Japan Radiation Release, Ocean Currents

April 06, 2011; 3:58 AM
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The operator of the crisis-hit Fukushima Daiichi nuclear power plant has released 11,500 tons of radioactive water into the sea, as had been announced on Monday.

The release of water took place Monday and Tuesday at the site, located on the northeast coast of Honshu, the main island of Japan.

The release coincided with statements from the plant's operator saying that radioactive iodine levels were as high as 7.5 million times the legal limit, even before the controlled release, in samples taken from the sea next to the water intake for one of the reactors.

Along with the radioactive iodine-131 isotope, radioactive cesium-134 and cesium-137 were also present in concentrations more than 1 million times the allowable limit.

The operator has reportedly taken steps to control the spread of radiation from the intentionally released water, and from the ongoing leaks. However, the source and path of the leaks are not fully understood.

Any radioactive water escaping confinement will be subjected to the pull of ocean currents. Off northeastern Honshu, the foremost current is the southward-flowing Oyashio. This current normally drifts southward to nearly Choshi, on Cape Inubo. Choshi is located about 60 miles east of Tokyo.

Off Cape Inubo, flow of the Oyashio gets shunted eastward by the more powerful Kuroshio, a major current flowing eastward south of Japan, heading for the open Pacific Ocean.

Whatever the consequences stemming from the dumping of the radioactive water, they should be greatest near and immediately down-flow of the nuclear plant. The overwhelming volume of the ocean would increasingly dilute contaminated water with distance from the point of release, eventually lowering radiation levels to those not far from the natural background.

On Monday, it was reported that fish caught off Ibaraki Prefecture, south of the Fukushima site, had an abnormally high concentration of iodine-131.


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