Michael Swanwick’s 1985 In the Drift is a stand-alone near-future alternate-history novel. In the Drift was the sixth1 novel in the Third Ace Science Fiction Specials series, edited by Terry Carr.
1979: in a spectacular exhibition of American nuclear industry know-how, Three Mile Island suffered a catastrophic melt-down. A vast swath of land downwind of the reactor was contaminated with radioactive debris. This is the so-called Drift. Millions fled, only to be violently murdered by their fearful fellow Americans. The USA splintered.
Almost a century later, the east coast is still a shambles but only some of it glows in the dark.