"Stable" here means mechanically stable (they don't fall apart as quickly as was expected), not radiologically stable (the radioactive elements, of course, still decay at their normal rate).
For radionuclides more long-livd means less radioactive per unit of time, though. Of course uranium compounds can be toxic in the chemical sense as well, but I’m unsure if uranium compounds make it to the top threats in that list compared to e.g. arsenic and lead.
Of course radioactivity needs to be respected, and the exclusion zone is there for a reason due to factors such as hot spots.
This is "long-lived" in the ecological sense, not radiological. The grains of uranium oxide dust remain grains of uranium oxide dust, rather than breaking apart. If you ingest a few molecules of uranium oxide, it pretty much doesn't matter, you're fine¹. Ingest these dust particles, not so much. It's a question of concentration, and it seems that it's not diluting out naturally.
(P.S.: the radiological stability and lifetime of uranium doesn't make much sense to question; the dust flakes aren't large & concentrated enough to significantly shorten their half-life due to their own neutron emissions cascading and this isn't what the study was researching. Note the article talks about weathering: "It remains largely unclear why these particles weather at different rates in their environment.")
It’s hard to call them “rods” at this point, since they melted and then cooled into tiny metallic droplets and shards after they were ejected in the explosion.
It means "mechanically stable", which could be either good or bad depending on the question, but is generally a limited good thing.
At the least, it means these particular compounds aren't quickly breaking down into ever-smaller nano-particles that can be absorbed into living things.
This is tangentially related to the article, but it's interesting that the phrase "unexpectedly stable" triggers positive connotations. It did for me as well.
But the phrase is actually neutral, it's not making any claims if stability is a good or bad thing in this context, neither about "unexpected" stability. But given the larger context of language we read it as positive.
Fission fragment rocket engines are also (theoretically) extremely efficient.. using the particles that come out of the reaction directly as a high-velocity exhaust stream.
Practical for many missions, just not for sending humans in person to other planets. For example, consider a mission to deliver a telescope out past 550AU so that it can use the whole sun as a gravitational lens. That’s more than 11× further than Pluto, but a fission fragment drive could get the telescope out there in about the amount of time it took New Horizons to fly past Pluto.
Yeah, thrust is thrust, there is no difference, really.
Only issue that I can think of is landing on a body with an atmosphere. In this case you might need to adjust for the bomb veing slowed by atmospheric on entry.
And also possibly adjust for any inhabitants trying to shoot you down before you try to land there with an Orion drive. ;-)
> A series of 50-kiloton bombs would be dropped into the cavern and exploded to heat the water and create steam. The steam would then power a secondary cooling loop for power extraction using a steam turbine. Dropping about two bombs a day would cause the system to reach thermal equilibrium, allowing the continual extraction of about 2 GW of electrical power
For some reason (that I haven’t figured out yet) thermonuclear bombs are just so much more efficient than any other proposed fission or fusion reaction.
It’s strange that controlled fusion is an energy sink, but whatever black magic is happening inside an H-bomb manages to unlock so much “free” energy.
Not really making nukes take a ridiculous amount of energy and you only get to use it once where the energy to create ITER gets split across its operating lifespan.
Further fission here requires a fission first stage which represents a huge additional energy input.
I really don’t trust that LLM estimate, they are really bad at that kind of thing but for the sake of argument let’s take that as a baseline.
ITER is supposed to be a 10-20x return on energy provided (10x being a basically guaranteed minimum) which means it may or may not be better depending on the specific bomb design, but it’s not massively better.
People talk about fusion as useless and slow but the current record holder in steady state was first turned on in 1983 and hit 0.67 in 1997. It’s not a failure of the underlying technology, it’s a near total lack of investment that’s stalled progress. ITER was started under the first Bush presidency and scaled back to a minimum design. It could have easily been built 20+ years ago if it was an actual priority.
If you want on of many direct quotes from them “DT-2 phase with the target to complete all project goals including the Q=10 project specification”. Guarantee may be a good little overstated, but Q=10 is a very pessimistic estimate.
