Measurement Example of Radiation Dose Rate in Private Premises Contaminated by the Fukushima Nuclear Power Plant Accident

Abstract

Four of premises decontamination. for attenuation by consid-eration of the radioactive half-lives of 134 Cs and 137 Cs to compensate the time gap between the sur-veyed dates. Measuring points were categorized by an index of a pair of indoor positions and the height from the fl oor as well as outdoor positions and the height from the ground. The observed differ-ences among the dose rates under this categorization, for example, the rate on the second fl oor is lower than that of the ceiling of the fi rst fl oor, qualitatively agree with the reported results of simulations, suggesting that some assumptions used by the simulations coincide reasonably well with actual condi-tions. The observed ratio of the doses inside and outside of wooden houses also essentially agrees with the reported ratio measured by different methods in different cities. The ratio has been con fi rmed to decrease with increasing open air dose rate when the open air dose rate is less than 0.5 μ Sv / h.