Tokyo - The tsunami-devastated Fukushima Dai-ichi nuclear power plant has reached a "cold shutdown" and is no longer leaking substantial amounts of radiation, Japan's prime minister said Friday.

Prime Minister Yoshihiko Noda's announcement marks a milestone nine months after the March 11 tsunami sent three reactors at the plant into meltdowns in the worst nuclear crisis since Chernobyl.

"Even if unforeseeable incidents happen, the situation is such that radiation levels on the boundary of the plant can now be maintained at a low level," Noda said at the government's nuclear emergency response meeting.

However, experts noted that the plant remains vulnerable to more problems and will take decades to decommission the plant.

Located 150 miles northeast of Tokyo, the plant was wrecked on March 11 by a huge earthquake and a tsunami that exceeded 45 feet in some areas, which knocked out its cooling systems, triggering meltdowns and radiation leaks.

The crisis displaced some 100,000 people. Officials are to start discussing allowing some residents to return to less contaminated areas. A 12-mile zone around the plant is expected to remain mostly off-limits for years.