Alot of variables. Depends on how many/much rads and roentgens (sp?) are absorbed at what rate for how long, bomb/event yield, how close. The potassium iodide tablets could be agood idea if you lived in a big (target) city, or near a nuke plant. I'm not an expert, just kind of going by memory of NBC training so many years ago. Unless within 50 miles of an event within your parameters, I don't think I'd worry much.