![]() ![]() When living organisms are exposed to radiation, the main effects are divided into early, intermediate and late as shown in Fig. Modulatory action can be explained by indirect effects.Īs for the biological effects of radiation, damage such as cancer is mainly considered. However, the difference is due to the type of radiation and physical and/or chemical conditions. ![]() Actually, both the direct and indirect effects of radiation cause biological damage. On the other hand, radiation can also directly inactivate substances in the body. This type of effect on living organisms is indirect. ( 4) These mayors can react withother substances in the body to initiate damage. On exposure to ionizing radiation, water, which is makes up more than 60% of the body, is ionized generating reactive oxygen species (ROS), such as hydrated electron (e aq −) and hydrogen radical ( The effect was particularly striking around Oshu City, where the dose rate increased by a factor of up to 10 between the first and the second surveys.Įarly Stages of Biological Effects of Radiation and Radiation Damage In the second and third surveys, the dose rate profile along the transect looked quite different. In the remaining part of the transect, however, the dose rates increased little, by a factor of about 1.5 to 2.5. In the first survey, dose rates along the expressway between Fukushima City and Osaki City were found to have increased markedly, from about 0.08 to up to 11 µGy h-1. 2 shows the temporal variation of dose rates in air before and after the start of the Fukushima NPP crisis. A shielding factor of 1.9 ± 0.04 was used.įig. Shielding by the car body was estimated by making measurements inside and outside of the car at 56 points. More than 100 measurements were obtained in each survey. Latitude and longitude at each measurement point were measured using a global positioning system (WPL-2000, Wintec Co., Ltd., Taiwan). The meter was calibrated with a 2'' × 2'' NaI (Tl) scintillation spectrometer (SPA-3, Eberline Co., New Mexico). A 1'' × 1'' NaI (Tl) scintillation survey meter (TCS-171, ALOKA Co., Japan) was used, and measurements were carried out every minute. Total distance on the expressway was about 1,256 km. The distance between the Fukushima NPP and measurement points ranged from 60 to 355 km, and the typical distance between measurements points was approximately 3 km. The measurements were conducted 3 times: on March 16, April 11 and April 25, 2011. ( 3) Car-borne surveys are commonly used for the rapid assessment of dose rates in emergency situations. At the same time, part of a wall in the operation area of Unit 4 is damaged.Ī fire breaks out in the Unit 4 reactor building.ĭose rates in air along an expressway passing northwest of the Fukushima Daiichi NPP were measured in a car-borne survey. Seawater injection into the Unit 2 pressure vessel begins.Īn explosion sound is heard at Unit 2 and it concluded to indicate an abnormality in the pressure suppression pool. The water level in the Unit 2 pressure vessel is found to be low, leading operators to conclude that the reactor cooling system is no longer functional. Water injection fails in the emergency core cooling systems of Unit 1 and 2.Ī hydrogen explosion damages the external structure of the Unit 3 reactor building. Water injection fails in the emergency core cooling system of Unit 3.Ī pressure relief valve is opened on the Unit 3 pressure vessel. Seawater injection to the Unit 1 pressure vessel begins. Water injection fails in the emergency core cooling systems of Units 1 and 2.Ī pressure relief valve is opened on the Unit 1 pressure vessel.Ī hydrogen explosion damages the structure of the Unit 1 reactor building. Ground acceleration triggers automatic shutdown of all three reactors in operation.Ī 14-meter tsunami triggered by the earthquake disables all AC power to Units 1, 2 and 3.įuel tanks for emergency diesel generators are carried off by the tsunami. ![]()
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