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Old 08-20-2013, 01:11 PM   #15
alkemical
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http://news.nationalgeographic.com/n...ve-water-leak/

Quote:
Q: How far is the radiation spreading, and how fast does it travel?

The initial gigantic deluge of contaminated water dispersed through the immediate ***ushima coastal area very quickly, according to a 2012 report by the American Nuclear Society. But it takes years for the contamination to spread over a wider area. A mathematical model developed by Changsheng Chen of the University of Massachusetts at Dartmouth and Robert Beardsley of the Woods Hole Oceanographic Institute found that radioactive particles disperse through the ocean differently at different depths. The scientists estimated that in some cases, contaminated seawater could reach the western coast of the United States in as little as five years. Buesseler thinks the process occurs a bit more rapidly, and estimates it might take three years for contamination to reach the U.S. coastline.

Q: What are the potential risks to humans, and who might be affected by the contamination?

This is a murky question, because it’s not that easy to determine whether health problems that may not show up for decades are caused by exposure to radioactive contamination. A report released in February by the World Health Organization, which was based upon estimates of radiation exposure in the immediate wake of the accident, concluded that it probably would cause "somewhat elevated" lifetime cancer rates among the local population. But figuring out the effect of years of exposure to lower levels of radioactive contamination leaking into the ocean is an even more complicated matter.


Minoru Takata, director of the Radiation Biology Center at Kyoto University, told the Wall Street Journal that the radioactive water doesn’t pose an immediate health threat unless a person goes near the damaged reactors. But over the longer term, he’s concerned that the leakage could cause higher rates of cancer in Japan.

Marine scientist Buesseler believes that the leaks pose little threat to Americans, however. Radioactive contamination, he says, quickly is reduced "by many orders of magnitude" after it moves just a few miles from the original source, so that by the time it would reach the U.S. coast, the levels would be extremely low. (See related, “Rare Video: Japan Tsunami.”)

Q: Will seafood be contaminated by the leaks?

As Buesseler’s research has shown, tests of local fish in the ***ushima area still show high enough levels of radiation that the Japanese government won’t allow them to be caught and sold for human consumption—a restriction that is costing Japanese fishermen billions of dollars a year in lost income. (But while flounder, sea bass, and other fish remained banned for radiation risk, in 2012 the Japanese government did begin allowing sales of octopus and whelk, a type of marine snail, after tests showed no detectable amount of cesium contamination.)

Buesseler thinks the risk is mostly confined to local fish that dwell mostly at the sea bottom, where radioactive material settles. He says bigger fish that range over long distances in the ocean quickly lose whatever cesium contamination they’ve picked up. However, the higher concentration of strontium-90 that is now in the outflow poses a trickier problem, because it is a bone-seeking isotope. "Cesium is like salt—it goes in and out of your body quickly," he explains. "Strontium gets into your bones." While he’s still not too concerned that fish caught off the U.S. coast will be affected, "strontium changes the equation for Japanese fisheries, as to when their fish will be safe to eat." (See related blog, “Safety Question on ***ushima Anniversary: Should Plants of the Same Design Have Filtered Vents?”)

This story is part of a special series that explores energy issues. For more, visit The Great Energy Challenge.
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