Enhanced analysis methods to derive the spatial distribution of I deposition on the ground by airborne surveys at an early stage after the Fukushima Daiichi Nuclear Power Plant accident

Torii, Tatsuo  ; Sugita, Takeshi*; Okada, C. E.*; Reed, M. S.*; Blumenthal, D. J.*

In March 2011 the second largest accidental release of radioactivity in history occurred at the Fukushima Daiichi Nuclear Power Plant following a magnitude 9.0 earthquake and subsequent tsunami. Teams from the US Department of Energy National Nuclear Security Administration Office of Emergency Response performed aerial surveys to provide initial maps of the dispersal of radioactive material in Japan. The initial results from the surveys did not report the concentration of iodine-131 (I). This work reports on analyses performed on the initial survey data by a joint Japan-US collaboration to determine I ground concentration. As a result of this analysis, although the analytical results show a high concentration of I northwest of the NPP, consistent with the previously reported radioactive cesium (Cs and Cs) deposition, the I deposition shows a significant concentration south of the plant which is not represented in the radioactive cesium map.