@misc{oai:repo.qst.go.jp:00071009,
 author = {Watanabe, Yoshito and Fuma, Shoichi and Kubota, Yoshihisa and Yoshida, Satoshi and et.al and 渡辺 嘉人 and 府馬 正一 and 久保田 善久 and 吉田 聡},
 month = {Dec},
 note = {During the Fukushima nuclear accident in March 2011, radionuclides released to the atmosphere contaminated the surrounding environment. The largest radioactive plumes from the power plant flew west to north-westward, where forest land is widely distributed. In the past nuclear accident in Chernobyl in 1986, radioactive plumes have contaminated the surrounding forest, which have caused massive radiation damage in forest trees. The damages became obvious by the first summer after the accident in the highly contaminated forest area, where have been called the Red Forest from the color of the dead tree stands. In this study, a preliminary survey was made in forest areas within the 20 km exclusion zone around the Fukushima Daiichi Nuclear Power Plant for the distribution of radionuclides and the radiation effects on trees during the first year after the accident. The collection of the tree samples was carried out for three native coniferous species, Japanese red pine, Japanese cedar and Japanese cypress at 3 sampling locations differing in distance and direction from the nuclear power plant during the period from November 2011 to March 2012 as part of a project by the Ministry of the Environment, Japan. The external gamma dose rate in each sampling location was measured at 1 m above the ground with NaI scintillation or ionization chamber type survey meter. Radioactive contamination in the samples was first analyzed nondestructively with an imaging plate. The separated and homogenized samples were further analyzed for radionuclides using a Ge semiconductor detector. One of the sampling locations situated in the highest contaminated area in approximately 3 km in the northwest direction from the power plant. Even in the area, no externally visible symptoms of radiation damages including yellowing, malformation and early withering of leaves were observed in trees, indicating massive radiation damage like the Red Forest did not occur in the forest after the Fukushima accident. The external gamma dose rate exceeded 50 µSv/h in the highest contaminated sampling location, and varied widely among the sampling locations. The levels of radionuclides, 134Cs and 137Cs, in the tree changed depending on the contamination level of the forest, approximately on external radiation dose rate. The radionuclides not only adhered to the surface of the old leaves, but also distributed in the new leaves, flowers, cones and seeds that developed during the spring to autumn after the accident. This indicates translocation of the radionuclides to newly developing tissues, which should have caused an additional internal exposure of meristematic and reproductive tissues. The exposed dose rate of trees in the highest contaminated forest was likely to be higher than a criteria dose rate of 4-40 µGy/h selected for pine trees by ICRP (2009), which raises the necessity of more detailed analyses of cytogenetic and reproductive damages in forest trees in the area., International Symposium on Environmental monitoring and dose estimation of residents after accident of TEPCO's Fukushima Daiichi Nuclear Power Stations},
 title = {Effects of radionuclide contamination on forest trees in the exclusion zone around the Fukushima Daiichi Nuclear Power Plant},
 year = {2012}
}