235 (half life 0.704 billion years) to the point that U-238 is now much more terrestrially abundant. If Earth had been formed with uranium that rich in U-235, there would have been Oklo events all over the place. Uranium wouldn't need isotopic enrichment to be used as fuel in light water reactors. Nuclear fission would probably have been discovered early in the 19th century, soon after the element itself was recognized, because any substantial quantity dissolved in aqueous solution would have reached criticality.
cryptonector · 3h ago
I read GP's question really as: "did all Uranium on Earth come from the same source?" and your answer implies "yes". I think that's right.
The fact that everywhere we see the same U-235/U-238 ratio or very close (Oklo) strongly implies either a single source (supernova) or that if it was more than one source they were all at roughly the same time (6.5 billion years ago), with the latter seeming [to me] less likely, so a single source at 6.5 billion years ago is what makes sense. Unless there were many supernovae and their remnants mixed quite well in our corner of the galaxy where our sun was born.
lazide · 4h ago
It’s interesting to extrapolate that to the early earth - radioactive decay and fission interactions likely play a much larger role than we are able to reliably model. Okla is somewhat unique in that the formation survived for us to dig it up - most from that time would not.
mandevil · 4h ago
This is just in our little corner of the Milky Way, but not thought to be the result of just one supernova. I last looked into this about a decade ago so I might be behind the times, but at that time the most popular theory was that the cloud that became our Solar System was the result of thousands of supernova scattering and mixing atoms, across both the first two generations of stars (the Sun is considered to be a third-generation star), and that mixing is thought to be an important factor in making it complex enough to have rocky inner planets, gaseous outer planets, etc.
BurningFrog · 5h ago
Grok says: At Earth's formation ~4.5 billion years ago, natural uranium contained approximately 23.2% U-235
These numbers are probably only for the local corner of the galaxy. It depends on when the supernova(s) that created the uranium exploded.
_Algernon_ · 5h ago
We all have access to Grok and other AI models, and we will ask it if we want it's bullshit hallucinations. There is no point polluting HN with this trash.
BurningFrog · 3h ago
Anyone can look it up, yet I was the only one who did.
CamperBob2 · 3h ago
Is it wrong?
kkwteh · 5h ago
Maybe it’s a remnant from a nuclear ancient civilization.
geocrasher · 4h ago
Maybe it's a sign of a future time travelling civilization with nuclear power but poor navigation, warped straight into the mantle Earth's crust :D
Gregaros · 2h ago
I thought where you were going with his was "that realized the best way to dispose of their nuclear waste was to dump it in the deep past." I’d read that novel.
geocrasher · 1h ago
Only to mine it later and re-use it over and over again. The 5 billion year long recycling program.
julienchastang · 4h ago
A civilization (even perhaps extraterrestrial) that possessed nuclear energy? Unlikely, but still fun to think about! ;-)
From Wikipedia:
"Some of the mined uranium was found to have a lower concentration of uranium-235 than expected, as if it had already been in a nuclear reactor. When geologists investigated they also found products typical of a reactor. They concluded that the deposit had been in a reactor: a natural nuclear fission reactor, around 1.8 to 1.7 billion years BP – in the Paleoproterozoic Era during Precambrian times, during the Statherian period – and continued for a few hundred thousand years, probably averaging less than 100 kW of thermal power during that time. At that time the natural uranium had a concentration of about 3% 235U and could have reached criticality with natural water as neutron moderator allowed by the special geometry of the deposit."
I only know (or knew) high school physics, and when entering this in Claude I get an answer but am unable to verify the answer. Claude says 680 kWh gained per 0.03 grams of U-235 lost due to fission. I am left wondering into what the U-235 fizzed into (sorry, pun) and if I should take that into account.
Edit: There we go with modernity. I went to Claude instead of Wikipedia. Wikipedia at least has the answers. Thanks u/b800h. 100kW of heat on average. I can start filling in the blanks now.
There is an entire scientific publication on the topic if it interests you:
https://www.sciencedirect.com/science/article/abs/pii/S00167...
With that in mind, is it really surprising that you don’t get the ‘right’ answer out? Any more than if you compress an image with JPEG, a given pixel isn’t the ‘right’ color anymore either?
They’re both close (kinda) at least, which is the point. If you wanted the exact right answer, don’t use lossy compression - it’ll be expensive in other ways though.
When I'm in research/discovery mode, I use Perplexity. Its search/analysis is a lot slower than a Google search, but saves me time overall and generally gives me solutions that I'd have to spend time sorting through a Google search to find, in less time than it takes to do so.
However, uranium ores are often formed due to redox processes, since U(VI) is much more soluble than U(IV). So maybe concentrations wouldn't have been as common back before the Great Oxygenation Event about 2.4 Gya. Still, that leaves ~600 Mya between that point and this reactor, which would be not quite one half life of U235.
But I think a fallacy to claim that natural phenomena should inherently be considered "environmentally safe" in human terms. There are coal seam fires that have been going on for centuries and the pollution of these is just as bad as the pollution generated by human created coal mine fires (and that's truly awful, a significant source of carbon pollution).
