Cows that consume feed, grass or water contaminated with radioactive iodine-131 can concentrate the element in their milk. Peter Elvidge/iStockphoto.com hide caption

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A view of the Three Mile Island power plant near Harrisburg, Pa., site of the worst nuclear accident in U.S. history. In 1979, a reactor at the plant experienced a partial meltdown, but radioactive material never escaped containment. Bradley Bower/AP Photo hide caption

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The facilities at the Fukushima Dai-ichi nuclear power plant were designed to withstand strong earthquakes and tsunamis, but not to the strength and size experienced on March 11. Air Photo Service/AP hide caption

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Mike Barlow has been installing geothermal systems for 20 years. But he says a 30 percent federal tax credit is increasing the popularity of the systems for families with modest houses. Elizabeth Shogren/NPR hide caption

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Tokyo Electric Power Co. Chairman Tsunehisa Katsumata (second from right) and other executives bow prior to a press conference at the company's headquarters in Tokyo on Wednesday. Kazuhiro Nogi/AFP/Getty Images hide caption

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Red #40, Blue #1, Yellow #6 - a rainbow of food dyes. Josh Roulston/Flickr hide caption

itoggle caption Josh Roulston/Flickr

In 1992, 28,800 rubber ducks were lost at sea. What happened to them is the subject of Donovan Hohn's book Moby-Duck. Jose Gil/iStockphoto.com hide caption

itoggle caption Jose Gil/iStockphoto.com