Reuters: Nuclear and radioactive materials are still going missing and the information the United Nations atomic agency receives about such incidents may be the tip of the iceberg, said a senior U.N. official. Any loss or theft of highly enriched uranium, plutonium or different types of radioactive sources is potentially serious as al Qaeda-style militants could try to use them to make a crude nuclear device or a so-called dirty bomb, experts say. Khammar Mrabit, a director of the U.N.'s International Atomic...