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They refer to it as a "clean" bomb and let people walk around at the hypocenter immediately afterward, saying the radiation measured was insignificant. How is t

They refer to it as a "clean" bomb and let people walk around at the hypocenter immediately afterward, saying the radiation measured was insignificant. How is this possible? Is this a common feature of hydrogen bombs?

totetsu 6y ago
It's a propaganda film. (Later surrounding countries complained about fallout, and atmospheric testing was replaced by underground testing)
- hinkley 6y ago
  I was appalled to learn that nuclear weapons testing roughly doubles the radiation exposure of a person living at sea level (the atmosphere blocks a lot from outer space).
tyingq 6y ago
I can't vouch for it personally, since I have no expertise there, but this Quora answer sounds credible: https://www.quora.com/How-did-they-minimize-the-radiation-of-Tsar-Bomba https://www.quora.com/How-did-they-minimize-the-radiation-of... Basically lead instead of uranium tampers. Makes for more fusion, less fission.
Barrin92 6y ago
Well clean is relative. Hydrogen bombs still have a traditional fission stage and that is going to produce fallout. However the bomb was detonated several kilometers above ground which means that fallout would generally be dispersed widely downwind from the source of the explosion. I'm not a 100% sure but it certainly might have been possible that the location wasn't very radioactive afterwards.
hinkley 6y ago
I've I've parsed this properly: https://en.wikipedia.org/wiki/Thermonuclear_weapon https://en.wikipedia.org/wiki/Thermonuclear_weapon A hydrogen bomb is triggered by a smaller plutonium/depleted uranium device. It's the moral equivalent of a detonator for C4, with a sprinkle of X-Rays and plasma on the side. The punchline is about a third of the way down: > The fission reactions though, especially the last fission reactions, release a tremendous amount of fission products and fallout. If the last fission stage is omitted, by replacing the uranium tamper with one made of lead, for example, the overall explosive force is reduced by approximately half but the amount of fallout is relatively low. The neutron bomb is a hydrogen bomb with an intentionally thin tamper, allowing most of the fast fusion neutrons as possible to escape.
- rsynnott 6y ago
  That's exactly what was done here. They actually tested the cut-down version; with a uranium tamper it might have been over 100MT.
- almost_usual 6y ago
  > Khrushchev wanted a 100 megaton weapon and to achieve such size, the engineers added a third stage on the thermonuclear warhead. Normal hydrogen bombs comprise two stages. Understanding the extreme radiation releases, the engineers, and among them Andrei Sakharov, decided to reduce the actual yield of 100 megatons to around half.
mLuby 6y ago
26:13 "Before landing the [radiation reconnaissance] helicopter – a check for radioactivity. Even in the very centre of the site, it was insignificant."
jfb 6y ago
It's a piece of internal Soviet propaganda. Draw your own conclusions.
- jbay808 6y ago
  Despite the cheery orchestral music, I don't think a video that was classified for 60 years would have been produced as propaganda. I assume it was intended as an internal technical report for high-ranking officials.
  - yencabulator 6y ago
    They had internal propaganda too. Just like all US military produced World War 2 era documentary and training films describe the conditions as downright cheery.
    - sudosysgen 6y ago
      Internal propaganda is not classified. This was most likely a documentary to inform decision makers.
      - jfb 6y ago
        There isn't really a distinction to be drawn between "a documentary to inform decision makers" and "propaganda". Everybody in the Soviet Union was lying to everyone else -- they were responding rationally to the incentives they were presented with.
rsynnott 6y ago
It was cleaner than most fusion bombs, and fairly high up, so it probably wasn't _too_ bad on the ground. Also their attitudes would have been different. There were hundreds of atmospheric tests in those couple of decades.
AngryData 6y ago
Most of the nuclear fallout on a nuclear explosion is from detonating at or near ground level which turns the dirt and dust around there radioactive while blasting it high into the air. An air burst bomb only has the radioactive material that failed to explode in the bomb, and like someone else mentioned that is easy to deal with and isn't a real big problem in the first place unless you intentionally are making your bomb inefficient and dirty.
Tuna-Fish 6y ago
Two-stage nuclear weapons get cleaner as they get bigger, because the excess neutrons from the second stage will destroy any long-lived fission products from the first stage. On top of that, all you need is a tamper that doesn't get activated by neutrons and you can push the fallout down to insignificance. This is why "atoms for peace" and such initiatives were not quite as stupid as they sound at the outset, as it would have been possible to build bombs that don't cause much fallout for them. However, since you can roughly double the power of any two-stage bomb by replacing the tamper with uranium, at minimal expense and with no added mass, but at the cost of producing massive amounts of fallout, real bombs deployed for war generally would have made a lot of fallout.
- Symmetry 6y ago
  That's all true of bombs detonated high up in the air where the only elements around are hydrogen, oxygen, nitrogen, carbon, and argon - none of which tend to be neutron activated in a particularly dangerous way. On the ground if you're using bombs for engineering work there are a lot of other elements that do get very upset if you hit them with fusion neutrons. Even in the context of 3 stage designs there's a huge difference in fallout between airbursts and groundbursts. It's the groundburst fallout that would have killed everyone in Copehagen and Stockholm if WWIII had gone down when the wind was blowing from the east, even with a successful US first strike.
nabla9 6y ago
There are two types of fallout: local and global fallout. Airburst creates relatively little or no local radioactive fallout relative to groundburst. Only fission is always dirty. Hydrogen bomb can be made clean, dirty or extremely dirty (salted) depending on the tamper material. Also, underwater explosions of hydrogen bomb create dirty explosion due to natrium in the water. Need for fission reaction to start the fusion reacton creates always some radioactive particles. Tzar bomba was airburst hydrogen bomb with lead tamper. It was relatively clean but the fission core still crated global fallout.

totetsu 6y ago

It's a propaganda film. (Later surrounding countries complained about fallout, and atmospheric testing was replaced by underground testing)

hinkley 6y ago
I was appalled to learn that nuclear weapons testing roughly doubles the radiation exposure of a person living at sea level (the atmosphere blocks a lot from outer space).

tyingq 6y ago

I can't vouch for it personally, since I have no expertise there, but this Quora answer sounds credible: https://www.quora.com/How-did-they-minimize-the-radiation-of-Tsar-Bomba https://www.quora.com/How-did-they-minimize-the-radiation-of... Basically lead instead of uranium tampers. Makes for more fusion, less fission.

