August 31, 2011 Corrections of the Results of Airborne Monitoring Surveys by MEXT and Ibaraki Prefecture The results of airborne monitoring survey by MEXT and Ibaraki prefecture released on August 30 contained some errors, and they are corrected as follows. 1. Corrections of the measurement results In order to increase the accuracy of the readings of airborne monitoring, MEXT calculated the proportional relationship between deposition amounts of radioactive substances on the ground surface and air dose rates (hereinafter referred to as the conversion factor ), based on the results of nuclide analysis of soil samples collected at around 2,200 locations during the period from June to July. Using the obtained conversion factor, MEXT revised the results of the third airborne monitoring survey and following surveys of Miyagi prefecture and Tochigi prefecture (already released on August 30). Although this new conversion factor should be used for calculating deposition amounts of radioactive cesium also with regard to the airborne monitoring survey by MEXT and Ibaraki prefecture, the old conversion factor was used in calculation except for on data for the southern part of Ibaraki prefecture. As a result, for some part of the prefecture, the obtained deposition amounts of radioactive cesium were larger than the actual values. Therefore, the readings of airborne monitoring surveys by MEXT and Ibaraki prefecture are corrected by making the calculation anew with the correct conversion factor (Attachments 1 to 6). (There are no changes in references 1 and 2, which show the measurement results of air dose rates on a map.) 2. Measures to be taken in the future The analysis of the results of airborne monitoring surveys has so far been conducted by the Nuclear Safety Technology Center. From now on, the Japan Atomic Energy Agency, which jointly carries out airborne monitoring surveys, will cross-check the analysis results in addition to the Nuclear Safety Technology Center, so as to verify the validity of the measurement results.
Results of the Airborne Monitoring Survey by MEXT and Ibaraki Prefecture 文部科学省及び茨城県による航空機モニタリングの結果 Attachment 別紙１1 (Total accumulation of Cs-134 and Cs-137 (Bq/m2) on the ground surface in Ibaraki prefecture) 茨城県内の地表面へのセシウム134 137のの合計 Legend Total accumulation of Cs-134 and Cs-137 (Bq/m2) [Converted to values as of August 2] Areas without measurement results
Results of the Airborne Monitoring Survey by MEXT and Ibaraki Prefecture 文部科学省及び茨城県による航空機モニタリングの結果 (Accumulation of Cs-134 on the ground surface in Ibaraki prefecture) 茨城県内の地表面へのセシウム134の Legend Accumulation of Cs-134 (Bq/m2) [Converted to values as of August 2] Areas without measurement results Attachment 2 別紙２
Results of the Airborne Monitoring Survey by MEXT and Ibaraki 文部科学省及び茨城県による航空機モニタリングの結果 Prefecture 茨城県内の地表面へのセシウム137の (Accumulation of Cs-137 on the ground surface in Ibaraki prefecture) Legend Accumulation of Cs-137 (Bq/m2) [Converted to values as of August 2] Areas without measurement results Attachment 別紙３ 3
文部科学省及び茨城県による航空機モニタリングの結果 ( 文部科学省がこれまでに測定してきた範囲及び茨城県内の地表面へのセシウム 134 137 のの合計 ) 別紙 4
文部科学省及び茨城県による航空機モニタリングの結果 ( 文部科学省がこれまでに測定してきた範囲及び茨城県内の地表面へのセシウム 134 の ) 別紙 5
文部科学省及び茨城県による航空機モニタリングの結果 ( 文部科学省がこれまでに測定してきた範囲及び茨城県内の地表面へのセシウム 137 の ) 別紙 6
Results of the Airborne Monitoring Survey by MEXT 文部科学省及び茨城県による航空機モニタリングの結果 茨城県内の地表面から１m高さの空間線量率 (Air dose rates at the height of 1m above the ground surface in Ibaraki prefecture) Legend Air dose rates at the height of 1m above the ground surface (μsv/hr) [Converted to values as of August 2] Areas without measurement results (Reference 1) 参考１
Results of the Airborne Monitoring Survey by MEXT 文部科学省による航空機モニタリングの結果 (Reference 2) 参考２ (Air dose rates at the height of 1m above the ground surface in Ibaraki prefecture and参考１ 文部科学省がこれまでに測定してきた範囲及び茨城県内 other areas where MEXT has conducted airborne monitoring surveys) における地表面から1m高さの空間線量率 Legend Air dose rates at the height of 1m above the ground surface (μsv/hr) [Converted to values as of August 2] Areas without measurement results