Russia has the largest haul of nuclear weapons of any country in the world and reportedly has the most powerful bomb named the SS-18 – menacingly nicknamed the Satan. A staggering 112.6million people could be at risk of extermination from the deadly missiles. Experts estimate Russia has 55 of the deadly weapons, but only five would be needed to destroy the East Coast of the US. The atomic bombs dropped on Hiroshima and Nagasaki would look like “popguns” in comparison to the demolition the Satan missiles could inflict. Dr Paul Craig Roberts, who served under Ronald Reagan administration, claimed the bombs would "wipe out three quarters of New York state for thousands of years”
Where are these people getting their information?
Even so.. The circle is the maximum blast radius ( beyond which you won't even get burned) - and its of a similar size to this 20 Megaton Payload if all 10 800kt warheads hit in the same place... but these are the 80's missiles that are way past their shelf life. http://www.atomicarchive.com/Docs/Effects/wenw_chp2.shtml
Yeah, The fallout could get 3/4 of New York State, but 1000 years? No.
Probably the most serious threat is cesium-137, a gamma emitter with a half-life of 30 years. It is a major source of radiation in nuclear fallout, and since it parallels potassium chemistry, it is readily taken into the blood of animals and men and may be incorporated into tissue. Other hazards are strontium-90, an electron emitter with a half-life of 28 years, and iodine-131 with a half-life of only 8 days. Strontium-90 follows calcium chemistry, so that it is readily incorporated into the bones and teeth, particularly of young children who have received milk from cows consuming contaminated forage. Iodine-131 is a similar threat to infants and children because of its concentration in the thyroid gland. In addition, there is plutonium-239, frequently used in nuclear explosives. A bone-seeker like strontium-90, it may also become lodged in the lungs, where its intense local radiation can cause cancer or other damage. Plutonium-239 decays through emission of an alpha particle (helium nucleus) and has a half-life of 24,000 years. To the extent that hydrogen fusion contributes to the explosive force of a weapon, two other radionuclides will be released: tritium (hydrogen-3), an electron emitter with a half-life of 12 years, and carbon-14, an electron emitter with a half-life of 5,730 years. Both are taken up through the food cycle and readily incorporated in organic matter...
So yes, you MUST get out of the path of fallout - but depending on the concentrations of Strontium and Cesium isotopes, you could probably live safely there within a couple of years ..
Just a reminder, there are people living in Hiroshima and Nagasaki today. Those were air bursts and most of the radioactive crap blew out and was scattered over a wider area. http://www.telegraph.co.uk/news/worldnews/asia/japan/11784827/70-years-after-the-atomic-bombs-Hiroshima-and-Nagasaki-then-and-now.html?frame=3398248
But Chernobyl was a meltdown - direct soil contamination and Animals and even some of the original residents - have returned to Chernobyl. http://www.telegraph.co.uk/news/2016/04/23/wildlife-returns-to-radioactive-wasteland-of-chernobyl/
The point is the after effects are not immediately lethal. Will you probably eventually die of cancer? Sure. But that could take decades.
I doubt either side is really planning on using ground bursts in an attack - its far, far too messy. Even so - we have already put 500 MEGTONS of nuclear ash into the atmosphere since the bomb was invented.
A U.N. scientific committee has estimated that the cumulative per capita dose to the world's population up to the year 2000 as a result of atmospheric testing through 1970 (cutoff date of the study) will be the equivalent of 2 years' exposure to natural background radiation on the earth's surface. For the bulk of the world's population, internal and external radiation doses of natural origin amount to less than one-tenth rad annually. Thus nuclear testing to date does not appear to pose a severe radiation threat in global terms. But a nuclear war releasing 10 or 100 times the total yield of all previous weapons tests could pose a far greater worldwide threat. The biological effects of all forms of ionizing radiation have been calculated within broad ranges by the National Academy of Sciences. Based on these calculations, fallout from the 500-plus megatons of nuclear testing through 1970 will produce between 2 and 25 cases of genetic disease per million live births in the next generation.
This means that between 3 and 50 persons per billion births in the post-testing generation will have genetic damage for each megaton of nuclear yield exploded. With similar uncertainty, it is possible to estimate that the induction of cancers would range from 75 to 300 cases per megaton for each billion people in the post-test generation.
If we apply these very rough yardsticks to a large-scale nuclear war in which 10,000 megatons of nuclear force are detonated, the effects on a world population of 5 billion appear enormous. Allowing for uncertainties about the dynamics of a possible nuclear war, radiation-induced cancers and genetic damage together over 30 years are estimated to range from 1.5 to 30 million for the world population as a whole. This would mean one additional case for every 100 to 3,000 people or about 1/2 percent to 15 percent of the estimated peacetime cancer death rate in developed countries. As will be seen, moreover, there could be other, less well understood effects which would drastically increase suffering and death.
And the peacetime cancer rate in the United States is 454.8 per 100,000. So a Full scale Nuclear exchange would add at worst 1000 to that number for the survivors born into that new world. Humans and Animals were born under a giant Fusion explosion going ton 100% of the time. Yes we have atmosphere as shielding, but the fact of the matter is, your body was built to withstand being irradiated to some extent. The only reason Cancer is the killer it is is because modern medicine has pretty much eliminated most of the other stuff. Now post Nuclear war, there probably won't be modern medicine tro the degree with have it now ( or even post Obamacare) and surival is hard work - and that means other injuries. Could cancer inducing radiation kill you after a nuclear war, sure. Its far more likely however it will be that infected cut you got harvesting or pneumonia after a cold.