Barrin92 6y ago

Well clean is relative. Hydrogen bombs still have a traditional fission stage and that is going to produce fallout. However the bomb was detonated several kilometers above ground which means that fallout would generally be dispersed widely downwind from the source of the explosion. I'm not a 100% sure but it certainly might have been possible that the location wasn't very radioactive afterwards.

hinkley 6y ago

I've I've parsed this properly: https://en.wikipedia.org/wiki/Thermonuclear_weapon https://en.wikipedia.org/wiki/Thermonuclear_weapon A hydrogen bomb is triggered by a smaller plutonium/depleted uranium device. It's the moral equivalent of a detonator for C4, with a sprinkle of X-Rays and plasma on the side. The punchline is about a third of the way down: > The fission reactions though, especially the last fission reactions, release a tremendous amount of fission products and fallout. If the last fission stage is omitted, by replacing the uranium tamper with one made of lead, for example, the overall explosive force is reduced by approximately half but the amount of fallout is relatively low. The neutron bomb is a hydrogen bomb with an intentionally thin tamper, allowing most of the fast fusion neutrons as possible to escape.

rsynnott 6y ago
That's exactly what was done here. They actually tested the cut-down version; with a uranium tamper it might have been over 100MT.
almost_usual 6y ago
> Khrushchev wanted a 100 megaton weapon and to achieve such size, the engineers added a third stage on the thermonuclear warhead. Normal hydrogen bombs comprise two stages. Understanding the extreme radiation releases, the engineers, and among them Andrei Sakharov, decided to reduce the actual yield of 100 megatons to around half.

mLuby 6y ago

26:13 "Before landing the [radiation reconnaissance] helicopter – a check for radioactivity. Even in the very centre of the site, it was insignificant."

jfb 6y ago

It's a piece of internal Soviet propaganda. Draw your own conclusions.

jbay808 6y ago
Despite the cheery orchestral music, I don't think a video that was classified for 60 years would have been produced as propaganda. I assume it was intended as an internal technical report for high-ranking officials.
- yencabulator 6y ago
  They had internal propaganda too. Just like all US military produced World War 2 era documentary and training films describe the conditions as downright cheery.
  - sudosysgen 6y ago
    Internal propaganda is not classified. This was most likely a documentary to inform decision makers.
    - jfb 6y ago
      There isn't really a distinction to be drawn between "a documentary to inform decision makers" and "propaganda". Everybody in the Soviet Union was lying to everyone else -- they were responding rationally to the incentives they were presented with.

rsynnott 6y ago

It was cleaner than most fusion bombs, and fairly high up, so it probably wasn't _too_ bad on the ground. Also their attitudes would have been different. There were hundreds of atmospheric tests in those couple of decades.

AngryData 6y ago

Most of the nuclear fallout on a nuclear explosion is from detonating at or near ground level which turns the dirt and dust around there radioactive while blasting it high into the air. An air burst bomb only has the radioactive material that failed to explode in the bomb, and like someone else mentioned that is easy to deal with and isn't a real big problem in the first place unless you intentionally are making your bomb inefficient and dirty.

Tuna-Fish 6y ago

Two-stage nuclear weapons get cleaner as they get bigger, because the excess neutrons from the second stage will destroy any long-lived fission products from the first stage. On top of that, all you need is a tamper that doesn't get activated by neutrons and you can push the fallout down to insignificance. This is why "atoms for peace" and such initiatives were not quite as stupid as they sound at the outset, as it would have been possible to build bombs that don't cause much fallout for them. However, since you can roughly double the power of any two-stage bomb by replacing the tamper with uranium, at minimal expense and with no added mass, but at the cost of producing massive amounts of fallout, real bombs deployed for war generally would have made a lot of fallout.

Symmetry 6y ago
That's all true of bombs detonated high up in the air where the only elements around are hydrogen, oxygen, nitrogen, carbon, and argon - none of which tend to be neutron activated in a particularly dangerous way. On the ground if you're using bombs for engineering work there are a lot of other elements that do get very upset if you hit them with fusion neutrons. Even in the context of 3 stage designs there's a huge difference in fallout between airbursts and groundbursts. It's the groundburst fallout that would have killed everyone in Copehagen and Stockholm if WWIII had gone down when the wind was blowing from the east, even with a successful US first strike.

nabla9 6y ago

There are two types of fallout: local and global fallout. Airburst creates relatively little or no local radioactive fallout relative to groundburst. Only fission is always dirty. Hydrogen bomb can be made clean, dirty or extremely dirty (salted) depending on the tamper material. Also, underwater explosions of hydrogen bomb create dirty explosion due to natrium in the water. Need for fission reaction to start the fusion reacton creates always some radioactive particles. Tzar bomba was airburst hydrogen bomb with lead tamper. It was relatively clean but the fission core still crated global fallout.