"Pollution levels are low, and such territories are easy to rehabilitate," said Rafael Arutyunyan, first deputy director of Russia's nuclear safety problems institute. "I think it will be clear in five years, and people will live there."

He also said Japanese nuclear specialists will have to build a protective cover for the damaged reactors. According to his estimates, radiation levels in the reactor vault may range from 5,000 to 6,000 roentgen per hour.

"Clearly, the Japanese will have to build a cover of some sort," the Russian expert said.

Operations have continued to restart the cooling systems at Fukushima's six reactors to try to avoid a major radioactive release.

The Japanese government on Friday asked people still living within 30 km of the damaged plant to leave due to shortages of food and other essentials.

Food, water and fuel in prefectures around Fukushima are in short supply over contamination fears, while countries including the United States, Russia and Australian have banned the imports of food products from Fukushima, Ibaraki, Tochigi and Gunma prefectures.