我が国における原子力緊急事態と自然災害の避難関連パラメータの比較

Comparison of evacuation-related parameters between nuclear emergency and natural disaster from the experience in Japan

鯨岡 郁雄; 廣内 淳 ; 山口 文恵  ; 高原 省五 

Kujiraoka, Ikuo; Hirouchi, Jun; Yamaguchi, Fumie; Takahara, Shogo

Evacuation is one of the protective actions to avoid undue exposures to the public in a nuclear emergency. To achieve this action effectively, information on residents' behavior is essential. However, there is little data available because nuclear emergencies almost never happen. Therefore, if we try to update continuously information on those behaviors, the experiences from other than nuclear emergencies must be needed. Under this background, this study examined whether evacuation-related information from natural disasters in Japan could be applicable to a nuclear emergency. To explore evacuation-related information from natural disasters, a disaster impact database was constructed. Then, important disasters were selected from the database by using the methods proposed by the U.S. Nuclear Regulation Commission, and evacuation percentage, spontaneous evacuation percentage, and shadow evacuation percentage were evaluated from the important natural disasters. In addition, these evacuation related parameters for a nuclear emergency were also evaluated based on the experience of the Fukushima Daiichi Nuclear Power Plant accident and the results of social surveys which were conducted for Urgent Protective action planning zone (UPZ). For natural disasters, the evacuation percentage ranged 20% to 30%, spontaneous evacuation percentage ranged 30% to 80%, and shadow evacuation percentage was less than 1%. For a nuclear emergency, the evacuation percentage ranged 80% to 90%, spontaneous evacuation percentage ranged from a few percent to approximately 70%, and shadow evacuation percentage ranged 30% to 60%. The evacuation related parameters differed between natural disasters and a nuclear emergency, within the scope examined, there was insufficient evidence to justify their direct application to nuclear emergencies.