Really the actual science bits are focused on the breeding blanket, remote operation, material science, etc hitting a high Q on DT doesn’t matter with the world’s supply of tritium so minimal. DEMO might be targeting Q=100, but that’s only useful if the tritium supply is sufficient and the timeline ends up way faster than starting in 1978 to only see a ~2033 first plasma.
> It could have easily been built 20+ years ago if it was an actual priority.
That is a bad thing to do. We diversified bets, and we end up finding a couple of pretty good energy sources, plus making some of the existing ones cleaner and safer.
Had we put all our money in fusion, today we might be drowning in cheap clean energy... or still living in a dirty coal-fuel environment, with a few old and dangerous fision reactors for lack of investment in development. A very risky bet.
I agree diversifying bets is a good idea, but building ITER 20 years ago wouldn’t have been a particularly significant investment.
Spend 1 billion/year (in today’s money) from 1987 and by 2006 you’re well past ITER’s projected cost back then there was little advantage to waiting. JET’s first plasma was 1983 so that’s another 10 years for design and 12 years for construction.
By comparison the US was spending ~12 Billion / year in energy R&D in 1978 (2026) dollars. That fell over time, but it’s not like total energy R&D spending couldn’t have increased vs historic levels. https://www.congress.gov/crs-product/RS22858
Even the cleanest bombs (97%+ fusion rather than fission) turned out to be too dirty for basically everything civilian (unlocking gas reservoirs - too radioactive; landscaping to replace enormous amounts of conventional explosives - too radioactive).
The efficiency is higher because the device is bigger. To oversimplify a bit, the surface area through which energy is radiated away grows slower than the volume containing the fuel. So heavier fuel "pellets" in bombs (ones in the kilogram to ton range) have a much easier time burning efficiently than the tiny milligram scale fuel pellets at NIF. Tiny fuel pellets cool down too fast. Likewise, multi-megaton fusion bombs are more efficient than the "little" sub-megaton bombs that the US favors (for reasons of compactness/deliverability) in its nuclear weapons stockpile.
Fusion is ridiculously efficient and effective power source. The problem with it is that it is very hard to created conditions where fusion can happen. The one reliable way we have that doesn't take more energy in than it outputs, is to detonate a fission bomb and use the x-rays to compress a fusion secondary.
The history of fusion research for the past 70 years is trying to figure out a cost-effective way to trigger enough fusion to make net energy without a nuke. So far, we've got bupkis. (The magnetic containment approaches using high-temperature superconductors seem promising, but we won't know they actually work until we've built them.)
> It’s strange that controlled fusion is an energy sink, but whatever black magic is happening inside an H-bomb manages to unlock so much “free” energy.
E=mc^2. The proportion of the original mass converted to energy in fusion is higher than it is for fission.
The trouble with fusion is that you need really high temperatures and pressures to sustain it. You can easily sustain a fission reaction at a few hundred degrees C, or even lower than that if you wanted to (but the general goal is to boil water to run a steam turbine so >100°C is what you want).
Fusion requires millions of degrees, which would vaporize most things you might want to use as a container, so instead they use strong magnetic fields and then you spend a lot of energy maintaining the magnetic field. A bomb doesn't care about that because sustained operation isn't required and vaporizing everything in the vicinity is kind of the idea.
Moreover, efficiency isn't really the issue. The efficiency of fission is already absurd. Fission of a given mass of uranium generates the same amount of energy as burning 2.7 million times that amount coal -- by mass, it's even more by volume.
The main advantages of fusion are that hydrogen is a lot more common than uranium (though uranium is still pretty available) and that the byproduct of fusion is helium (a non-radioactive noble gas with general usefulness), whereas some of the fission byproducts are variously radioactive or have limited known commercial applications.
Fusion is all about the 'triple product': pressure x temperature x time. The sun and nuclear bombs have plenty of pressure, but nuclear bombs don't operate for very long. Fusion reactors actually have a much lower pressure than the sun but correspondingly operate at much higher temperatures (about 10x what's in the core of the sun!).
Fission reactions shut down when the core expands enough to become subcritical. Boosting can help some, but most of the fissionable material will still fail to fission.
