title: Early in situ measurement of radioactive fallout in Fukushima city due to Fukushima Daiichi nuclear accident.
abstract: Using a high-purity germanium detector, both indoor and outdoor radionuclides that had deposited 1.5 d after the radioactive fallout events in the city of Fukushima were experimentally measured. Eleven artificial ((131)I, (132)I, (134)Cs, (136)Cs, (137)Cs, (129)Te, (129m)Te, (131m)Te, (132)Te, (140)La and (99m)Tc) and 5 natural radionuclides were identified. Total air kerma rates were mainly due to (132)I, (134)Cs and (136)Cs from 4 to 6 µGy/h at a 7.5-cm height from the ground. Radioactive contamination on the ground was contributed by (132)I and (132)Te, from 330 to 420 Bq/cm(2). In a worst-case scenario, the maximum skin dose rates were estimated to be from 520 to 670 µGy/h. Effective dose rates were evaluated to be 10 to 15 µSv/h and reached 17.9 µSv/h at 4 a.m. on 16 March. In the effective dose rates, (132)I, (134)Cs and (132)Te were the main contributors. Our measurements are useful for estimating dose levels in the public in the city of Fukushima during the days after radioactive fallout contamination.
authors.affiliation: National Institute of Radiological Sciences, Chiba 263-8555, Japan. m_takada@nirs.go.jp
authors.forename: Masashi
authors.initials: M
authors.lastname: Takada
authors.forename: Toshikazu
authors.initials: T
authors.lastname: Suzuki
mesh_terms: D000396:Air Pollutants, Radioactive / Q000032:analysis*; D001417:Background Radiation; D002947:Cities; D003198:Computer Simulation; D062406:Fukushima Nuclear Accident; D006801:Humans; D007564:Japan; D009010:Monte Carlo Method; D011834:Radiation Monitoring; D011847:Radioactive Fallout / Q000032:analysis*; D018788:Radioactive Hazard Release; D012867:Skin / Q000528:radiation effects*
chemical_list: D000396:Air Pollutants, Radioactive; D011847:Radioactive Fallout