Japanese authorities have classified the Fukushima nuclear accident as a level 4 disaster, with 7 being the worst.

Japanese authorities have classified the Fukushima nuclear accident as a level 4 disaster, with 7 being the worst.

The disaster rating was announced even as a Ukrainian nuclear expert warned that the explosion at the plant could be as dangerous as the 1986 Chernobyl disaster.

The Chernobyl meltdown was given a 7.

According to the international rating system, a level 3 would affect the health of the workers in the plant. A level 4 would mean minor radiation, causing death of those who work in the plant, Xinhua reports.