Thermonuclear assemblies don't have a chain reaction, so they can burn most of their fuel, once they get hot enough.
Not one of them... But were you talking about explosive assemblies or reactor assemblies? Cuz fission "reactor assemblies" going subcritical has very little to do with expansion in the long term, but rather with consumption of excess reactivity and buildup of poisons.
Also, you interestingly reminded me that fusion is unlike fission, the latter being a chain or cascading reaction (the self-sustaining kind), while former isn't (or is it? :M.Stevens face:)
The person I was responding to said "bombs", so I was talking about that. A fission bomb's chain reaction shuts down as soon as the assembly expands enough to become a bit subcritical. The thermonuclear bomb's hot burning fuel, on the other hand, continues to react (albeit at a slower rate) as it expands; there is no such sharp cutoff. The latter fact can be used to improve fission bombs some by "boosting": including a small amount of DT gas in the fission bomb, to provide a source of neutrons that induce some fission even after k drops below 1. If k is (say) 0.9, then each DT neutron will produce 10 fission events, for a large energy return, roughly 100x the energy from the fusion itself.
I'll add another observation: the secondary in a thermonuclear bomb is a lot like the target in inertial confinement fusion, only much larger. The expansion time of these systems is proportional to their radius, so if (say) the bomb has a million times the fuel, it takes 100 times longer to expand. So for a given density and temperature of fuel, there is 100x as much time for the fusion reactions to occur. In a real sense, thermonuclear bombs become easier to build as they get bigger.
We orbit a giant fusion energy source and capturing its energy has gotten pretty cheap. Not very efficient per se, but there's so much energy and it's free, so it doesn't matter.
Much safer than newly built reactors using decades old designs for making Plutonium used as power generators, with every safety feature forcefully disabled and during a drill to investigate the feasibility of a condition live, the effects of which weren’t known by any operator and the drill hadn’t been tested in an offline experiment before nor was it even simulated. Then, maybe.
"Stable" here means mechanically stable (they don't fall apart as quickly as was expected), not radiologically stable (the radioactive elements, of course, still decay at their normal rate).
Thank you! Geigerclickbate?
It’s phys.org
Of course it’s clickbait
The headline sounds weirdly positive... but it's "stable" as in [ed.: ecologically] "long-lived". Very much not a good thing.
For radionuclides more long-livd means less radioactive per unit of time, though. Of course uranium compounds can be toxic in the chemical sense as well, but I’m unsure if uranium compounds make it to the top threats in that list compared to e.g. arsenic and lead.
Of course radioactivity needs to be respected, and the exclusion zone is there for a reason due to factors such as hot spots.
This is "long-lived" in the ecological sense, not radiological. The grains of uranium oxide dust remain grains of uranium oxide dust, rather than breaking apart. If you ingest a few molecules of uranium oxide, it pretty much doesn't matter, you're fine¹. Ingest these dust particles, not so much. It's a question of concentration, and it seems that it's not diluting out naturally.
¹ humans contain, on average, 90µg of uranium. [https://www.iaea.org/sites/default/files/DU_Eng.pdf]
(P.S.: the radiological stability and lifetime of uranium doesn't make much sense to question; the dust flakes aren't large & concentrated enough to significantly shorten their half-life due to their own neutron emissions cascading and this isn't what the study was researching. Note the article talks about weathering: "It remains largely unclear why these particles weather at different rates in their environment.")
I think they mean that the fuel rods are not breaking down, aka leaching into the environment, as fast. That's a good thing.
It’s hard to call them “rods” at this point, since they melted and then cooled into tiny metallic droplets and shards after they were ejected in the explosion.
It means "mechanically stable", which could be either good or bad depending on the question, but is generally a limited good thing.
At the least, it means these particular compounds aren't quickly breaking down into ever-smaller nano-particles that can be absorbed into living things.
This is tangentially related to the article, but it's interesting that the phrase "unexpectedly stable" triggers positive connotations. It did for me as well.
