Preparing for the worst-case scenario of a meltdown at Shikoku Electric Power Co.'s Ikata nuclear plant, Ehime Prefecture held its first emergency drill Tuesday to test the response to a massive leak of radioactive materials.

Kagawa, Kochi, Tokushima, Yamaguchi and Oita prefectures also participated in the drill.

Under the exercise, a massive plume of radioactive materials leaked from reactor 3 at the Ikata plant after it was hit by an earthquake. An evacuation order was issued for people living within 30 km of the plant as radiation readings above the government-set limit of 500 microsieverts per hour were detected.

Participating residents evacuated to civic centers and other places outside the 30-km radius, and officials on a crisis management headquarters in Matsuyama City Hall teleconferenced with Yamaguchi and other prefectural officials.

Ambulances and helicopters were mobilized to take injured plant workers to hospitals, while the prefecture screened residents for radiation exposure.

In June, Ehime Prefecture established a 30-km radius around the Ikata plant as the priority zone for nuclear disaster prevention measures. The zone covers seven towns and cities in Ehime Prefecture, including the town of Ikata, as well as part of Kaminoseki, Yamaguchi Prefecture.