When American Airlines Flight 11 flew at low altitude down the Hudson River valley on the morning of Sept. 11, 2001, its target was the north tower of the World Trade Center. But its impact is still being felt at a cluster of buildings it passed about five minutes before it reached lower Manhattan, at a nuclear-reactor complex called Indian Point in Buchanan, NY. Adjacent to the site's two operating reactors are two buildings packed with highly radioactive spent-fuel rods, in pools of water 12 meters deep and tinged Ty-D-Bol blue by boron added to tamp down nuclear chain reactions. The soothing hum of the pumps that circulate the building's warm, moist air -- and, critically, keep the water cool -- lends an atmosphere of industrial tranquility.

Without that cooling water, the fuel cladding might overheat, melt, catch fire, and release radiation. Whether the impact of a Boeing 767 like Flight 11 could drain one of the pools and disable backup water pumps, starting such a fire, is far from clear. Nevertheless, the threat of terrorism in general and the flyover of Flight 11 in particular have reignited the debate about why all of this dangerous fuel is still here -- indeed, why all spent fuel produced at Indian Point in three decades is still here -- and not at Yucca Mountain, the federal government's burial spot near Las Vegas, where it was supposed to be shipped beginning six years ago.