FUKUSHIMA Lives on the Line

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230INTRODUCTIONFukushima Medical university (FMU) is located in the northeastern region of Japan (37°45'N, 140°28'E, 67.4 m above sea level), and is 57 km (35 miles) away from northwest of the Fukushima Daiichi nuclear power plant. The Tohoku region Pacific Coast earthquake occurred on 11 March, 2011, and Fukushima nuclear power plant accidents broke out subsequently.The present paper reports three groups of radiation measurement performed through the unexampled accidents. First, immediately after the earthquake, in order to investigate the levels of radiations outside and inside the campus, Associate Dean, School of Medicine, Professor Hiroyuki Yaginuma assembled a group of interested people from the faculty members of "Life Sciences and Social Medicine (basic medical sciences)" and "Human and Natural Sciences (liberal arts course)." Their hard-working efforts gave valuable information about radiation safety for many staff and patients in the hospital of FMU and the staff and students of FMU campus.Second, the present author had been measuring several natural radiations1) around his office from September in 2010. The natural radiations under the serial measurement were : gamma radiation in air with NaI scintillation counter, atmospheric radon with Lucas cell, and second cosmic rays with another NaI scintillation counter. Amongst the results of serial Radiation Measurements at the Campus of Fukushima Medical UniversityThrough the 2011 Off the Pacific Coast of Tohoku Earth­quake and Subsequent Nuclear Power Plant CrisisTsuneo KobayashiDepartment of Natural Sciences (Physics), School of Medicine, Fukushima Medical University, Fukushima, Japan(Received July 27, 2011, accepted August 31, 2011)Fukushima J. Med. Sci.,Vol. 57, № 2, 2011Tsuneo KobayashiCorresponding author : Tsuneo Kobayashi E-mail address : tkoba@fmu.ac.jphttp://www.jstage.jst.go.jp/browse/fms http://fmu.ac.jp/home/lib/F-igaku/Abstract : An earthquake, Tohoku region Pacific Coast earthquake, occurred on March 11, 2011, and subsequent Fukushima nuclear power plant accidents have been stirring natural radiation around the author's office in Fukushima Medical University (FMU). FMU is located in Fukushima City, and is 57 km (35 miles) away from northwest of the Fukushima Daiichi nuclear power plant. This paper presents three types of radiation survey undertaken through the unprecedented accidents at the campus and the hospital of FMU. First, a group of interested people immediately began radiation surveillance ; the group members were assembled from the faculty members of "Life Sciences and Social Medicine" and "Human and NaturaI Sciences." Second, the present author, regardless of the earthquake, had serially observed natural radiations such as gamma radiation in air with NaI scintillation counter, atmospheric radon with Lucas cell, and second cosmic rays with NaI scintillation. Gamma radiation indicated most drastic change, i.e., peak value (9.3 times usual level) appeared on March 16, and decreased to 1.7 times usual level after two months. A nonlinear least squares regression to this decreasing data gave short half-life of 3.6 days and long half-life of 181 days. These two apparent half-lives are attributed to two groups of radioisotopes, i.e., short half-life one of I-131 and long half-life ones of Cs-134, Cs-137 and Sr-90. Also, atmospheric radon concentration became high since a stop of ventilation, while second cosmic rays did not show any response. Third, late April, 2011, a team of radiation dosimetry under the direct control of Dean, School of Medicine, was established for the continuation of radiation survey in the campus and the hospital of Fukushima Medical University.Key words : Fukushima Daiichi nuclear accidents, earthquake and tsunami, radiation surveillance, natural radiation

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