VANCOUVER — Radioactivity from Japan’s crippled nuclear reactors has turned up off the British Columbia coast and the level will likely peak in waters off North America in the next year or two, according to a Canadian-led team that’s intercepted the nuclear plume.
The team’s seawater measurements reveal Fukushima radioactivity first showed up 1,500 kilometres west of British Columbia in June 2012, more than a year after the Japanese nuclear accident.
By June 2013, the “Fukushima signal” had spread onto the Canadian continental shelf off the B.C. coast, and by February 2014, it was detectable “throughout the upper 150 metres of the water column,” says the report, showing how the Pacific currents are carrying the radioactive plume slowly across the ocean. It says the Fukushima’s radioactive signal off the B.C. coast is now double the “background” radiation in the ocean from atmospheric nuclear bomb testing.
The scientists predict the Fukushima radioactivity off North America will continue to increase before peaking in 2015-16 at levels comparable to those seen in the 1980s as a result of nuclear testing. Then levels are expected to decline and, by 2021, should return to levels seen before that Fukushima accident — considered one of the most serious nuclear reactor accidents.
Smith’s work is part of an ocean monitoring program set up to trace the plume. Canadian Coast Guard ships travelling up to 1,500 kilometres off the B.C. coast and into the Beaufort Sea are collecting the seawater from depths of up to 1,000 metres and the scientists are testing it for the radioactive isotopes Cesium-137 and Cesium-134.
Cesium-137 is the bigger concern, as it lingers in the environment for decades. Cesium-134 decays much faster but is “an unequivocal fingerprint indicator of contamination from Fukushima,” the scientists say. This is because the Japanese reactor accident is the only large contributor of the compound into the Pacific Ocean other than fallout from nuclear bomb testing which peaked in the 1960s and has been dropping since.
Thus, the scientists predict the Cesium-137 levels off the North American coast will not return to the levels seen before the Fukushima accident until 2021.
Full article: Radioactivity from crippled Fukushima reactors turns up off B.C. coast (National Post)