Carnegie Mellon researchers Keith Florig and Baruch Fischhoff offer simple, practical advice: on whether it is worth citizens’ time to stock supplies needed for a home shelter, how urgently should one seek shelter following a nearby nuclear detonation, and how long should survivors remain in a shelter after the radioactive dust settles.
“A number of emergency-management organizations recommend that people stock their homes with a couple dozen categories of emergency supplies,” said Florig of Carnegie Mellon’s engineering and public policy department. “We calculated that it would cost about $240 per year for a typical family to maintain such a stock, including the value of storage space and the time needed to tend to it.”
Their research also suggests that many families who could afford to follow the stocking guidelines might think twice about whether the investment was really worth it, given the low probability that stocked supplies would actually be used in a nuclear emergency.
They advocate simple rules for minimizing risk based on how far people are from the blast. If you are within several miles of the blast, there will be no time to flee and you will have only minutes to seek shelter. If you are 10 miles [downwind] from the blast, you will have 15 to 60 minutes to find shelter, but not enough time to reliably flee the area before the fallout arrives,” said Florig.
However, the prior advice would suggest that if you are 10 miles from the blast that you could move perpendicular to the direction of the fallout plume and get out of the way in under 15 minutes. Needing to move one mile for smaller bombs. So I would think 10–20 miles downwind is a judgement call, but 25 miles you should be able to get out of the way of the fallout plume.