The information on the absorbed dose rate which is derived from natural radionuclides is needed to evaluate additional exposure dose. However, there is inadequate positional resolution and precision for such data around Fukushima Dai-ichi Nuclear Power Station (FDNPS). In this study, we created a map of the absorbed dose rate that is derived from natural radionuclides based on several airborne radiation monitoring data. The reliability and accuracy of the created map was verified by comparison with the many in-situ measurements on the ground. To evaluate the effectiveness of this study, the effective half-lives of the ambient dose rate at residential areas of Fukushima Prefecture were assessed by discriminating these absorbed dose rate of the natural background from the results of a periodic dose rate survey by local government. The results of the distribution of natural background absorbed dose rates are expected to contribute to the evaluation of the additional exposure dose after the FDNPS accident.

需要来自天然放射性核素的吸收剂量率信息，以评估其他暴露剂量。但是，福岛第一核电站（FDNPS）周围的此类数据的位置分辨率和精度不足。在这项研究中，我们基于几个机载辐射监测数据创建了一个从天然放射性核素得出的吸收剂量率的图。通过与许多原位比较，验证了所创建地图的可靠性和准确性在地面上测量。为了评估这项研究的有效性，通过从地方政府定期剂量率调查的结果中区分出自然背景的吸收剂量率，来评估福岛县居民区环境剂量率的有效半衰期。预期自然本底吸收剂量率的分布结果将有助于评估FDNPS事故后的其他暴露剂量。