NBC: Terror network seeks material to explode bomb in U.S. WASHINGTON, April 22 — A captured key strategist for the al-Qaida network told interrogators Monday that al-Qaida was working to obtain fissionable material for radiation bombs to be exploded in the United States, NBC News has learned. U.S. officials could not confirm the assertions of the strategist, Abu Zubaydah, but said they were taking him at his word. SOURCES TOLD NBC News that Zubaydah, believed to be one of the top lieutenants of Osama bin Laden, believed to be the mastermind of the Sept. 11 terrorist attacks in the United...