Development of deterministic approach to assess doses to the public from external exposures in the areas contaminated by the Fukushima Daiichi Nuclear Power Station Accident

Takahara, Shogo  ; Iijima, Masashi; Shimada, Kazumasa ; Kushida, Teruo; Shiratori, Yoshitake

In order to assess the doses to representative person using deterministic approach, we measured radiation dose rates and surveyed on behavioral patterns in the areas contaminated by the Fukushima Daiichi Nuclear Power Station Accident. Statistical analyzes were also performed to identify the characteristics of individual doses from external exposures, as well as radiation dose rates and behavioral patterns. Radiation dose rates measured in living areas distribute with lognormal form. Behavioral patterns of the populations were different corresponding to their occupation. Time spent outdoors of indoor workers were distributed in lognormal form and those of outdoor workers had the normal distribution. Multi-regression analyses were made to explore a significant relationship between individual doses and relevant contributors. These results indicated that the significant differences were given in individual doses due to the spatial differences of radiation dose rates as well as the interindividual differences of behavioral patterns. Based on the results of analyses of relevant contributors to the external exposures, deterministic dose assessment model was developed. The validity of this model was confirmed because the assessed values were higher than those measured.