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."
Cheap until it isn't. I wonder what has been the actual cost per kWh of nuclear power in Japan once factored in the price of Fukushima's disaster (between 200 and 600 billion dollars).
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!
From another perspective, its safety lasted almost exactly as long as it took for humans to come around. That window is now closed for future deposits.
(I'm pro-nuclear but that's a hilariously bad argument.)
Except for Finland nobody has actually created a long term geologic disposal site. Like so many problems, the issue is dominated by political coordination, not physical limits.
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.
> 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.
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.
Apparently in mines they are sometimes extinguished with nitrogen. For less contained ones, injecting water or mud, while trying to seal off the ground with impermeable clay to halt oxygen and hopefully choke the fumes. Their scope can be huge though, and they generate a lot of energy which can cause subsidence to open up new passages. The Centralia fire in the US is apparently 15km².
I have a question on rotary steerable drilling. I gather we're only talking about a degree or less of deflection on the steering head. But how does the km's long rest of the stack behind the head snake through the curves? Is it like rail cars, with a little bit of angular bend allowed at the connection of each segment?
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)
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.
2/3/4) Please see historical data above regarding three burial sites. Practically today, these sites are built by mining.
5) Industry term. Operationalizing any significant system will involve human beings, and with it their workplace culture. You can read about it here: https://mshasafetyservices.com/fostering-a-culture-of-safety.... Many mining hese were written in blood.
6) No, the concern is that people may be harmed. You see we've lost track of radioactive waste in the past. And humans are remarkably curious. Often we've figured it out before anyone was harmed. Sometimes sadly not. But the harm is the concern, not the lack of knowledge of harm.
The example you linked above is disposal of nuclear weapons waste, not nuclear power generation. This isn't even the same material (plutonium vs uranium). Sure, there were plenty of bad nuclear waste disposal programs in the early cold war, but this has quite limited relevance to nuclear power generation.
And again, the question remains how people may be harmed by nuclear waste buried in bedrock half a kilometer underground? A even if a buried waste canister spontaneously combusts, how does the waste make it through half a kilometer of rock? In order for an unknown harm to occur, harm first has to actually occur.
This kind of appeal to an unknown harm can be used to arbitrarily object to anything.
"We need to stop building solar panels and wind turbines because they have the potential to cause an unknown harm. You disagree that these systems have the potential to cause harm? Well of course you can't know this, because it's an unknown harm that we're trying to prevent. How can you possibly disprove the existence of an unknown harm?"
>> Nuclear power is an incredible technology, but understand that the nuclear industry has done little to earn trust. Just feels like an abusive ex plastered on the porch shouting "it'll be different this time I've changed" and doesn't inspire confidence.
> Care to elaborate on what you mean by this? Because even if you include Chernobyl, nuclear power is one of the safest form of energy generation: https://ourworldindata.org/safest-sources-of-energy. It's 100x safer than dams. Include only western plants and it's the safest form of energy generation.
I should also add that on average nuclear power releases less radioactivity than coal.
I grew up in a place and time where nuclear waste was routinely dumped, records lost, EPA government consultants lied, and people got sick. Nobody was held accountable other than token fines.
> I grew up in a place and time where nuclear waste was routinely dumped, records lost, EPA government consultants lied, and people got sick. Nobody was held accountable other than token fines.
Can you provide even one example where nuclear waste from power generation - not nuclear weapons production - got people sick in the United States?
> This isn't even the same material (plutonium vs uranium).
Please note that these are both chemically and radioactively harmful to people.
> Sure, there were plenty of bad nuclear waste disposal programs in the early cold war, but this has quite limited relevance to nuclear power generation.
That's what they said in the 00s, 90s, 80s, 70s...
> In order for an unknown harm to occur, harm first has to actually occur.
Nuclear power is an incredible technology, but understand that the nuclear industry has done little to earn trust. Just feels like an abusive ex plastered on the porch shouting "it'll be difficult this time I've changed" and doesn't inspire confidence.
> Please note that these are both chemically and radioactively harmful to people.
