More details have emerged lately regarding assessments of measured levels of radioisotopes as well as the Japanese government’s strategy for a permanent evacuation zone. Soil measurements of radioactive cesium are distributed in patches throughout six municipalities: Okumamachi, Futabamachi, Namiemachi, Tomiokamachi, Iitatemura and Minami-Soma (see map below from Daily Yomiuri story, August 31). And it reinforces indications from the government that part of the 20 km no-entry zone will be closed permanently.
This is an important aspect of the evolving tragedy and comparisons with long-term evacuations in the case of Chernobyl are inevitable. So there is much speculation on the levels of contamination that will be deemed off-limits. There are 34 spots that meet the Chernobyl level for permanent evacuation (1.48 million becquerels of cesium 137 per square meter) – the white and red circles in the map below. Note that about half the sites lie outside the 20 km zone, with 8 located outside the 30 km zone.