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Is radioactive fallout from a thermo-nuclear weapon an important consideration (compared to the destruction of the "thermo" part)? The bombs dropped in Japan on

Is radioactive fallout from a thermo-nuclear weapon an important consideration (compared to the destruction of the "thermo" part)? The bombs dropped in Japan only contained a few kg of fissile material, those cities were rebuilt within years. Modern bombs are probably way bigger, but even a W78 warhead comes in at only 120 kg or so and I'm guessing most of that is not plutonium. Compare this to the thousands of tons of radioactive or activated material that flew around Europe following the steam explosion at Chernobyl.

arethuza 5y ago
According to Daniel Ellsberg the only thing considered by US planners was blast yield - fallout and direct radiation (particularly thermal effects) were ignored as their effects were regarded as too unpredictable. This was in the 1960s though - things may have changed. edit: Fall out, even with modern weapons, would be a huge consideration if you are downwind of a target likely to be hit by a surface burst. You can experiment on Nukemap with the different options: https://nuclearsecrecy.com/nukemap/ https://nuclearsecrecy.com/nukemap/
- CapitalistCartr 5y ago
  It hadn't in the Eighties. If you want to be a nuclear war planner, I suggest Nukemap. https://nuclearsecrecy.com/nukemap/ https://nuclearsecrecy.com/nukemap/ No more plastic wheels to spin like a sliderule. Want to take out a target? What's your weapon system's CEP (Circle of Equal Probability)? How is the target built, that is, how much overpressure to destroy it, and how deeply buried is it? Now choose a weapon. If it'a high-priority target, aim more than one weapon at it.
caf 5y ago
The fallout by mass isn't primarily the direct daughter products of the fission. It's the thousands of tonnes of pulverised dirt and rock (and concrete and steel and...) that has been neutron-activated and ejected high into the atmosphere.
- refurb 5y ago
  This was my understanding as well. Radiation levels of daughter products from the weapon drop quite quickly. But the dirt that’s been neutron activated can take a while to come back down and the exposure levels are much higher.

arethuza 5y ago

According to Daniel Ellsberg the only thing considered by US planners was blast yield - fallout and direct radiation (particularly thermal effects) were ignored as their effects were regarded as too unpredictable. This was in the 1960s though - things may have changed. edit: Fall out, even with modern weapons, would be a huge consideration if you are downwind of a target likely to be hit by a surface burst. You can experiment on Nukemap with the different options: https://nuclearsecrecy.com/nukemap/ https://nuclearsecrecy.com/nukemap/

CapitalistCartr 5y ago
It hadn't in the Eighties. If you want to be a nuclear war planner, I suggest Nukemap. https://nuclearsecrecy.com/nukemap/ https://nuclearsecrecy.com/nukemap/ No more plastic wheels to spin like a sliderule. Want to take out a target? What's your weapon system's CEP (Circle of Equal Probability)? How is the target built, that is, how much overpressure to destroy it, and how deeply buried is it? Now choose a weapon. If it'a high-priority target, aim more than one weapon at it.

caf 5y ago

The fallout by mass isn't primarily the direct daughter products of the fission. It's the thousands of tonnes of pulverised dirt and rock (and concrete and steel and...) that has been neutron-activated and ejected high into the atmosphere.

refurb 5y ago
This was my understanding as well. Radiation levels of daughter products from the weapon drop quite quickly. But the dirt that’s been neutron activated can take a while to come back down and the exposure levels are much higher.