According to the book, a big risk is "skyshine": gamma radiation from the decay of radioactive particles that get spread into the atmosphere. Concrete walls ar

According to the book, a big risk is "skyshine": gamma radiation from the decay of radioactive particles that get spread into the atmosphere. Concrete walls are pretty good, and being underground is pretty good, but the problem with basements is that the materials above you that most houses are made of aren't terribly effective at blocking gamma radiation. So, even in a basement you'd still want to get under some thick/dense materials if you can. I hope this information does not ever come in handy.