11.   Dirty thoughts to dirty bombs.

12.   Dirty bombs, nuclear weapons and reactors present different issues, of course.

13.   Even if that is so, it is impossible to tell how near al-Muhajir came to setting off a dirty bomb.

14.   Experts used to dismiss the possibility that terrorists might try to deploy dirty bombs, which would scatter radioactive material over a large area.

15.   Experts worry that terror groups might try to use that material to make even more dangerous dirty bombs.

16.   Hayden acknowledged that a terrorist could try to assemble a variety of radioactive materials into a dirty bomb.

17.   Gore is not unwittingly carrying a dirty bomb in his briefcase.

18.   He said the government must now work not only on preventing an attack but also on educating people on the facts about dirty bombs.

19.   If a dirty bomb is detonated, individual protection outside the immediate blast zone could be as simple as quickly showering and changing clothes, Miller said.

20.   In fact, a dirty bomb could appear to be simply a conventional explosion and no radiation release immediately noticed.