Surveillance of Strontium-90 in Foods after the Fukushima Daiichi Nuclear Power Plant Accident

摘要

As a result of the Fukushima Daiichi nuclear power plant (NPP) accident, various radionuclides were released into the environment. In this study, we surveyed strontium-90 (~(90)Sr) concentrations in several foodstuffs. Strontium-90 is thought to be the third most important residual radionuclide in food collected after the Fukushima Daiichi, NPP accident after following cesium-137 (~(137)Cs) and cesium-134 (~(134)Cs). Results of ~(90)Sr analyses indicated that ~(90)Sr was detect in 25 of the 40 radioactive cesium (r-Cs) positive samples collected in areas around the Fukushima Daiichi NPP, ranging in distance from 50 to 250 km. R-Cs positive samples were defined as containing both ~(134)Cs and ~(137)Cs which are considered to be indicators of the after-effects of the Fukushima Daiichi NPP accident. We also detected ~(90)Sr in 8 of 13 r-Cs negative samples, in which ~(134)Cs was not detected. Strontium-90 concentrations in the r-Cs positive samples did not significantly exceed the ~(90)Sr concentrations in r-Cs negative samples or the ~(90)Sr concentration ranges in comparable food groups found in previous surveys before the Fukushima Daiichi NPP accident. Thus, ~(90)Sr concentrations in r-Cs positive samples were indistinguishable from the background ~(90)Sr concentrations arising from global fallout prior to the Fukushima accident, suggesting that no marked increase of ~(90)Sr concentrations has occurred in r-Cs positive samples as a result of the Fukushima Daiichi NPP accident.