With the possibility that terrorists might someday detonate a nuclear bomb on American soil, the federal government is studying ways to figure out quickly who exploded a bomb and where the nuclear material came from.
The effort began 5 years ago but is only now coming to light. Government weapon laboratories are hiring experts, calling in "old-timers", pulling up old files and holding drills to get them ready ASAP.
The project leader for nuclear identification research said, "We're putting all these things together with the hope that they'll never have to be used". A similar program was discontinued after the Cold war when the nuclear threat was thought over. Source