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Comment by verdverm | Hacker News Reader

https://www.youtube.com/watch?v=zVhQOhxb1Mc has a good explanation of how nuclear weapons work.

It may be possible that a missel is disabled and when it hits the ground, produces a much lower yield explosion than designed for, in particular a plutonium device, if I recall the video and extrapolate with sufficient accuracy

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It is basically impossible for a plutonium bomb to generate anything resembling what you think of as a nuclear explosion unless it is deliberately triggered and experiences ideal ignition conditions.

If it were to crash into the ground, be blown up by an intercepting missile, or otherwise malfunction, you'll just get a normal-bomb-sized regular conventional explosion and a bunch of toxic and only mildly radioactive plutonium strewn all over the place.

Just adding about the so-called "dirty bombs" (https://en.wikipedia.org/wiki/Dirty_bomb). It's not dirty because it's lethal but rather because the construction of these bombs are rather crude, which allows nearly everyone with some knowledge of bomb building to construct them. In some sense, this is more dangerous than a proper fission-type nuclear bomb.

The explanation you gave for why a dirty bomb is called as such doesn't seem to be supported by the link you provided. Rather, it's dirty because it contaminates the area around the explosion with radioactive material.

That is not correct

The vast majority of effects of a dirty bomb are foiled by such advanced technologies as windows and showers. The initial conventional explosion will kill and injure far more people than the radioactive dust. At worst, that dust will slightly increase cancer rates for people relatively close to the location of the bomb (say, upto a few hundred meters) over their lifetime.

Dirty bombs are weapons of terror, not weapons of mass destruction.

The true damage is caused by societal and economic overreaction from the target: fear leads to expensive security theatre, a desire for vengeance leads to lashing out with expensive unnecessary wars, uncertainty and political instability destabilizes financial markets, etc.

Some diseases are similar: immune system overreaction causes more harm than the actual invader.

> It's not dirty because it's lethal but rather because the construction of these bombs are rather crude

I don’t think that’s correct, and do not see that Wikipedia page say that. It says

“The purpose of the weapon is to contaminate the area around the dispersal agent/conventional explosion with radioactive material, serving primarily as an area denial device against civilians.”

I think that “serving primarily as an area denial device against civilians.” isn’t 100% correct. For use by terrorists, I think it’s more to instill fear than to make areas inaccessible to civilians (that still would happen, but isn’t the goal)

Dirty bombs are typically not nuclear. They are just regular bombs packed with radioactive materials like medical grade cesium sources.

While plutonium is mildly radioactive than fission products like strontium-90 and cesium-137, you can't discount its chemical toxicity and will accumulate in the bone marrow if ingested. Also add that alpha decaying isotopes (like plutonium-239 used in bombs) elevates the risk for lung cancer when inhaled.[1]

Definitely a lot "better" than a nuclear explosion, but it's no picnic to have fragments of a destroyed nuclear warhead to be scattered around.

[1] https://en.wikipedia.org/wiki/Plutonium#Precautions

Yeah, it would not be anything like the explosion people think when they hear nuclear. What I recall from the video is that Plutonium is ~3x more reactive than Uranium, and if you brought two 2/3 critical mass together with your hands, they would explode the room you are in and create a lot of nasty dust.

I'm hypothesizing that a falling plutonium warhead might experience more kinetic energy on impact with the ground, such that the fissible material would still chain react, more so than the example given in the video of bringing them together with one's hands.

The amount of plutonium in a bomb is subcritical. There is no way a haphazard impact would cause it to go critical. It requires a very precisely timed explosion of the spherical lensed charges surrounding the core to generate an insane amount of implosive pressure which squeezes the core to be many factors more dense and therefore reach criticality.

...to have an ideal, optimized reaction that causes a large explosion. If you watched the video I linked in another comment, you would hear someone who knows more than both of us describe how other reactions happen and play out. There's a lot more to getting good, high yield nuclear explosions than you describe as well. I explicitly said that it would not be anything like a well done explosion, but there will still be nuclear chain reactions happening, they are always happening because of nuclear decay. It's a difference of how fast

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