Japanese Prime Minister Yoshihiko Noda says the nuclear plant crippled by the March 11 tsunami has reached a state of “cold shutdown”, in a major step in efforts to bring Japan's worst nuclear disaster under control.

Mr. Noda made the announcement about the stricken Fukushima nuclear plant on Friday, saying the crisis that began nine months ago is now over.

“Members of the Nuclear Emergency Response Headquarters, which I chair, met today and confirmed that the (Fukushima Dai-ichi nuclear power plant) reactors have reached a state of cold shutdown, and that the accident at the nuclear power plant itself is now over. I hereby declare that Phase 2 in the roadmap to bring the accident under control is now complete.”

A cold shutdown means the three damaged reactors have been stabilized and are no longer leaking substantial amounts of radiation nor are in danger of going critical.

But some experts fear that the facility is still contaminated with high levels of radiation.

Junicho Sato, a spokesman for the environmental group Greenpeace, charged that the government's statement was premature.

“The radiation is escaping from the site even now, and tons of people are still suffering from radiation risks, so I cannot actually believe the government is going to say (this). This is not cold shutdown, this is still disaster and the government has to prioritize the people's safety before the political performance.”

Stabilization of the reactors, whose molten cores spewed radioactive particles into the air and sea, marks the end of the second step of the clean-up. Step three involves the decommissioning of the damaged units, a process experts expect to last up to 40 years.

Mr. Noda acknowledged to reporters that billions of dollars will be needed to compensate the tens of thousands of people forced to evacuate their communities and the numerous ruined businesses, including farms and fishing fleets.

There is also concern about the possibility of another huge quake or tsunami causing further serious damage and radiation releases. Authorities in Japan say that is extremely unlikely. But critics point out that the Tokyo Electric Power Company and the government had brushed off warnings that a natural disaster could trigger multiple reactor meltdowns at Fukushima prior to the March 11 earthquake and tsunami.