Again, the point is that your link is about disposal of plutonium from nuclear weapons productions. Not spent uranium fuel from power generation.
> Nuclear power is an incredible technology, but understand that the nuclear industry has done little to earn trust. Just feels like an abusive ex plastered on the porch shouting "it'll be difficult this time I've changed" and doesn't inspire confidence.
Care to elaborate on what you mean by this? Because even if you include Chernobyl, nuclear power is one of the safest form of energy generation: https://ourworldindata.org/safest-sources-of-energy. It's 100x safer than dams. Include only western plants and it's the safest form of energy generation.
It's not like an abusive ex promising to have changed. It's a lot more like a very respectful partner that your hippie friends hate for incoherent reasons.
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...
Sure, but the important point is that we already have infrastructure deployed to detect and remove uranium from the water supply on account of naturally occurring uranium.
It is. Presumably your fear is that uranium from spent fuel might somehow contaminate water supplies, and cause illness. But we already monitor water for contamination from naturally occurring uranium, and have the infrastructure to remove it.
So what happens if uranium from nuclear waste somehow works its way into the water supply? We'll detect it and remove it in water treatment, just like how we remove contamination from naturally occurring uranium.
The primary transportation risk is that spent fuel contains cesium metal, which is reactive with air and water, so if you expose it to air you get a fire.
It seems like a pretty obvious solution to this would be to purposely do the reaction under controlled conditions before transporting it, so then you're transporting stable cesium compounds instead of elemental cesium metal.
Yes, but when we want to store something in the range of million years, it is a bit early to say that 30 years are sufficient as a ultimate proof that nothing leaks.
Now I believe it can be done safely, but only if monitored all the time with good care. But that is expensive and humans tend to skimp.
You don't need nuclear waste to be stored for millions of years, after a hundred or so anything of exceptional danger has decayed and what is left will be such a low level of radiation that common clay bricks are just as much of a risk. The "hotter" a nuclear material is, the faster it decays, and materials that remain radioactive for thousands of years are not especially radioactive.
Again, when you bury uranium half a kilometer deep in an area with no aquifer, how will it ever result in contamination?
The only real scenarios are deliberate excavation, and a meteor impact directly on the waste repository. Neither of which are particularly likely scenarios.
Because the ground is not static. And we are just starting to understand what is going on down there. So yes, there are sites that remained quite unchanged (like with the natural fission reactor), but personally I remain sceptical with such statements.
Are we supposed to hold off on developing the only geographically independent and non-intermittent form of clean energy because of some vague nebulous fear that waste buried half a kilometer deep in bedrock will come back up to the surface and harm people... somehow?
No, but maybe we should not pretend all is super safe and always will be, when we cannot know currently.
Or rather we do know that the initial promises of reactor safety were also quite overconfident. So people assume the same of permanent storage of the waste.
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.
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.
Not sure I'd call it safe to touch. Getting with 5cm for an hour gives you as much radiation as a 8 hour flight. I wouldn't want touch it, make jewelry from it, or any substantial near promity. Not to mention if it was "only" a billion years ago it would be MUCH MUCH worse.
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.
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?
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.
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.
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.
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.
> 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
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?
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.
> 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?
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.
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.
If the Uranium came from multiple supernovae, then why is it shocking that earth has different concentrations of U235? Moreover, how is it proof of a past fission reaction?
What if that "part" of U235 came from a separate supernova which is a little older and some more of its U235 had already decayed?
There were unusual elements characteristic of the decay chain following a fission.
After a U-235 atom undergoes fission, one of the outcomes is it releases Barium and Krypton (and some neutrons), which then eventually decay to stable/semi-stable elements. If one of those stable elements is common in the deposit but otherwise rare naturally, it would point to a nuclear reaction having occurred.
Also note that the U-235 decay chain generally looks different from the decay chain following a fission reaction of U-235.
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.
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.
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.
In order to know whether or not the AI was wrong, you'd need to do some research. Otherwise it's about as reliable as any "fact" some random person on the internet claims to be true.
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.
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."
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.
Its impressive the amount of clean, cheap energy that's been locked away because of fearmongering tales from well before many were even alive.
