I’ve heard people say there is no fallout, but there typically is a fission bomb in the secondary stage. Where does its radiation go? Is it just blown away by the fusion bomb so it’s no longer as deadly? Isn’t it still there though? Is it just weaker?
In: Physics
Yes they do produce fallout. The most important difference between an Atomic Bomb (fission) and a Hydrogen Bomb (fusion) is simply efficiency. Fusion produces far more energy relative to its fuel than fission, by as much as 1000x.
Fusion also produces somewhat more ionizing radiation relative to the actual heat and explosive force so it kills people while doing less damage to buildings and other infrastructure but the reason it produces less fallout and lingering radiation is because there’s much much less radioactive material required to produce a comparably deadly blast.
Yes. Fallout mostly doesn’t come from the bomb, it comes from neutrons the bomb releases interacting with material thrown up by the explosion.
I will break this down in two parts. First the trigger (primary) and second the hydrogen bomb (secomdary) part.
The “spark” primary to the hydrogen bomb is an atomic bomb it consists of either enriched uranium or plutonium (or a mix) and splits atoms giving off energy. You need this oo generate tremendous heat and pressure.
The “plug” secondary is the cylindrical part, it consists of a radiation case, some foam or plastic and a some hydrogen. There also is uranium to first be energized by x rays then emit neutrons. The neutron combines with the hydrogen and helium is formed. So a pure fusion weapon does not have plutonium and only creates helium… but it doesn’t exist because the secondary needs the pressure and heat of the sun to fuse elements. As it fuses and becomes helium it gives off tremendous energy.
A well working fission bomb already have very little fallout. If the device works as designed then all fission material gets converted to stable isotopes. It is when the detonation does not go as planned that you get large amounts of half-fissioned material that forms the radioactive fallout. This is generally why some test sites became contaminated while others were not.
I am not quite sure what effects a fusion reaction have on this though. I would presume that the fusion detonation could eliminate some of the fallout from the fission reaction by bombarding it with neutrons. It is also not quite right that fusion reactions have no fallout. Similar to a fission bomb in a perfect scenario all the material end up as stable helium but where things are not perfect you can get radioactive tritium or isotopes of lithium and other elements. And the neutrons can create a lot of radioactive elements in the material around the bomb.
In any way the amount of fallout from a hydrogen bomb compared to its yield is a lot lower, almost negligible. But it does suffer from the same issue as atom bombs in that failed tests can still have considerable fallout.
They can be relatively clean(never perfectly clean), or extremely dirty. Depends on detonation altitude and what the secondary tamper is made out of. The fusion releases a lot of neutrons, and this can be used to split depleted uranium, which increases yields but is also very dirty.
With an airburst the contamination is only the material the bomb is made of, and it’s so finely divided that it takes weeks to fall out of the atmosphere, by which point the worst isotopes have already decayed and the rest have been diluted. With a ground level detonation, a lot of relatively heavy material gets contaminated and falls out of the air nearby, posing an immediate hazard.
It produces more fallout. A hydrogen bomb is two bombs in one. The first is a plutonium device that acts as a spark to create massive amounts of heat and pressure quickly to kick off the second part, which is the fusion of the hydrogen. And that hydrogen part usually uses a lot of uranium as part of its construction. So, even though much of the explosive energy comes from the fusion of hydrogen, there is still fallout produced from the fissioning of uranium and plutonium.
Fall Out is produced, not only by the explosion, but by the things the explosion destroys like buildings, ground, fluid, etc… They become dust and steam. These things mix with the radiation and the shock wave distributes it.
Simple answer, yes. A hydrogen bomb contains a regular fission bomb inside it as the trigger to start the fusion reaction.
More complicated answer, not as much. A modern hydrogen bomb has a much higher yield but only the fission primary produces fallout and that fission primary is extremely small because modern designs are more efficient compared to designs from the 40s so you’ll end up with maybe 10x less fallout and 10x more explosive power.
Fusion bombs aren’t just hydrogen isotopes fusing..
To start with the current way we can start the fusion reaction is to use a fission atomic bomb. So you have a uranium/plutonium bomb in the assembly just to get the thing going.
Following – in a lot of hydrogen bombs the fusion stage is also used to generate a sea of fast moving neutrons that is absorbed by fissile material surrounding the fusion core (and enabling the fusion core to fuse) and results in even more fission than you’d get from a plain fission bomb that blows itself apart before all that much fission can take place.
So yes, hydrogen bombs very much cause fallout.
The majority of the yield from most hydrogen devices comes from fission of the uranium tamper. They just include fusion, they’re not primarily fusion.
They still produce fallout, and likely a lot more than some pure fission bombs. It’s possible to reduce fallout (Tsar Bomba detonated without the tamper and was something like 97% fusion), but it would dramatically reduce the yield (50% in this case).
Latest Answers