TOKYO -- The UN's nuclear watchdog the IAEA warned Japan's nuclear crisis was "very serious" Wednesday as Tokyo resorted to increasingly desperate measures to cool overheated reactors and fuel pools at the stricken Fukushima plant.
International Atomic Energy Agency (IAEA) head Yukiya Amano confirmed reactors No. 1, No. 2 and No. 3. had partially melted down. He added that Japanese authorities had also reported concerns about the spent nuclear fuel pools of reactors No. 3 and No. 4.
The deep tanks contain used fuel rods which are extremely radioactive and normally kept immersed in cooling water. Unlike the fuel rods that are used in the reactor vessel, the spent rods are not surrounded by a steel-and-concrete containment vessel. If water in the pools evaporated, the spent rods would be exposed to the air and radioactive material would be released into the atmosphere.
Amano also announced he would travel to Japan as early as Thursday to observe the situation and report back first hand.
Earlier Wednesday, following the cancellation of a helicopter mission to pour water on No. 3 reactor due to high radiation levels, a water cannon normally used by riot police arrived at the plant to pump water into the spent fuel pool of No. 4 reactor.
The US military said it had delivered high-pressure water pumps to Japan to help with the operation at Fukushima.
"High-pressure water pumps were offloaded from USNS Safeguard in Yokosuka last night and delivered to Yokota Air Force Base for further transfer to the government of Japan for employment at the Fukushima power plant," the US Pacific Fleet said in a statement.
The US military also increased its own operational exclusion zone around the Fukushima plant to 50 miles. The Pentagon also confirmed some flight crews were issued with potassium iodide tablets to combat the possible effects of radiation.
Earlier US Energy Secretary Steven Chu told a House of Representatives hearing that the crisis appeared "to be more serious than Three Mile Island," referring to the 1979 accident in Pennsylvania.
French Industry Minister Eric Besson said the situation at the plant appeared to be getting out of control. "Let's not beat about the bush. They have visibly lost the essential control [of the situation]. That is our analysis, in any case, it's not what they are saying," Besson told French news channel BFM.
France, Europe's leader in nuclear power, earlier said its nationals should leave Tokyo, which is 155 miles (250km) south of the plant.
Besson's comments were echoed by the European Union's energy commissioner, Guenther Oettinger, who told a European Parliament committee the site was "effectively out of control."
"In the coming hours there could be further catastrophic events which could pose a threat to the lives of people on the island," he said.
The crisis has sparked international concerns over the safety of nuclear power, and French president Nicolas Sarkozy said he would call a special meeting of G-20 energy and economy ministers to discuss energy strategy. France holds the G-20 presidency.
Russia said it would begin evacuating dependents of its diplomatic and commercial personnel from Tokyo on Friday.
The Chinese government ordered safety inspections of all nuclear facilities in the wake of Japan's atomic crisis, and said it was freezing approval of all new plants. China is one of the fastest-growing consumers of nuclear power as it seeks to meet energy demands of its booming economy.
Japan's Chief Cabinet Secretary Yukio Edano, the government's spokesman, said radiation levels posed no immediate health threat outside a 12-mile (20-kilometer) exclusion zone that has already been evacuated.
Workers returned to the plant after an evacuation order due to a spike in radiation, although a spokesman for the embattled operator Tokyo Electric Power Co. (TEPCO), told Fox News the plant was never totally abandoned and workers outside were told to take cover indoors.
Edano later said that the alert was designated as a false alarm due to a misreporting of the radiation levels at the plant's gate. He said that a decimal point was placed incorrectly, giving a reading of 100 millisieverts instead of 10 millisieverts.
A single dose of 1,000 millisieverts -- or one sievert -- causes temporary radiation sickness such as nausea and vomiting.
Engineers have been battling a nuclear emergency at the 40-year-old plant since a 9.0-magnitude earthquake and tsunami -- which left more than 3,700 dead and thousands more unaccounted for across Japan -- knocked out cooling systems last Friday and fuel rods began overheating.
There have been four explosions and two fires at four of the plant's six reactors, releasing radioactive material into the atmosphere.
March 16, 2011, Pocno Record