By Martyn Williams
Japan has raised its evaluation of the Fukushima Daiichi nuclear disaster to the highest level on the international nuclear accident scale — level seven.
The upgrade makes Fukushima only the second nuclear accident ever to rank at level seven. The other was the 1986 Chernobyl disaster.
But Japanese government says, despite the similar rankings, the severity of the the two accidents is different. The amount of radiation released is so far only a tenth that of Chernobyl and there have been no radiation-related deaths in Japan.
Radiation is still coming out of the damaged Fukushima plant, but the level measured in the surrounding area has been declining.
The government asked people living within 20 kilometers of the plant to evacuate on the second day of the crisis. On Monday — a month to the day after the great quake and tsunami that triggered the problems — the government advised people living in several communities to the northwest of the power station to prepare to leave.