Via NHK News :
" Nuclear experts are suggesting the government revise the radioactive standards for evacuation advisories involving the emergency at the Fukushima Daiichi nuclear power plant.
The move comes almost 4 weeks after tsunami disabled the nuclear plant.
According to existing guidelines, people should remain indoors when radiation levels outdoors reach 10 millisieverts several days after any accident. Evacuation is only considered when levels reach 50 millisieverts. The guidelines were set by the Nuclear Safety Commission using standards adopted by organizations including the International Atomic Energy Agency.
The government has advised residents living in areas within 20 kilometers of the Fukushima Daiichi nuclear power plant to "evacuate" while those in areas between 20 and 30 kilometers have been told to "stay indoors".
However, the amount of exposure is likely to rise in these areas as little progress has been made in cooling the nuclear fuels or containing radiation leaks."