VIENNA (Reuters) - The U.N. atomic agency said on Friday conditions at a damaged Japanese nuclear power plant were grave but not deteriorating badly.
"The situation at Fukushima Daiichi nuclear power plants remains very serious but there has been no significant worsening since our last briefing" on Thursday, Graham Andrew, a senior official of the International Atomic Energy Agency (IAEA), said.
"The situation at the reactors at units 1, 2 and 3 appears to remain fairly stable."
He was speaking after Japanese engineers conceded that burying the crippled plant in sand and concrete may be a last resort to prevent a catastrophic radiation release, the method used to seal leakages from Chernobyl in 1986.
They still hoped to solve the crisis by fixing a power cable to two reactors to restart water pumps needed to cool overheating nuclear fuel rods.
Work on this continued, Andrew said, adding: "Another positive development is that diesel generators are providing power for cooling for both units 5 and 6."
He said officials were still concerned about pools holding spent fuel at reactor units 3 and 4. "Reliable, validated information is still lacking on water levels and temperatures at the spent fuel ponds," he said.
The IAEA was getting information on radiation levels in 47 Japanese cities and finding no health threats so far.
"Dose rates in Tokyo and other cities remain far from levels which would require action. In other words they are not dangerous to human health," Andrew said.
In Tokyo, IAEA Director General Yukiya Amano met Japan's prime minister, other senior officials and the vice president of plant operator Tokyo Electric Power Co (TEPCO).
"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," Andrew said, adding Japanese counterparts had agreed to this.
He said international organisations had found flight and maritime operations can continue normally into and out of Japan's major air and sea ports and there was no medical basis for imposing additional measures to protect passengers.
(Reporting by Michael Shields; Editing by Sophie Hares)