But the phrase is actually neutral, it's not making any claims if stability is a good or bad thing in this context, neither about "unexpected" stability. But given the larger context of language we read it as positive.
is it possible to autoban/hide posts that intentionally go offtopic using dumb words like 'tangentially' as an excuse
40 years and counting, vs 1 year for Hiroshima
Basically, nuclear bombs are much safer than nuclear power plants.
next step: use nukes as an energy source
Some of the nuclear rocket propulsion ideas propose exactly that, like Project Orion.
If you like Orion check out Project Pluto (they even built some some test bench engines)
Fission fragment rocket engines are also (theoretically) extremely efficient.. using the particles that come out of the reaction directly as a high-velocity exhaust stream.
FFR have super high ISP but microscopic thrust. Not exactly practical.
Practical for many missions, just not for sending humans in person to other planets. For example, consider a mission to deliver a telescope out past 550AU so that it can use the whole sun as a gravitational lens. That’s more than 11× further than Pluto, but a fission fragment drive could get the telescope out there in about the amount of time it took New Horizons to fly past Pluto.
For that particular mission I’d be curious to compare to an ion drive architecture.
Don't ion drives consume comparitively a lot of xenon to work?
Yes, they have substantially lower specific impulse than fission fragment.
Production ion drives have ISPs between 1000s and 4000s (https://en.wikipedia.org/wiki/Ion_thruster#Comparisons). A fission fragment drive would have an estimated ISP of over 100,000s (https://www.nasa.gov/general/aerogel-core-fission-fragment-r...). Of course you can just buy an ion drive off the shelf, which is definitely an advantage. And making the fuel for a fission–fragment drive is probably going to be fun.
Not to mention needing a nuclear power source anyway, this far from the sun.
did they ever figure out how to brake? Spin the ship 180 degrees and bomb the front?
Couldn't you just turn and orbit ?
… without irradiating yourself?
Yeah, thrust is thrust, there is no difference, really.
Only issue that I can think of is landing on a body with an atmosphere. In this case you might need to adjust for the bomb veing slowed by atmospheric on entry.
And also possibly adjust for any inhabitants trying to shoot you down before you try to land there with an Orion drive. ;-)
Crazy sequence of words. I love it. ;)
Check out this 1970s project that proposed extracting electricity from thermonuclear explosions.
https://en.wikipedia.org/wiki/Project_PACER
> A series of 50-kiloton bombs would be dropped into the cavern and exploded to heat the water and create steam. The steam would then power a secondary cooling loop for power extraction using a steam turbine. Dropping about two bombs a day would cause the system to reach thermal equilibrium, allowing the continual extraction of about 2 GW of electrical power
"Hey boss, do you think there is a chance this scheme might introduce radioactive byproducts into the ground water?"
"Shut up"
Coming soon: thermonuclear fracking.
Already done https://en.wikipedia.org/wiki/Project_Gasbuggy
There goes another grant proposal into the bin...
Maybe you could make it work even better with PFAS added. Forever chemicals are forever!
In the end we're just boiling water.
There was also project Plowshare, as chronicled by Kurzgesagt at https://www.youtube.com/watch?v=h3DCdWyb0cc
Which was building canals etc with nuclear bombs. https://en.wikipedia.org/wiki/Project_Plowshare
I read Firecracker Boys and had lunch with the author! recommended
For some reason (that I haven’t figured out yet) thermonuclear bombs are just so much more efficient than any other proposed fission or fusion reaction.
It’s strange that controlled fusion is an energy sink, but whatever black magic is happening inside an H-bomb manages to unlock so much “free” energy.
Not really? How do you define efficiency here?
Thermonuclear bombs literally create lots of heat, and don’t tend to drive anything that produces work. It’s the opposite of efficient.
Just like lighting gasoline on fire and claiming that that’s more efficient than a combustion energy…
What if we used them to run Tesla turbines
I’m talking about net energy. Harnessing it is a whole different story.
Not really making nukes take a ridiculous amount of energy and you only get to use it once where the energy to create ITER gets split across its operating lifespan.
Further fission here requires a fission first stage which represents a huge additional energy input.
GPT pro says 3 to 30x energy release compared to the entire supply chain input for a megaton class weapon.