Cheap until it isn't. I wonder what has been the actual cost per kWh of nuclear power in Japan once factored in the price of Fukushima's disaster (between 200 and 600 billion dollars).
It is natural and reasonable to be of two minds on the matter. Surely that’s not controversial.
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!
From another perspective, its safety lasted almost exactly as long as it took for humans to come around. That window is now closed for future deposits.
(I'm pro-nuclear but that's a hilariously bad argument.)
Except for Finland nobody has actually created a long term geologic disposal site. Like so many problems, the issue is dominated by political coordination, not physical limits.
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.
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.
> 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.
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.
Apparently in mines they are sometimes extinguished with nitrogen. For less contained ones, injecting water or mud, while trying to seal off the ground with impermeable clay to halt oxygen and hopefully choke the fumes. Their scope can be huge though, and they generate a lot of energy which can cause subsidence to open up new passages. The Centralia fire in the US is apparently 15km².
I have a question on rotary steerable drilling. I gather we're only talking about a degree or less of deflection on the steering head. But how does the km's long rest of the stack behind the head snake through the curves? Is it like rail cars, with a little bit of angular bend allowed at the connection of each segment?
What are the conditions under which nuclear waste buried a mile deep in bedrock will post a risk to society?
1) the assumption that because something can be done safely it will be done safely
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)
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.
2/3/4) Please see historical data above regarding three burial sites. Practically today, these sites are built by mining.
5) Industry term. Operationalizing any significant system will involve human beings, and with it their workplace culture. You can read about it here: https://mshasafetyservices.com/fostering-a-culture-of-safety.... Many mining hese were written in blood.
6) No, the concern is that people may be harmed. You see we've lost track of radioactive waste in the past. And humans are remarkably curious. Often we've figured it out before anyone was harmed. Sometimes sadly not. But the harm is the concern, not the lack of knowledge of harm.
The example you linked above is disposal of nuclear weapons waste, not nuclear power generation. This isn't even the same material (plutonium vs uranium). Sure, there were plenty of bad nuclear waste disposal programs in the early cold war, but this has quite limited relevance to nuclear power generation.
And again, the question remains how people may be harmed by nuclear waste buried in bedrock half a kilometer underground? A even if a buried waste canister spontaneously combusts, how does the waste make it through half a kilometer of rock? In order for an unknown harm to occur, harm first has to actually occur.
This kind of appeal to an unknown harm can be used to arbitrarily object to anything.
"We need to stop building solar panels and wind turbines because they have the potential to cause an unknown harm. You disagree that these systems have the potential to cause harm? Well of course you can't know this, because it's an unknown harm that we're trying to prevent. How can you possibly disprove the existence of an unknown harm?"
>> Nuclear power is an incredible technology, but understand that the nuclear industry has done little to earn trust. Just feels like an abusive ex plastered on the porch shouting "it'll be different this time I've changed" and doesn't inspire confidence.
> Care to elaborate on what you mean by this? Because even if you include Chernobyl, nuclear power is one of the safest form of energy generation: https://ourworldindata.org/safest-sources-of-energy. It's 100x safer than dams. Include only western plants and it's the safest form of energy generation.
I should also add that on average nuclear power releases less radioactivity than coal.
I grew up in a place and time where nuclear waste was routinely dumped, records lost, EPA government consultants lied, and people got sick. Nobody was held accountable other than token fines.
> I grew up in a place and time where nuclear waste was routinely dumped, records lost, EPA government consultants lied, and people got sick. Nobody was held accountable other than token fines.
Can you provide even one example where nuclear waste from power generation - not nuclear weapons production - got people sick in the United States?
> This isn't even the same material (plutonium vs uranium).
Please note that these are both chemically and radioactively harmful to people.
> Sure, there were plenty of bad nuclear waste disposal programs in the early cold war, but this has quite limited relevance to nuclear power generation.
That's what they said in the 00s, 90s, 80s, 70s...
> In order for an unknown harm to occur, harm first has to actually occur.
