In this Sept. 19, 1973 photo provided by the U.S. Department of Energy, a worker holds a plutonium “button” inside a chamber using protective gloves at the Rocky Flats nuclear weapons plant northwest of Denver. The U.S. Energy Department manufactured plutonium triggers for nuclear warheads at Rocky Flats. It had a long history of leaks, fires and environmental violations. CREDIT: U.S. DEPT. OF ENERGY via AP

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