virtualguy92107
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Fallout would in general be "reasonable safe" after a few weeks, and you would check the radiation strength before venturing outside. Returning to close to background levels would take decades at least.
Quadrillian
There is no easy answer to this because the danger from radiation depends upon the type of radiation and the lenth of exposure. On a sunny day you would probably burn in ten minutes, but on a cloudy day it might take twice that long becasue the clouds attenuate some of the UV from the sun. Get the idea.
Not only that but even if you do burn, the lethal dose of UV will depend on the depth of the burn and even then you only get an estimate of your chances of survival.
So with fallout the main risk is in the intensity of the radiation and the length of exposure time. The nearer you are to a criticality event (I assume that's what you mean) which releases fallout the heavier will be the intensity of radiation from the fallout. Note that wind direction will also have a strong effect on the fallout pattern.
Assuming your only problem is the fallout and you did not receive a dose of direct radiation from the event, then your risk will depend upon exposure time and time since the event, as the fallout decays over time. You really should look up tables on this, they are available on the internet, and if you are genuinely concerned you should purchase a radiation meter that is designed for the purpose and measures radiation in REMs.
Radiation damage is cumulative at higher doses and a dose of 600REMs will generally be lethal. SO if the ambient radiation read 1200REMs/hour you could expect to survive if you were only exposed for a few minutes. A half an hour and you would be in real trouble.
Generally it is thought that after two weeks the radiation will have eased to the point where you could take short daily excursions into the radiation field, but really it is impossible to be more specific without actual measurements.
Cheers!
busterwasmycat
doesn't really work that way. energy intensities are different, so a small dose of a high energy source is a lot more damaging than a longer dose of lower energy radiation. Most of the sun's energy that we receive is fairly low energy because of atmospheric filtering and absorption (which is why flying involves so much more exposure per unit time than being on the ground) and the nature of the emission spectrum from the sun. On top of that, the main problem of exposure with fallout is a proximity issue (and largely an ingestion or inhalation issue). Hard to compare the two.
It also depends on how much fallout there actually is (would be). more mass means more emissions per unit time. 10 bombs will produce ten times the fallout per unit area than one bomb, say. Thus it will take longer for that ten-bomb fallout to get to the same low level of emission intensity per unit time as it would take fallout from one bomb.
I have read that we are looking at something like 3-6 months to get broad emissions back to acceptable levels (a lot of the decay will be pretty rapid and that rapid decay will be the stuff producing the energy that "burns" or kills). There will still be hot spots and longer lived isotopes that could be eaten or inhaled, though, even if the general radiation intensity got back to near acceptable levels. the main problem after a few months would not be baking in a radiation glow after a few minutes or hours, but the dangers of ingestion and inhalation of radioactive isotopes would remain for a lot longer, many years for some elements. It would be hard to avoid exposure when a lot of the isotopes would get incorporated into the food chain.
?
It depends is the irritating answer.
An air burst produces little fall out and almost all of it short term. A ground burst produces a LOT of extremely nasty fall-out a large part of it is long term.
But long term = lower dose now.
Every nuke produces a plume that goes down wind. If you are NOT downwind then you are pretty safe initially. YOu have to survive the nuclear winter, the collapse of ALL services, an elevated cancer rate from the end products.