Nuclear power is an incredible technology, but understand that the nuclear industry has done little to earn trust. Just feels like an abusive ex plastered on the porch shouting "it'll be difficult this time I've changed" and doesn't inspire confidence.
> Please note that these are both chemically and radioactively harmful to people.
Again, the point is that your link is about disposal of plutonium from nuclear weapons productions. Not spent uranium fuel from power generation.
> Nuclear power is an incredible technology, but understand that the nuclear industry has done little to earn trust. Just feels like an abusive ex plastered on the porch shouting "it'll be difficult this time I've changed" and doesn't inspire confidence.
Care to elaborate on what you mean by this? Because even if you include Chernobyl, nuclear power is one of the safest form of energy generation: https://ourworldindata.org/safest-sources-of-energy. It's 100x safer than dams. Include only western plants and it's the safest form of energy generation.
It's not like an abusive ex promising to have changed. It's a lot more like a very respectful partner that your hippie friends hate for incoherent reasons.
Regarding 3) and 4): Ground water contamination.
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...
Heavy metal and radiological exposure is not a boolean safe/unsafe.
Sure, but the important point is that we already have infrastructure deployed to detect and remove uranium from the water supply on account of naturally occurring uranium.
That's...not a very good point.
It is. Presumably your fear is that uranium from spent fuel might somehow contaminate water supplies, and cause illness. But we already monitor water for contamination from naturally occurring uranium, and have the infrastructure to remove it.
So what happens if uranium from nuclear waste somehow works its way into the water supply? We'll detect it and remove it in water treatment, just like how we remove contamination from naturally occurring uranium.
I look forward to your revolutionary nuclear waste teleportation device.
The primary transportation risk is that spent fuel contains cesium metal, which is reactive with air and water, so if you expose it to air you get a fire.
It seems like a pretty obvious solution to this would be to purposely do the reaction under controlled conditions before transporting it, so then you're transporting stable cesium compounds instead of elemental cesium metal.
The cesium in spent fuel is not in the form of cesium metal. The cesium there is already oxidized to the +1 oxidation state, as it is in cesium salts.
Teleportation? You dig a tunnel underground, put the waste there, and fill the tunnel. It's been done before, it's not revolutionary engineering: https://en.m.wikipedia.org/wiki/Onkalo_spent_nuclear_fuel_re...
The point was, you cannot ignore the risks of transportation, if you only have some safe spots to burry it.
And what you linked is still under construction. We don't know yet, if it really works safe long term, or if there will be future costs.
Finland has two other disposal sites in operation since the 90s: https://en.m.wikipedia.org/wiki/Deep_geological_repository
Yes, but when we want to store something in the range of million years, it is a bit early to say that 30 years are sufficient as a ultimate proof that nothing leaks.
Now I believe it can be done safely, but only if monitored all the time with good care. But that is expensive and humans tend to skimp.
You don't need nuclear waste to be stored for millions of years, after a hundred or so anything of exceptional danger has decayed and what is left will be such a low level of radiation that common clay bricks are just as much of a risk. The "hotter" a nuclear material is, the faster it decays, and materials that remain radioactive for thousands of years are not especially radioactive.
Again, when you bury uranium half a kilometer deep in an area with no aquifer, how will it ever result in contamination?
The only real scenarios are deliberate excavation, and a meteor impact directly on the waste repository. Neither of which are particularly likely scenarios.
Because the ground is not static. And we are just starting to understand what is going on down there. So yes, there are sites that remained quite unchanged (like with the natural fission reactor), but personally I remain sceptical with such statements.
Half a kilometer isn't particularly deep. There are dozens of mines over 2 KM deep: https://en.wikipedia.org/wiki/List_of_deepest_mines
Are we supposed to hold off on developing the only geographically independent and non-intermittent form of clean energy because of some vague nebulous fear that waste buried half a kilometer deep in bedrock will come back up to the surface and harm people... somehow?
No, but maybe we should not pretend all is super safe and always will be, when we cannot know currently.
Or rather we do know that the initial promises of reactor safety were also quite overconfident. So people assume the same of permanent storage of the waste.
