Tokyo: The operator of Japan's tsunami-hit Fukushima nuclear power plant on Monday said the amount of radiation being emitted from the complex has halved from a month ago, in the latest sign that efforts to bring the plant under control are progressing.
The Fukushima Daiichi plant, 240 kilometres (150 miles) northeast of Tokyo, was damaged in March by a devastating earthquake and tsunami in the world's worst nuclear accident since the Chernobyl disaster 25 years ago.
"Our latest measurements show that radiation from the damaged reactors is 100 million becquerels per hour, which is one eight-millionth of the amount measured soon after the accident," Tokyo Electric Power's (TEPCO) vice president Zengo Aizawa told reporters during a monthly review.
Aizawa said that this translates to about 0.2 millisievert per year of radiation measured at the fringes of the plant, below the 1 millisievert safety limit according to government guidelines.
The amount is half of what TEPCO announced at its review a month ago.
In light of the progress being made in cooling its damaged reactors, which suffered nuclear fuel meltdowns in the first days of the crisis, TEPCO formally brought forward its plan to bring the plant to a state of "cold shutdown" within this year, instead of by January as initially planned.
It had said last month it was hoping to achieve a cold shutdown within the year but had not made a formal declaration.
Technically, a cold shutdown is a state in which water used to cool nuclear fuel rods remains below 100 degrees Celsius, preventing the fuel from reheating.
With the help of newly built cooling systems, TEPCO's efforts to cool the reactors have progressed steadily, with temperatures at all three of the damaged reactors falling below 100 degrees late in September.
But despite this development, TEPCO and the government have been cautious about immediately declaring a cold shutdown.
"We still need to proceed with care. We need to continue monitoring whether the temperatures of the reactors and radiation levels being emitted remain stable going forward," Yoshinori Moriyama, deputy director-general of the government watchdog Nuclear Industrial and Safety Agency, told the same news conference.
Declaring a cold shutdown will have repercussions well beyond the plant as it is one of the criteria the government said must be met before it begins allowing about 80,000 residents evacuated from within a 20 km (12 mile) radius of the plant to go home.
Japan faces a massive cleanup task if these residents are to be returned home -- the environmental ministry says about 2,400 square km (930 square miles) of land surrounding Daiichi may need decontamination, an area roughly the size of Luxembourg.
Even if a cold shutdown is declared TEPCO has acknowledged that it may not be able to remove the fuel from the reactors for another 10 years and that the cleanup at the plant could take several decades.
It also has to decontaminate tens of thousands of tonnes of contaminated water pooled at the plant, a result of its efforts to cool the reactors early in the crisis by pumping in vast amounts of water, much of it from the ocean.
First Published: Monday, October 17, 2011, 15:58