[1] The problem with nuclear reactors isn't that their pollution couldn't disposed of with ideal methods but that when they run by for-profit corporations, you will always have the company skirting the edge of what's safe 'cause corporations just go bankrupt with catastrophic events and so their risk-reward behavior isn't the risk-reward optima for humanity.
Has CO2 fire suppression been unsuccessfully attempted in these seams? Since nobody is underground and we know how to inject CO2 into underground deposits at various pressures, it seems like it would be a good candidate. Plus, with rotary steerable drilling, we could come in laterally (from a safe location above ground) to as many depths of injection as necessary.
2) transportation to the site: https://static.ewg.org/files/nuclearwaste/plumes/national.pd...
3) exploding waste barrels due to corner cutting in kitty litter selection exposing surface workers and contaminating the work area - only 1/2 mile down but this type of accident is depth independent https://www.latimes.com/nation/la-na-new-mexico-nuclear-dump...
4) fires
5) lack of a safety culture
6) communicating to future peoples not to mine here
7) long term structural stability and management (ex: Morsleben radioactive waste repository and Schacht Asse II)
3) if a waste barrel explodes, somehow, underground how does the waste make it's way through a mile of bedrock?
4) Again, how does a fire bring the wast up through a mile of bedrock?
5) This is just a vague statement.
6) So the concern is that future society will forget that this is a waste site, mine a mile deep and retrieve waste, and never figure out that the waste is bad for them? This is rather specific hypothetical that IMO demonstrates just how hard it is for a nuclear waste site to result in contamination.
Furthermore, naturally occurring uranium exists in groundwater and needs to be filtered out in places where levels exceed safe limits. So it's not like burying waste is creating a new problem: https://www.kqed.org/stateofhealth/120396/uranium-contaminat...
There is a difference between “something can be done correctly” and “something is likely to be done correctly.” Nuclear advocates I’ve read tend to argue the former - it’s possible to have safe reactors, it’s possible to keep the waste sequestered safely, there’s not a technical reason why nuclear is inherently unsafe. Skeptics tend to be making a different argument - not that it’s not possible to do things safely and correctly, but that in our current late-capitalist milieu, it’s almost impossible that we _will_. It’s not an argument about capability, it’s an argument about will and what happens in bureaucracies, both public and private.
Whether it's technology, economics, or politics, clearly the state of the art is deficient because we currently have deficiencies.
It's not even a a matter of mundane human error when executing procedures over and over again.
It's that the entire managerial pyramid gradually and slowly erodes
https://en.wikipedia.org/wiki/Asse_II_mine
The Asse II site used an existing mine to avoid having to excavate a new tunnel, which subsequently flooded.
It would be like having a discussion about green energy and insisting that people should assume dams will fail or that blades are going to fly off of turbines.
We at least have pretty good evidence that nuclear fission products can be exposed to groundwater/hydrothermal fluids for a pretty long time.
Heh. The garbage web software developer me would have just called it good enough
Would be really interesting to know what the error bars on those figures look like
[1] https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl...
That's related to the material of our solar system all coming from the same supernova explosion or similar, right? Does this apply to our entire milky way or just the solar system? What if parts collided with material of _other_ origins and some of that is on Earth, then there could be different mixes, right?
https://world-nuclear.org/information-library/nuclear-fuel-c...
We can calculate the abundances of U-235 and U-238 at the time the Earth was formed. Knowing further that the production ratio of U-235 to U-238 in a supernova is about 1.65, we can calculate that if all of the uranium now in the solar system were made in a single supernova, this event must have occurred some 6.5 billion years ago.
This 'single stage' is, however, an oversimplification...
The really interesting thing is that phrase "the production ratio of U-235 to U-238 in a supernova is about 1.65"; the now-rare U-235 is actually more abundant than U-238 in the fresh debris of a supernova. Prolonged aging has preserved more U-238 (half life 4.47 billion years) than U-235 (half life 0.704 billion years) to the point that U-238 is now much more terrestrially abundant. If Earth had been formed with uranium that rich in U-235, there would have been Oklo events all over the place. Uranium wouldn't need isotopic enrichment to be used as fuel in light water reactors. Nuclear fission would probably have been discovered early in the 19th century, soon after the element itself was recognized, because any substantial quantity dissolved in aqueous solution would have reached criticality.
The fact that everywhere we see the same U-235/U-238 ratio or very close (Oklo) strongly implies either a single source (supernova) or that if it was more than one source they were all at roughly the same time (6.5 billion years ago), with the latter seeming [to me] less likely, so a single source at 6.5 billion years ago is what makes sense. Unless there were many supernovae and their remnants mixed quite well in our corner of the galaxy where our sun was born.
These numbers are probably only for the local corner of the galaxy. It depends on when the supernova(s) that created the uranium exploded.
https://news.ycombinator.com/item?id=17736262
um, stars?
https://en.wikipedia.org/wiki/Natural_nuclear_fission_reacto...