February 25th, 2014 by Sandy Dechert
Bad news from the annual American Geophysical Union’s Ocean Sciences Meeting in Honolulu. Researchers there announced today that radioactive isotopes from the Fukushima nuclear disaster, when three reactors melted down after the March 11, 2011, Tohoku earthquake and subsequent mega-tsunami, have finally reached the West Coast.
John Smith, a research scientist at Canada’s Bedford Institute of Oceanography in Dartmouth, Nova Scotia, told the AGU meeting that since 2011 he and colleagues had measured a radioactive plume from nuclear complex at ocean monitoring stations west of Vancouver. Fukushima’s radiation reached Canada before the US on the powerful Kuroshio Current. It’s predicted to flow south and then circle back to Hawaii.
There is some good news, though. The two radioactive cesium isotopes found in Canada (cesium-134 and cesium-137) are far below the nation’s safety limit, at least for now. In Scientific American, Becky Oskin points out:
“The U.S. safety limit for cesium levels in drinking water is about 28 Becquerels, the number of radioactive decay events per second, per gallon (or 7,400 Becquerels per cubic meter). For comparison, uncontaminated seawater contains only a few Becquerels per cubic meter of cesium.”
The Fukushima cesium radiation is expected to peak in about two years. The nuclear accident also released other radioactive isotopes, such as iodine-131.
Bahar Gholipour of LiveScience elaborates on the significance of the discovery:
“Some of the radioactive elements released in the accident, such as cesium-134, have a short half-life; they decay to half their original amount within two years. However, cesium-137, which has a half-life of more than 30 years, continues to be a source of radiation.”
“The only cesium-134 in the North Pacific is there from Fukushima,” Smith said. Cesium-137, which remains in the environment for decades, is still present in the Pacific from nuclear weapons tests and nuclear power plant discharges.
Ken Buesseler, a senior scientist at the Woods Hole Oceanographic Institute in Woods Hole, Mass., says that tests on eight U.S. beaches indicate that the Fukushima radiation has not yet reached Washington, California, or Hawaii, although leftover cesium-137 levels at U.S. beaches were 1.3 to 1.7 Becquerels per cubic meter. His team is now awaiting results from a February 2014 sampling trip.
Two competing models have predicted that Fukushima radiation will begin to arrive on the West Coast about now. Both expect it to peak in 2016. They differ by a factor of 10 in predicted peak concentration of cesium, but both estimates are well below the highest level in the Baltic Sea after Chernobyl.
Convinced that even low levels of contamination should be monitored, Buessler launched a website called “How Radioactive is Our Ocean?” in January. The site allows scientists and officials to propose and fund new sampling locations along the West Coast. The public is invited to donate for analysis of existing water samples.
In a similar effort we reported last month, Steven L. Manley of Cal State at Long Beach and Lawrence Berkeley National Laboratory’s Kai Vetter have set up monitoring off the state’s coast throughout 2013 to determine the extent of radioactive contamination in the state’s extensive nearshore kelp forest.
Meanwhile, back in Japan, radioactive water continues to escape from the Fukushima site. The Tokyo Electric Power Company had denied leakage until last August, when the evidence became undeniable. TEPCO reported a new leak just last week.
It’s also ironic that this news comes at a time when residents of the Fukushima area are being allowed to return to their homes, TEPCO has just stopped the fuel removal operation at Reactor Unit 4, and Japanese politics is heating up about whether or not to recommit to nuclear power.
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