> It's been done before, it's not revolutionary engineering: https://en.m.wikipedia.org/wiki/Onkalo_spent_nuclear_fuel_re...
It's not even open yet.
Finland has been operating two other sites for decades: https://news.ycombinator.com/item?id=44332413
If nuclear waste disposal were what is holding back nuclear energy, it would be in great shape. It's not a primary blocking problem.
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.
Yeah, if waste management was as viable as proponents claim, places like Hanford [0] 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 persistent deficiencies.
[0] https://en.m.wikipedia.org/wiki/Hanford_Site
It's politics. The US already built a waste site in Yucca Mountain, but never bothered to actually use it for political reasons.
Digging a shaft half a kilometer into bedrock and sealing it is not state of the art.
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
It's not a mile deep, but I think the depth isn't the problem here:
https://en.wikipedia.org/wiki/Asse_II_mine
This is the one I was referring to, though I guess it's just over half a kilometer deep: https://en.m.wikipedia.org/wiki/Onkalo_spent_nuclear_fuel_re...
The Asse II site used an existing mine to avoid having to excavate a new tunnel, which subsequently flooded.
Burying it in a cheaper place that happens to flood occasionally?
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.
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Can you link me?
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.
Not sure I'd call it safe to touch. Getting with 5cm for an hour gives you as much radiation as a 8 hour flight. I wouldn't want touch it, make jewelry from it, or any substantial near promity. Not to mention if it was "only" a billion years ago it would be MUCH MUCH worse.
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.
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:
https://www.sciencedirect.com/science/article/abs/pii/S00167...
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?
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.
What a great metaphor. I’m adopting that immediately, thank you.
Wikipedia is the best first point of entry, but if you do use Claude, just tell it to do web search for you: https://claude.ai/share/73e67582-3e03-454b-aa12-e8906bd7b3fd
Why not just do a web search?
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.
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.
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.
> 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
Per NIST[1], the value is 0.7204% +/- 0.0006%, with the uncertainty representing one standard deviation.
[1] https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl...
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?
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.
> 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?
It's related to how long ago the uranium was formed:
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.
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.
I don't understand so bear with me.
If the Uranium came from multiple supernovae, then why is it shocking that earth has different concentrations of U235? Moreover, how is it proof of a past fission reaction?
What if that "part" of U235 came from a separate supernova which is a little older and some more of its U235 had already decayed?
There were unusual elements characteristic of the decay chain following a fission.
After a U-235 atom undergoes fission, one of the outcomes is it releases Barium and Krypton (and some neutrons), which then eventually decay to stable/semi-stable elements. If one of those stable elements is common in the deposit but otherwise rare naturally, it would point to a nuclear reaction having occurred.
Also note that the U-235 decay chain generally looks different from the decay chain following a fission reaction of U-235.
This is excellent. I love your depth of knowledge in this subject. I learned a lot from this clear comment.
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.
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.
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.
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.
Is it wrong?
That's a good question.
In order to know whether or not the AI was wrong, you'd need to do some research. Otherwise it's about as reliable as any "fact" some random person on the internet claims to be true.
Talk about missing the point. Why should I spend my time fact checking the output of a glorified, stochastic parrot?
Anyone can look it up, yet I was the only one who did.
You didn't look anything up. You prompted a stochastic parrot.
Fun aside - Oklo is also the name of a successful YC company that makes a passively-safe nuclear reactor - https://www.oklo.com
Then they picked a very clever name.
Maybe it’s a remnant from a nuclear ancient civilization.
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
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.
Only to mine it later and re-use it over and over again. The 5 billion year long recycling program.
A civilization (even perhaps extraterrestrial) that possessed nuclear energy? Unlikely, but still fun to think about! ;-)
(2018)
https://news.ycombinator.com/item?id=17736262
Or a remnant of a nuclear war in a riotous time
https://en.wikipedia.org/wiki/Silurian_hypothesis
> only known natural nuclear reactor
um, stars?
the word "fission" is missing
https://en.wikipedia.org/wiki/Natural_nuclear_fission_reacto...
um, “Earth’s”?
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