The United States today finds itself at greater risk of a radiological attack than at the height of the Cold War, according to government officials and independent experts. Concerns that had emerged way before the September 11 attacks have been exacerbated in recent months, as U.S. officials worry that terrorist groups may have access to radioactive materials that could be used to fabricate crude radiological dispersion devices and rudimentary nuclear bombs. But that is not the only reason for U.S. officials to fret. Of more significant concern is the wide availability of “orphaned” hardware and nuclear waste that conceivably could help a motivated terrorist or domestic separatist put together a weapon deadly enough to kill thousands of people.