第4章患者救済に奔走した活動記録〈論文・研究発表〉FUKUSHIMA いのちの最前線495RADIATION MEASUREMENTS AT THE CAMPUS OF FUKUSHIMA MEDICAL UNIVERSITYFukushima J. Med. Sci.,Vol. 57, № 2, 2011THROUGH 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)INTRODUCTION Fukushima Medical university (later often referred to as 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 小林恒夫Corresponding 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 the 11th of March, 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 1 nuclear accidents, earthquake and tsunami, radiation surveillance, natural radiation