Japan Chemical Analysis Center, 295-3 Sanno-cho, Inage-ku, Chiba-shi, Chiba 263-0002, Japan.
Health Phys. 2012 Apr;102(4):437-42. doi: 10.1097/HP.0b013e31823bc2d3.
Damage to the Fukushima nuclear power plant caused by the 11 March 2011 earthquake and tsunami off the northeast coast of Japan resulted in the release into the environment of radioactive material. Airborne radioactive material was detected in metropolitan areas near Tokyo, and increases in radiation dose rate were observed at many locations. In this study, repeated measurements with the in situ Ge system were performed in Chiba City, which is about 220 km south of Fukushima. Increases in radiation dose rate were recorded on 15, 16, and 21 March, with a maximum of 0.5 μGy h(-1). This level is clearly higher than natural background in Japan. Airborne (99)Mo, (99m)Tc, (129m)Te, (129)Te, (132)Te, (131)I, (132)I, (133)I, (133)Xe,(133m)Xe, (135)Xe, (134)Cs, (136)Cs, (137)Cs, and (140)La were detected. Environmental radioactive contamination in the metropolitan area occurred mainly on 21 March by rainfall. The initial rates of decrease in radiation dose rate generally reflected radiological decay according to their physical (radiological) half-lives. However, the in situ half-lives of the long-lived radionuclides such as (134)Cs and (137)Cs reflected environmental dispersal rather than radiological decay.
2011 年 3 月 11 日日本东北部沿海地震和海啸对福岛核电站造成的破坏导致放射性物质释放到环境中。在东京附近的大都市区检测到了空气传播的放射性物质，许多地方的辐射剂量率都有所增加。在这项研究中，在距离福岛约 220 公里的千叶市使用现场 Ge 系统进行了重复测量。3 月 15 日、16 日和 21 日记录到辐射剂量率增加，最大值为 0.5 μGy h(-1)。这一水平明显高于日本的自然背景。检测到空气中的 (99)Mo、(99m)Tc、(129m)Te、(129)Te、(132)Te、(131)I、(132)I、(133)I、(133)Xe、(133m)Xe、(135)Xe、(134)Cs、(136)Cs、(137)Cs 和 (140)La。大都市地区的环境放射性污染主要发生在 3 月 21 日的降雨中。辐射剂量率的初始下降速度通常反映了根据其物理（放射性）半衰期的放射性衰减。然而，长寿命放射性核素如 (134)Cs 和 (137)Cs 的现场半衰期反映了环境的扩散，而不是放射性衰减。
