Approximately 60,000 people lived within the 20- to 30-km shelter-in-place zone (UNSCEAR, 2013b). On March 25, these residents were advised by the government to begin voluntary evacuations.
On April 22, 2011, the central government issued a new evacuation order to residents of Iitate, located outside the 20-km radius evacuation zone, where high radiation levels had been detected. Residents of that village were given 1 month to evacuate. The area was designated as a “Deliberate Evacuation Area.”
At this point onward the government switched from communicating evacuation orders on the basis of distance from the plant to using a threshold radiation dose of 20 mSv/yr as a basis for evacuation (Hasegawa, 2013). In June 2011, the government began to identify hotspots20 where radiation levels exceeded this 20-mSv/yr threshold. These hotspots were named “Specific Spots Recommended21 for Evacuation.” These hotspots were more than 20 km away from the Fukushima Daiichi plant and outside the Deliberate Evacuation Area (UNSCEAR, 2013b).
220.127.116.11 Potassium Iodide Distribution
In addition to evacuation and shelter-in-place orders, residents leaving the 20-km Restricted Zone were instructed to take potassium iodide (KI). This instruction was issued on March 16, four days after major releases of radioactive iodine (iodine-131) had begun and after about half of the iodine release had occurred (TEPCO, 2012b, Fig. 27). This was also 4 days after residents within the Restricted Zone were instructed to evacuate and a day after residents in the 20- to 30-km Evacuation Prepared Area were instructed to shelter in place. Upon issuing this instruction, KI was made available for distribution. The KI consisted of 1.51 million pills for 750,000 people and 6.1 kg powder for 120,000–180,000 people. However, the KI was likely not distributed because the evacuation had already been completed (Hamada et al., 2012).
On March 15, four towns close to the plant, Futaba, Tomioka, Iwaki,22 and Miharu, distributed in-stock KI pills to local residents without awaiting distribution instructions from the government. Futaba and Tomioka also instructed their residents to take the pills (Hayashi, 2011).
20 Hot spots are defined based on radioactive contamination levels. They are regions where contamination levels significantly exceed those in surrounding areas.
21 In other words, evacuations in these areas were not ordered.
22 Iwaki is located south of the area shown in Figure 6.1.