Fukushima radioactivity detected for the first time along B.C. coastline; levels harmless
Monday, April 13, 2015, 3:23 PM - A water sample collected along the west side of Vancouver Island has returned the first definitive detection of radioactive cesium from the Fukushima Daiichi power plant along the British Columbia coast.
Ever since the devastating earthquake that struck the Japan coastline in March 2011, and the resulting damage to the Fukushima Daiichi nuclear power plant, radioactive elements from the plant - specifically cesium-137 and cesium-134 - have been carried across the Pacific Ocean by currents. Scientists have tracked the progress of this migration, using both computer modelling and water sampling, and one of the latest results - drawn from the water in February in Ucluelet, British Columbia - has revealed very low levels of cesium-134.
Radioactive cesium (at least isotopes -137 and -134) occurs in ocean water mostly a result of nuclear weapon tests during the Cold War. However of the two, cesium-134 has a very short half-life of only a little over 2 years. This means that just two years after it is released into the environment, only half of the cesium-134 is still in that radioactive form. Two years after that, and only a quarter of the original cesium-134 is still in that form, and so on. The rest has undergone 'beta decay', where one of the neutrons in its atomic nucleus converts into a proton, resulting in an atom of Barium-134 and the release of a gamma ray.
With this rapid decay of cesium-134, it's doubtful that any would be left over from the weapon testing in the Pacific. By comparison, cesium-137 has a half-life of 30 years, so there would be far more of that isotope still around in the water. So cesium-134 has been what scientists, like those at the Woods Hole Oceanographic Institution (WHOI), have been searching for to determine where the radioactive elements from Fukushima have reached.
Previous tests have yielded detections along the northern coast of California, but nothing had been detected along the British Columbia coastline until now.
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Although this detection of cesium-134 gives scientists valuable information on how quickly ocean currents are carrying these elements, the radioactivity from both of these isotopes is far below international safety standards for exposure to radiation.
"Radioactivity can be dangerous, and we should be carefully monitoring the oceans after what is certainly the largest accidental release of radioactive contaminants to the oceans in history," said Ken Buesseler, a WHOI marine chemist, said in a press release on Monday. "However, the levels we detected in Ucluelet are extremely low."
According to the WHOI press release:
The Ucluelet sample contained 1.4 Becquerels per cubic meter (Bq/m3) (the number of decay events per second per 260 gallons of water) of cesium-134, a telltale sign of having come from Fukushima, and 5.8 Bq/m3 of cesium-137. These levels are comparable to those measured 100 miles off the coast of Northern California last summer. If someone were to swim for 6 hours a day every day of the year in water that contained levels of cesium twice as high as the Ucluelet sample, the radiation dose they would receive would still be more than one thousand times less than that of a single dental x-ray.
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Where will it be detected next?
As the map above indicates, the currents along the British Columbia and US coastlines splits roughly near the border, with warmer waters flowing south along California and cooler waters flowing north along British Columbia and up to Alaska. This means that cesium-134 flowing along with that current will spread in both directions, and will likely be detected at sites up and down the coast in the future.
"We expect more of the sites will show detectable levels of cesium-134 in coming months, but ocean currents and exchange between offshore and coastal waters is quite complex," Buesseler said in the press release, "Predicting the spread of radiation becomes more complex the closer it gets to the coast and we need the public’s help to continue this sampling network."
For those living along the coast, there's no need to fear the levels of radiation that are being detected, but the public not only has access to the data being collected, but they can also help the scientists track the spread of the radioactive elements.
The Integrated Fukushima Ocean Radionuclide Monitoring (InFORM) Network, being coordinated by Jay Cullen at the University of Victoria, has many volunteers gathering water samples, and there is plenty of information on the InFORM website about the progress and results of the network.
In addition, Buesseler has organized a similar network on the U.S. side of the border, which collects its information and results at OurRadiactiveOcean.org.
Where will this radioactivity spread afterward? The Earth's oceans are so interconnected that scientists refer to the overall circulation as the 'Global Conveyor Belt'. This flow travels on a circuitous route around the globe, and a specific parcel of water from the northeast Pacific Ocean can travel down past California, across to the Indian Ocean, around the tip of Africa, up through the south Atlantic to the Gulf of Mexico, and into the North Atlantic before turning around and reversing the trip. However, seeing as a complete circuit of the Global Conveyor Belt takes on the order of 1,000 years, it would be several hundred years before Fukushima radiation could make it to the east coast of North America. That is more than enough time for the cesium-134 to have decayed away and nearly all of the cesium-137 to have done the same.