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.
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.
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 slow 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.
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).
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[ 5.9 ms ] story [ 94.9 ms ] threadOf course radioactivity needs to be respected, and the exclusion zone is there for a reason due to factors such as hot spots.
¹ humans contain, on average, 90µg of uranium. [https://www.iaea.org/sites/default/files/DU_Eng.pdf]
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.
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.
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. ;-)
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
"Shut up"
Which was building canals etc with nuclear bombs. https://en.wikipedia.org/wiki/Project_Plowshare
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.
So, fission bombs are the black magic.
It’s a much more efficient version of inertial confinement fusion like at the NIF.
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.)
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.
Thermonuclear assemblies don't have a chain reaction, so they can burn most of their fuel, once they get hot enough.
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:)
They're meant to go boom when told to. A good fraction of weapons engineering is around safety systems.
The contamination created by Chernobyl is especially long-lived, not because of the amount of fuel.
Of course it’s clickbait