I trust the argument. You can look into it yourself. Long story short, it is massively energy positive compared to controlled fusion.
I really don’t trust that LLM estimate, they are really bad at that kind of thing but for the sake of argument let’s take that as a baseline.
ITER is supposed to be a 10-20x return on energy provided (10x being a basically guaranteed minimum) which means it may or may not be better depending on the specific bomb design, but it’s not massively better.
People talk about fusion as useless and slow but the current record holder in steady state was first turned on in 1983 and hit 0.67 in 1997. It’s not a failure of the underlying technology, it’s a near total lack of investment that’s stalled progress. ITER was started under the first Bush presidency and scaled back to a minimum design. It could have easily been built 20+ years ago if it was an actual priority.
Where did you find that ITER guaranteed 10x?
If you want on of many direct quotes from them “DT-2 phase with the target to complete all project goals including the Q=10 project specification”. Guarantee may be a good little overstated, but Q=10 is a very pessimistic estimate.
https://www.iter.org/fusion-energy/what-will-iter-do
Really the actual science bits are focused on the breeding blanket, remote operation, material science, etc hitting a high Q on DT doesn’t matter with the world’s supply of tritium so minimal. DEMO might be targeting Q=100, but that’s only useful if the tritium supply is sufficient and the timeline ends up way faster than starting in 1978 to only see a ~2033 first plasma.
> It could have easily been built 20+ years ago if it was an actual priority.
That is a bad thing to do. We diversified bets, and we end up finding a couple of pretty good energy sources, plus making some of the existing ones cleaner and safer.
Had we put all our money in fusion, today we might be drowning in cheap clean energy... or still living in a dirty coal-fuel environment, with a few old and dangerous fision reactors for lack of investment in development. A very risky bet.
I agree diversifying bets is a good idea, but building ITER 20 years ago wouldn’t have been a particularly significant investment.
Spend 1 billion/year (in today’s money) from 1987 and by 2006 you’re well past ITER’s projected cost back then there was little advantage to waiting. JET’s first plasma was 1983 so that’s another 10 years for design and 12 years for construction.
By comparison the US was spending ~12 Billion / year in energy R&D in 1978 (2026) dollars. That fell over time, but it’s not like total energy R&D spending couldn’t have increased vs historic levels. https://www.congress.gov/crs-product/RS22858
Even the cleanest bombs (97%+ fusion rather than fission) turned out to be too dirty for basically everything civilian (unlocking gas reservoirs - too radioactive; landscaping to replace enormous amounts of conventional explosives - too radioactive).
In order to trigger an H bomb, you first trigger a regular fission bomb to generate the necessary energy to trigger the second fusion stage.
So, fission bombs are the black magic.
I think there’s a lot more to it than that, like the heavy uranium tamper, “FOGBANK”, and radiation implosion (whatever that means).
It’s a much more efficient version of inertial confinement fusion like at the NIF.
The efficiency is higher because the device is bigger. To oversimplify a bit, the surface area through which energy is radiated away grows slower than the volume containing the fuel. So heavier fuel "pellets" in bombs (ones in the kilogram to ton range) have a much easier time burning efficiently than the tiny milligram scale fuel pellets at NIF. Tiny fuel pellets cool down too fast. Likewise, multi-megaton fusion bombs are more efficient than the "little" sub-megaton bombs that the US favors (for reasons of compactness/deliverability) in its nuclear weapons stockpile.
Fusion is ridiculously efficient and effective power source. The problem with it is that it is very hard to created conditions where fusion can happen. The one reliable way we have that doesn't take more energy in than it outputs, is to detonate a fission bomb and use the x-rays to compress a fusion secondary.
The history of fusion research for the past 70 years is trying to figure out a cost-effective way to trigger enough fusion to make net energy without a nuke. So far, we've got bupkis. (The magnetic containment approaches using high-temperature superconductors seem promising, but we won't know they actually work until we've built them.)
> It’s strange that controlled fusion is an energy sink, but whatever black magic is happening inside an H-bomb manages to unlock so much “free” energy.
