A small amount of radioactive, weapons-grade plutonium about the size of a U.S. quarter is missing from an Idaho university that was using it for research, leading federal officials on Friday to propose an $8,500 fine. The U.S. Nuclear Regulatory Commission said Idaho State University can't account for about a 30th of an ounce (1 gram) of the material that's used in nuclear reactors and to make nuclear bombs. The amount is too small to make a nuclear bomb, agency spokesman Victor Dricks said, but could be used to make a dirty bomb to spread radioactive contamination. "The NRC has...