At the same time the International Atomic Energy Agency (IAEA) said it does not at the moment have health concerns either in Japan or more widely from released radiation, although that could change if the situation worsened.

On a flying visit to Tokyo, IAEA Director General Yukiya Amano met with Prime Minister Naoto Kan, other ministers and TEPCO electricity company officials to discuss how the agency can help mitigate the crisis caused by loss of power to the reactor cooling systems when the Fukushima Daiichi nuclear power plant was damaged by a devastating earthquake and tsunami a week ago.

“The director general stressed the importance of providing faster and more detailed information about the situation at the nuclear power plants including to the international community,” IAEA Special Adviser on Scientific and Technical Affairs Graham Andrew told a news briefing at agency headquarters in Vienna, at which he reported that, as yesterday, the situation remains very serious but with no significant worsening.

“He also emphasized the importance of Japan working closely with the international community to resolve the crisis,” Mr. Andrew said, adding that the Japanese affirmed their willingness to strengthen their cooperation with the agency.

IAEA has sent a monitoring mission to Japan, which at the moment is focusing on radiation levels in Tokyo, where first measurements show no indication of iodine-131 or caesium-137, major radioactive hazards present in nuclear fission products. A second sampling was to be carried out overnight. “We will move towards the Fukushima region as soon as possible,” Mr. Andrew said.

“We don’t have concerns at the moment both in Japan and, if not in Japan, clearly more widely for human health. If the situation changed dramatically, then we’d have to make a reassessment.”

He noted that the UN International Civil Aviation Organization (ICAO) said today that international flights and maritime operations can continue normally into and out of Japan’s major airports and seaports and that there is no medical basis for imposing additional measures to protect passengers.

On the situation at the Fukushima reactor site, more than 200 kilometres to the north of Tokyo, Mr. Andrew noted that spent fuel ponds at units three and four of the six-unit plant remain “an important safety concern,” with information lacking on cooling water levels and temperatures. As for the first three units, perhaps half of the fuel in some cases is uncovered, “which is not positive,” he said.

“We want all of the fuel to be covered, but it’s not oscillating, it’s not going down dramatically. So certainly for the units one, two and three the situation, taking on board the pressure and the water levels, remains fairly stable, which is positive,” he added.