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III Radiation Survey of the Environment

Environmental Radiation Status In and Around Tokyo Immediately After the TEPCO Fukushima Dai-ichi Nuclear Power Plant Disaster

Takeshi Iimoto, Hirofumi Fujii, Seiichi Someya, Sadao Iiizumi, Takao Ebisawa, Seiichi Hirose, Etsuko Furuta, Keiji Kusama, Norio Nogawa, Hiroshi Mitani, Masao Kamiko, Natsumaro Kutsuna, Yasuhiro Watanabe, and Takahiko Suzuki

Abstract An example of environmental radiation status in and around Tokyo immediately after the TEPCO Fukushima Dai-ichi Nuclear Power Plant (NPP) disaster is introduced. The east part of the Metropolis of Tokyo and northwest of Chiba Prefecture are located about 200–250 km south from the NPP. The local governments in the area have officially surveyed the environmental radiation status after the disaster in response to numerous requests from their citizens. The radiation surveillance by local governments has been conducted and technically guided by the radiation protection specialists. The two main goals of the surveillance are (1) to measure the ambient radiation dose (microsieverts per hour) at all the schoolyards, public parks, and representative measuring points selected by the local government, and (2) to measure the specific radioactivity (becquerels per kilogram) of drinking water and local food items. In parallel with these movements, radiation experts in the University of Tokyo also organized a special correspondence team to survey the environmental radiation status immediately after the nuclear disaster. These activities and related data are introduced in this chapter.

Keywords Ambient radiation dose • Chiba • Specific radioactivity • Tokyo

Introduction

Kashiwa City and Nagareyama City are located in the northwest part of Chiba Prefecture in the metropolitan area of Tokyo, Japan. These cities are located roughly 200 km southward from the TEPCO Fukushima Dai-ichi Nuclear Power Plant (NPP). Bunkyo ward in Tokyo is at a distance of 220 km south of the NPP. The office location and other detailed information of these three cities are listed in Table 5.1.

These local governments have officially surveyed the environmental radiation status immediately after the disaster in response to requests from their citizens. The radiation surveillance in this area has been conducted and technically guided by radiation protection specialists.

The University of Tokyo is also located mainly in the metropolitan area of Tokyo, Japan. This university owns three main campuses: the Hongo campus and the Komaba campus are located in the middle-eastern part of the Metropolis of Tokyo, and the Kashiwa campus is located in the northwestern part of Chiba Prefecture. The distance between the NPP and the three campuses ranges from about 200 to 250 km. Immediately after the nuclear disaster, the university organized a special corresponding team to survey the environmental radiation status in the site of the university. The team consists of about 20 members and includes mostly radiation protection specialists or technical experts of the university specialized in radiation measurement. This project is not research oriented; rather, the purpose is to provide, in the absence of related information, the actual data on environmental radiation immediately after the accident. This information had been continuously provided both to the university community members and to the public through a website.

Table 5.1 Location, area, and population of the cities as of April 1, 2012

City name

Prefecture

Office location (-°-′-″)

Area (km2)

Population

Kashiwa City

Chiba

35-52-05N

114.9

404,252

139-58-35E

Nagareyama City

Chiba

35-51-31N

35.28

166,493

139-54-9E

Bunkyo ward

Tokyo

35-42-29N

11.31

201,079

139-45-9E

This chapter provides the background status and technical information on the related activities together with the estimated environmental radiation data at that time.

 
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