Japan has declared that its tsunami-stricken Fukushima nuclear power plant has reached cold shutdown, passing a key milestone in efforts to bring under control the world's worst nuclear accident since Chernobyl 25 years ago.
"The reactors have reached a state of cold shutdown," Yoshihiko Noda, Japan's prime minister, said at the government's nuclear emergency response meeting on Friday.
"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," he said.
"The government is due to set a clear road map and will do the utmost to decommission the plant," the Japanese PM said.
The Fukushima Daiichi plant, 240km northeast of Tokyo, was damaged on March 11 by a devastating earthquake and a 10-metre-high tsunami, which damaged its cooling systems, triggering meltdowns and radiation leaks.
Declaring a cold shutdown will have repercussions well beyond the plant: it is a government pre-condition before it allows about 80,000 residents evacuated from within a 20km radius of the plant to return home.
A cold shutdown is when water used to cool nuclear fuel rods remains below its boiling point, preventing the fuel from reheating. One of the chief aims of the plant's operator, Tokyo Electric Power Company (TEPCO), had been to bring the reactors to cold shutdown by the year-end.
After months of efforts, the water temperature in all three of the affected reactors fell below boiling point by September, but TEPCO has been cautious of declaring a cold shutdown, saying it had to see if temperatures and the amount of radiation emitted from the plant remained stable.
In an interview with Al Jazeera, Imad Khadduri, a nuclear scientist, said: "The Japanese PM’s plans are very formidable and very ambitious and detailed. And one measure of the success of this plan of decontamination can be juxtaposed against the efforts since March when the accident happened.
"I am very hopeful that the decontamination will be done in a very meticulous and rigorous manner unlike that of the Chernobyl in Russia nearly 25 years ago," he said.
Khadduri said: "The nuclear power plants, in fact, are large stainless steel eggs under huge pressure, almost 72 times the atmospheric pressure. And by cold shutdown, they mean that the pressure inside the plant has been brought down to the atmospheric level.
"In the past more than eight months, they have managed to reduce the temperature of fuel elements to under 95 degrees celsius, which is equal to the atmospheric pressure.
"Decommission means: They can remove the top part of the stainless steel egg and take out nuclear fuel elements, store them safely and starting to dissemble the plant and tube them with concrete materials."
He further added: "These [highly radioactive nuclear fuels] are stored at radio-established spent fuel storage tanks. These can be stored at nearly 54 other nuclear power stations that have large capacity for spent fuel storage."
TEPCO said early in the crisis that it did not plan to entomb the damaged Daiichi reactors in concrete, the option chosen at Ukraine's Chernobyl where reactors caught fire and burned for days. Instead, it favoured the gradual removal of the nuclear fuel for storage elsewhere.
The government and TEPCO will aim to begin removing the undamaged nuclear rods from Daiichi's spent fuel pools as early as next year. However, retrieval of fuel that melted down in their reactors may not begin for another decade, with the complete dismantling of the plant expected to take up to 40 years, domestic media reported on Thursday.
The enormous cost of the cleanup and compensating the victims of the disaster has drained TEPCO financially. The government may inject about $13bn into the company as early as next summer in a de facto nationalisation, sources told the Reuters news agency last week.
Japan also faces a massive cleanup task outside the plant if residents are to be allowed to return home. The environment ministry says about 2,400sq km of land around the plant may need to be decontaminated.
The crisis shook the public's faith in nuclear energy and Japan is now reviewing its earlier plan to raise the proportion of electricity generated from nuclear power to 50 per cent by 2030 from 30 per cent in 2010.
Living in fear of radiation is part of life for residents both near and far from the plant. Cases of excessive radiation in vegetables, tea, milk, seafood and water have stoked anxiety despite assurances from public officials that the levels detected are not dangerous.
Chernobyl's experience shows that anxiety is likely to persist for years to come, with residents living near the former Soviet plant still regularly checking local produce for radiation before consuming them 25 years after the disaster.
The announcement may not dramatically improve Noda's support ratings, eroded by his steadfast commitment to a sales tax increase to cope with a public debt burden twice the size of Japan's economy.
Noda is also faced with a formidable list of other tasks, such as helping a stagnant economy deal with the yen's rise to historic highs.