WW2 atomic bombing of Hiroshima & Nagasaki

[amcdonald]

A couple were made in the 1980's

Threads (1984) is the British effort about a nuclear attack on Sheffield.
The Day After (1983) is a US dramatization centring on Kansas City, IIRC.

Both can be found on YouTube.
Enjoy !

Who would bother to nuke Sheffield ?

[Churchill]

Who would bother to nuke Sheffield ?

Have you seen HSBC's data centre? It looks like it will withstand a direct hit.

[Mich the Tester]

Have you seen HSBC's data centre? It looks like it will withstand a direct hit.

No harm in trying.

[Bwana]

<deleted>

[RichardCranium]

How was it that they were able to rebuild & reinhabit Hiroshima within a few years of the bombing? I thought that radio-active half-life meant that a contaminated area would take decades or even centuries to become safe?

What a jolly good question. I have often wondered the same but never Googled it.

Very short:

Current exposure from residual radioactivity in both cities is actually far below that of naturally occurring background radiation. Almost 90% of the radioactivity was gone a week after the bombing, and the longest lasting radionuclide present in large enough quantities to cause concern (cesium-134) has a half-life of only two years.

Longer:

There are two ways radioactivity is produced from an atomic blast. The first is due to fallout of the fission products or the nuclear material itself, so directly uranium or plutonium that contaminate the ground.

The Hiroshima and Nagasaki bombs exploded at 500 to 600 m of altitude, then formed huge fireballs, thus producing the mushroom clouds of kicked-up debris that rose with the air currents. Since it rose, the material cooled down and started to fall as contaminated rain. Because of the wind at the time, the rain didn't fall directly on the hypocenter (the spot right beneath the detonation) but rather in the northwest region of Hiroshima (the Koi and Takasu areas), and the eastern region (Nishiyama area) of Nagasaki. Nowadays, the radioactivity is so miniscule that it's difficult to distinguish local "bomb"' radioactivity from the trace amounts of radioactivity caused by decades of atmospheric nuclear testing.

The other way that radioactivity is produced is by neutron irradiation of soil or buildings. In a normal weapon, neutrons are a maximum of 10% of a nuclear detonation, but they cause other, nonradioactive materials to become radioactive -- this is what people usually associate with the "thousands of years of radiation." The majority of the blast that doesn't come out as thermal radiation comes out as gamma-radiation, which is absolutely deadly within its given lethal radius, but dies down as an inverse-square law, and in any case, has nothing to do with making anything radioactive. They just go through one time, kill what they can, and then they're gone.

Even the neutron-irradiated material, however, decayed much more quickly than anyone thought, so quickly that only a few years after the war, American occupation troops could be stationed in those unfortunate cities without any rotation necessary at all to keep down their Rotgen count. Today, measuring the remnant neutron radioactivity takes months, even with 2010 technology.

In the end, the residual radioactivity is much less than the simple dose that every one of us receives walking around outside every day.

So that's it -- at the levels of radiation emitted by our nuclear weapons, it just wasn't enough to contaminate things.

Very Long: Hiroshima, Nagasaki and Subsequent Weapons Testing

[OwlHoot]

Just the neutrinos from a nuclear reaction can "activate" atomic particles, such as converting neutrons to protons, and thus transmute common elements like sodium and iron into radioactive isotopes.

Normally these are practically indetectable, and billions flit through our bodies every second almost without reacting. But problems start when the flux increases sufficiently ..

For example, if a supernova exploded within about 100 light years of the Solar System, we'd really be in the tulip for that reason among others

[AlfredJPruffock]

Just the neutrinos from a nuclear reaction can "activate" atomic particles, such as converting neutrons to protons, and thus transmute common elements like sodium and iron into radioactive isotopes.

Normally these are practically indetectable, and billions flit through our bodies every second almost without reacting. But problems start when the flux increases sufficiently ..

For example, if a supernova exploded within about 100 light years of the Solar System, we'd really be in the tulip for that reason among others

Well there is always Beltegeuse to keep you awake at night !

[d000hg]

Is it accurate to suppose that the weapons we could produce these days are of such scale that a single bomb could effectively wipe out a small (geographically) nation like England, say from London to Birmingham?

[TykeMerc]

Have you seen HSBC's data centre? It looks like it will withstand a direct hit.

That was designed to take direct hits. When it was built the IRA were threatening Midland Bank with all sorts of nasty stuff so that place was built to take a serious mortar attack. 90%+ of it is underground and the bit on the surface is sloped and ridged to deflect blast. The few windows are quadruple glazed and armoured. The loading bay doors would do justice to some of the military bunkers I've been in.
I was a frequent visitor there 20 years ago and my contact was part of the commissioning team when it was built, we discussed it while a tape restore was running.

[OwlHoot]

Is it accurate to suppose that the weapons we could produce these days are of such scale that a single bomb could effectively wipe out a small (geographically) nation like England, say from London to Birmingham?

I dare say a larger version of this could