我们从福岛核事故学到什么?

March 11th 2011 is a date etched into the minds of all Japanese.

Together the earthquake and tsunami cause a meltdown at the Fukushima Daiishi nuclear power plant in the northeast of the country.

James Acton is a nuclear expert at the Carnegie Endowment for International Peace. He describes the current situation in Fukushima.

"The worst of the accident by a long way is now over. The reactor operator has described the reactor as in cold shutdown. What they really mean by that is that radiation emitted from the plant has been brought down to near acceptable levels. The core of the reactor is less than 100 decrees Celsius. And barring a major accident, that situation is stable."

James Acton says Japan coped as well as could be expected -- under the circumstances.

"Now those circumstances were firstly the largest earthquake in Japan's history and a massive tsunami. And the operators were working under appalling conditions and proper plans for responding to an accident of this scale hadn't been developed. So there's a big criticism that those plans hadn't been developed but given they hadn't been developed I think people acted basically as well as they could under the appalling circumstances."

"What needs to be learnt from this accident?"

"Firstly there's very important lessons about hazard prediction. Japan was predicting a maximum 5.7 meter tsunami hitting the plant. It was actually a 13.1 meter tsunami. So we need to get better at hazard prediction. Secondly there's also lessons about reactor design, about protecting these key components that generate electricity to keep a plant cool, about designing them with greater redundancy. Thirdly there's lessons about responding to an accident. Those plans have to be developed well in advance and managed and practiced. You can't improvise once an accident happens."

"What does clean up mean?"

"There's a whole series of different challenges. Firstly the reactors have to be 100 percent stabilized and ultimately that's going to mean removing the melted fuel from the core if the reactor. That's a challenge that's going to take years and years and years. In addition all of the radiation on the plant site and in the area surrounding the plant site is going to have to be removed. And nobody has ever attempted a cleanup on this scale before. The previous nuclear accident that involved a large offsite release of radiation at Chernobyl, the authorities there just decided to declare an exclusion zone around the plant and haven't tried to clean it up. So Japan is approaching an unknown challenge. It's estimated that it's going to take 3-4 decades to complete the cleanup operation. The cost is unknown but I wouldn't be at all surprised if it was significantly in excess of, say, 100 billion dollars."

Japan generates around 30 percent of its energy from nuclear power. But most of its plants remain offline awaiting further safety tests following the Fukushima accident.

For CRI, I'm Dominic Swire.