Kan said that once the situation has been contained to some degree, then officials will have to analyze why the accident has gotten bigger and bigger. By studying that, he said Japan will have to consider what measures can be taken to prevent a recurrence, and this should be agreed upon internationally.

An extra 20 French nuclear technicians are arriving in Japan to help tackle the crisis at the Fukushima plant.

France, which this year is chairing the Group of 20 economic powers, is the world's most nuclear-dependent country, producing 75 percent of its electricity from 58 reactors.

Sarkozy said those calling for all nuclear power plants to be shut down in the wake of the Fukushima crisis should be more realistic.

He said everyone is working hard to reduce CO2 emissions from power generation. But there are not hundreds of solutions to reduce emissions, he said, and that is why this is not a question of choice, but of nuclear safety, because there is no alternative. He also said alternative energy plans cannot replace nuclear power plants, so safety standards must be strengthened.

In the ocean next to the Fukushima power plant, technicians are reporting the highest levels of radiation yet, about 4,385 times higher than the legal limit.

Japan’s nuclear safety agency insists this poses no danger to human health, however, as everyone has been evacuated from the vicinity and fishing in the area is banned.