E=mc^2. The proportion of the original mass converted to energy in fusion is higher than it is for fission.
The trouble with fusion is that you need really high temperatures and pressures to sustain it. You can easily sustain a fission reaction at a few hundred degrees C, or even lower than that if you wanted to (but the general goal is to boil water to run a steam turbine so >100°C is what you want).
Fusion requires millions of degrees, which would vaporize most things you might want to use as a container, so instead they use strong magnetic fields and then you spend a lot of energy maintaining the magnetic field. A bomb doesn't care about that because sustained operation isn't required and vaporizing everything in the vicinity is kind of the idea.
Moreover, efficiency isn't really the issue. The efficiency of fission is already absurd. Fission of a given mass of uranium generates the same amount of energy as burning 2.7 million times that amount coal -- by mass, it's even more by volume.
The main advantages of fusion are that hydrogen is a lot more common than uranium (though uranium is still pretty available) and that the byproduct of fusion is helium (a non-radioactive noble gas with general usefulness), whereas some of the fission byproducts are variously radioactive or have limited known commercial applications.
Fusion is all about the 'triple product': pressure x temperature x time. The sun and nuclear bombs have plenty of pressure, but nuclear bombs don't operate for very long. Fusion reactors actually have a much lower pressure than the sun but correspondingly operate at much higher temperatures (about 10x what's in the core of the sun!).
Fission reactions shut down when the core expands enough to become subcritical. Boosting can help some, but most of the fissionable material will still fail to fission.
Thermonuclear assemblies don't have a chain reaction, so they can burn most of their fuel, once they get hot enough.
I see some downvotes on that. Would any of the downvoters explain their objection, so I can address it?
Not one of them... But were you talking about explosive assemblies or reactor assemblies? Cuz fission "reactor assemblies" going subcritical has very little to do with expansion in the long term, but rather with consumption of excess reactivity and buildup of poisons.
Also, you interestingly reminded me that fusion is unlike fission, the latter being a chain or cascading reaction (the self-sustaining kind), while former isn't (or is it? :M.Stevens face:)
The person I was responding to said "bombs", so I was talking about that. A fission bomb's chain reaction shuts down as soon as the assembly expands enough to become a bit subcritical. The thermonuclear bomb's hot burning fuel, on the other hand, continues to react (albeit at a slower rate) as it expands; there is no such sharp cutoff. The latter fact can be used to improve fission bombs some by "boosting": including a small amount of DT gas in the fission bomb, to provide a source of neutrons that induce some fission even after k drops below 1. If k is (say) 0.9, then each DT neutron will produce 10 fission events, for a large energy return, roughly 100x the energy from the fusion itself.
I'll add another observation: the secondary in a thermonuclear bomb is a lot like the target in inertial confinement fusion, only much larger. The expansion time of these systems is proportional to their radius, so if (say) the bomb has a million times the fuel, it takes 100 times longer to expand. So for a given density and temperature of fuel, there is 100x as much time for the fusion reactions to occur. In a real sense, thermonuclear bombs become easier to build as they get bigger.
We orbit a giant fusion energy source and capturing its energy has gotten pretty cheap. Not very efficient per se, but there's so much energy and it's free, so it doesn't matter.
Solar is not effective in the outer solar system.
Let's worry about that once we get there.
Much safer than newly built reactors using decades old designs for making Plutonium used as power generators, with every safety feature forcefully disabled and during a drill to investigate the feasibility of a condition live, the effects of which weren’t known by any operator and the drill hadn’t been tested in an offline experiment before nor was it even simulated. Then, maybe.
Nuclear bombs are meant to go boom. Any part that doesn't go boom is waste whose weight could be better allocated to making it have a bigger boom.
> Nuclear bombs are meant to go boom
They're meant to go boom when told to. A good fraction of weapons engineering is around safety systems.
Places like Bikini Atoll are still heavily radiologically contaminated even though the tests ended in the 1950s, so not really.
190 tons of nuclear fuel, vs 64 kilograms.
172.4 tonnes*
It was a power plant full of fuel, why is this surprising?