Kate Sheppard debates the question:

The Nuclear Regulatory Commission (NRC) currently sets the evacuation zone around American nuclear power plants, also known as the "Plume Exposure Pathway Emergency Planning Zone," at 10 miles. Japanese authorities have evacuated residents living within about 19 miles of the damaged Fukushima Daiichi Nuclear Power Plant. But US officials have urged all Americans within 50 miles of the troubled Japanese reactors to get out of the way. ...

Widening the evacuation zones to 50 miles around the United States' 104 plants would affect a number of densely populated areas. The Indian Point zone would, of course, then include all of New York City—meaning that the 21 million people in the 50-mile radius might need to relocate in case of a serious emergency. Maryland's Calvert Cliffs Nuclear Power Plant is nearly 50 miles from Washington, DC, home to 500,000. The McGuire Nuclear Station is just 17 miles from Charlotte, North Carolina, which has 730,000 residents.