Cumulative Annual Radiation Doses Calculated

I didn't look up the direct link, but this should indicate to the slow-to-act that a wider evacuation is needed.

http://mdn.mainichi.jp/mdnnews/national/news/20110427p2a00m0na015000c.html

The Japanese government unveiled a map of radioactive contamination on April 26, predicting residents in areas near the troubled nuclear power plant could be exposed to radiation far greater than permissible levels.

According to the contamination map unveiled by the Ministry of Education, Culture, Sports, Science and Technology, a cumulative dose of radiation for the year to March 11, 2012 is expected to reach 235.4 millisieverts in Akogi Kunugidaira in Namie, Fukushima Prefecture, 24 kilometers northwest of the Fukushima No. 1 Nuclear Power Plant.

The cities of Fukushima and Minami-Soma are also predicted to receive more than 10 millisieverts of radiation, 10 times the dose of artificial radiation an ordinary person is allowed to be exposed to a year.

Based on data collected from 2,13...8 monitoring points, the ministry calculated total cumulative doses of radiation between March 12 and April 21 and added them up to expected cumulative doses of radiation for the period thereafter to March 11, 2012. Expected radiation exposure was based on the assumption that the nuclear power plant continues to spew the same level of radiation as that detected on April 22. The ministry assumed that people in each monitoring point spend eight hours outdoors and 16 hours inside wooden houses a day. The ministry assumes the level of exposure to radiation in wooden houses is 40 percent lower than outdoors.

As a result, higher levels of radiation were predicted in areas northwest of the nuclear power plant. On April 11, the government designated areas outside a 20-kilometer radius of the nuclear plant that were expected to receive 20 millisievers per year as "planned evacuation zones." Ten locations in the zones including Namie, Iitate and Kawamata were predicted to receive more than 20 millisieverts of radiation. Ryozen in Date, 48 kilometers northwest of the nuclear plant, was predicted to receive 21.2 millisieverts per year.

The ministry had unveiled a similar map on April 11, but the map released this time predicted radiation levels in wider areas based on larger quantities of data. The ministry plans to update the map regularly and release it twice a month.