But when they emerge they will have only the hell of the wastes to comfort them and the leadership of the Enclave to guide themIf we successfully take shelter for 30-80 years, there should be no issues in terms of nuclear fallout. While yes soot can cause the nuclear winter, it can also be caused by just an uplifting of light particles into the atmosphere, so blasting soil into the sky can give you a nuclear winter, but generally should be fine thanks to refrigeration, so long as foods have been stockpiled, as the nuclear winter probably will not last longer than 5 years.