Fig. 1

One-hour resolution radiation dose rate data at 12 locations within 100 km from the Fukushima Dai-ichi Nuclear Power Plant (FNPP). The data is presented using a logarithmic scale over two and half months after the Fukushima nuclear accident (in UT) from 16 March although the accident started already on 11 March with the largest release on 14 March. Directions and distances from the FNPP (S: south, W: west, N: north) are given in the legend. The first three letters of each location are used as an abbreviation in the plot. The drop in values at Takahagi on 19 April 9 UT is due to a change of the measurement site. Measurements are made at 1∼1.5 m height from the ground at all 12 locations using a NaI Scintillator with a supplement Ionization Chamber for > 10 µGy/h cases.