The "radius" approach, which doesn't make sense at all when you consider the radioactive materials being dispersed in the air, is set to be modified, though it will be continued to be used.
From Asahi Shinbun (5:00AM JST 4/11/2011):
The Kan Administration has decided on the new policy to issue orders for evacuation in the areas outside the 20-kilometer radius from the Fukushima I Nuke Plant which have high cumulative radiation. The new policy will be announced as early as today (April 11). Some areas between 20 to 30-kilometer radius ("stay indoors") and some areas outside the 30-kilometer radius are to join the evacuation zone.
The areas that will be newly designated as "evacuation zone" are the areas whose cumulative radiation level is expected to exceed 20 milli-sieverts per year, and they will be called "planned evacuation zone". The residents will have about 1 weeks to prepare, and they will be evacuated by buses prepared by the government. The new "planned evacuation zone" will not form a concentric circle like the evacuation zone that has been in place, but will be like a mosaic.
The current "evacuation zone" within the 20-kilometer radius will become the "warning zone" under the Basic Emergency Measures, and entering the zone will be prohibited, while allowing the residents to temporarily return home on certain conditions. Chief Cabinet Secretary Yukio Edano told the press on April 10 that the "warning zone" was "in the final stage of planning. [We will be able to tell you about it] in not too distant future."
That "temporary return", they're talking about 1 or 2 hours for the residents to collect the absolute minimum from their homes. This is after the government sent out scholars and researchers in the cities and towns affected by the Fukushima I Nuke Plant accident to convince the residents not to worry about radiation and radioactive materials.
The cumulative radiation of 20 milli-sievert was what the Nuclear Safety Commission (not the Agency) had been advising the government to adopt as one of the criteria in deciding whether to evacuate the residents.
As I posted before, the radiation level in part of a town (Namie-machi) at about 30 kilometers northwest of the Fukushima I Nuke Plant is already at 11.63 milli-sieverts, cumulative over 13 days ending April 5. That number seems to measure only external exposure.
In the meantime, the news on the MSM in Japan is scrubbed almost clean. Yomiuri's site right now has only one headlines at the top that is related to Fukushima I Nuclear Power Plant, that the TEPCO's president is visiting Fukushima to apologize. Asahi has a report on a family who lived next to Fukushima I Nuke Plant, but the rest of the news are about the local elections and Masters' golf. It's similar with other major papers.
Fukushima I Nuke Plant accident is a minor nuisance, or is treated as such both by the government and the media. Never mind that TEPCO or Nuclear and Industrial Safety Agency doesn't seem to have a clue as to what to do and how to do it. If you don't report it, it doesn't exist.