"The Nuclear Regulatory Commission is approaching completion of an ambitious study that concludes that a meltdown at a typical American reactor would lead to far fewer deaths than previously assumed."
However, "the study assumed a successful evacuation of 99.5 percent of the people within 10 miles, for example. The report also assumes 'average' weather conditions" as noted by Edwin Lyman of UCS. The New York Times
As the Fukushima disaster has clearly demonstrated, nearly perfect evacuation is impossible and radiation does not deposit in concentric circles radiating out from the plant, but rather, follows the weather.