The reactor accident at Fukushima has caused a few Japanese to have a moving experience. I have seen estimates of 70,000 so far. But the moving may not be over.
Tetsuji Imanaka, an associate professor of nuclear engineering at the Kyoto University Research Reactor Institute, Satoru Endo, an associate professor of radiation physics at Hiroshima University, and other experts visited Iitate in late March.There are danger zones outside the 30 km zone already designated a "stay indoors" zone. And of course inside the 20 km zone is an exclusion area.
They collected soil samples from five locations in the village at depths of five centimeters. All the locations were outside the 30-km radius and were by roadways in various hamlets.
The study found cesium-137 at levels between about 590,000 and 2.19 million becquerels per cubic meter.
After the Chernobyl nuclear accident in the former Soviet Union in 1986, residents who lived in areas where cesium-137 levels exceeded 555,000 becquerels were forced to move elsewhere.
According to a report by the International Atomic Energy Agency, the total land area from where residents were forced to move was about 10,000 square kilometers, about the land area of Gifu Prefecture. A total of about 270,000 residents were subject to the forced move.
The amounts of cesium-137 found in Iitate were at most four times the figure from Chernobyl.
If more radioactive materials are emitted from the crippled Fukushima plant, the level of cesium-137 could rise even further.
The central government is considering using an accumulated radiation exposure figure of 20 millisieverts over the course of a year as one indicator of whether an evacuation instruction should be issued.The 20 millisievert per year dose limit is the International dose limit. That would be 2.3uSv per hour averaged over a year.
It looks like a few more people are going to be moved. How soon? It depends on the Japanese government. There is no rush. The Japanese government has a few other pressing problems to deal with. Like the homeless from the earth quake. They can wait a bit to add a few hundred thousand more to that number.