The half-life of U-235 (as used in nuclear reactors) is 700 million years. Naturally occuring uranium is mostly U-238 which has a half-life of 4.5 billion years. It gives off so little radiation that at the Science Centre near hear they have a display on density with large bricks of aluminum, lead, and uranium that visitors can pick up to feel the differences in weights. Pu-239 (the isotope of plutonium used in atomic bombs, and one of the more stable waste products of nuclear power production) has a half life of 24,000 years. It's 200,000 times more radioactive than naturally occuring uranium. Pu-241 is another waste product and it has a half life of 14 years. Jason From: "James Newton, Host" Sent: Wednesday, August 25, 2004 4:52 PM > Says who? Why? -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics