Saturday, 29 December 2012

Contamination from Fukushima


Video: Distribution of Cesium-137 contamination in the Pacific Ocean from Fukushima, modeled to the year 2021




27 December, 2012


[Machine translation] 

 Kiel, 9 July 2012 (GEOMAR) – The nuclear disaster in the Japanese Fukushima device back into oblivion. Large quantities of radioactive substances released it spread but still in the Pacific. Scientists of GEOMAR | Helmholtz Centre for Ocean Research Kiel have investigated the long-term spread with the help of a model study. Then, the strong mixing by oceanic Eddy ensures a rapid dilution of radioactive water. If the first runners reach the North American coast in about three years, the radioactivity should therefore already are below the values which today are found as a result of the Chernobyl disaster in the Baltic Sea.

Large quantities of radioactive material were released through the reactor catastrophe of Fukushima in March last year. A majority of concluded about the atmosphere, but also by direct discharge into the Pacific Ocean, including long-lasting isotopes such as the highly soluble in sea water cesium-137. With the help of detailed computer simulations of GEOMAR researchers | Helmholtz Centre for Ocean Research Kiel the long-term spread investigated. "In our models, we have placed great importance on a realistic representation of also fine details of the currents", said the head of the research team, Prof. Claus Böning, "because the substance spread is characterised not only by the mainstream, the Kuroshio, but significantly also through intensive and highly volatile vortex."

"According to our calculations the radioactive water should be been distributed through these strong turbulence already half North Pacific--almost the", explained diploma oceanographer Erik Behrens, first author in the international scientific journal "environmental research letters" published study. "In addition winter storms have mixed the water to depths of 500 meters." The resulting dilution ensures a rapid decrease of the cesium concentrations in the mathematical modeling.

The effect of the wide ocean mixing is particularly evident if one compares the timing of the radiation levels in the Pacific Ocean as simulated in the model with the conditions in the Baltic Sea. "In March and April 2011 in the Pacific Ocean flowed amount of radioactivity was at least three times as large as that which was registered in 1986 due to the Chernobyl disaster in the Baltic Sea," explains backer. "Nevertheless, the radiation levels simulated by us in the Pacific are already lower than the values today, 26 years after Chernobyl, in the Baltic Sea."

After the model simulation, first foothills of contaminated water should strip the Hawaiian Islands and two or three years later reached the North American coast in the autumn of 2013. Unlike floating to the surface debris, which are distributed by the wind, radioactive water is transported solely by the currents below the surface of the sea. The other concomitant dilution will slow down now but clearly since the oceanic Eddy in the Eastern Pacific are much weaker than in the Kuroshio region. Therefore, the radiation levels in the North Pacific well above those before the disaster are still over the years.

Very interested in Claus Böning would us his team to make direct comparison measurements. "Then we could see immediately whether we really are also the absolute sizes of the concentrations," says Prof. Böning. Such data for the Kiel researchers but are currently not available.

Original work:

Behrens, E., F.U. Schwarzkopf, J.F f. Lübbecke and C.W.. Böning, 2012: model simulations on the long-term dispersal of 137CS released into the Pacific Ocean off Fukushima.Environmental research letters, 7, http://dx.doi.org/10.1088/1748-9326/7/3/034004


Original work – in German - Fukushima - Wo bleibt das radioaktive Wasser?

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