Tokyo:
Workers at Japan's crippled nuclear plant piled up sandbags and readied emergency storage tanks on Tuesday to stop a fresh leak of highly contaminated water from reaching the ocean, opening up another front in the battle to contain the world's worst nuclear accident in decades.
As fears of further contamination grew, Prime Minister Naoto Kan said his government was in a state of maximum alert over the situation at the Fukushima Daiichi Nuclear Power Station.
The Japanese government said the discovery of plutonium in the soil near the plant provided new evidence that the fuel in at least one of the plant's reactors had experienced a partial meltdown. A full meltdown of the fuel rods could release huge amounts of radiation into the environment.
"There is a high possibility that there has been at least some melting of the fuel rods," said Yukio Edano, the government's chief spokesman. "That in itself is a very serious situation," he said.
"This quake, tsunami and the nuclear accident are the biggest crises for Japan" in decades, Mr. Kan said in Parliament.
Mr. Kan defended his visit to a nuclear power plant crippled by a tsunami earlier this month. Responding to questions for the first time since the March 11 earthquake and tsunami hit northeast Japan, Mr. Kan acknowledged that the crisis at the plant gave little cause for optimism.
Mr. Kan toured the plant the day after the tsunami, and some lawmakers have suggested his presence delayed efforts by the plant operator to immediately confront the emergency.
He said his March 12 visit was not a "political performance," the Kyodo news service reported.
"Grasping the situation at the plant at that time was extremely important," he said.
French President Nicolas Sarkozy is scheduled to meet the embattled prime minister on a visit to Japan Thursday, the French leader's office said. Mr. Sarkozy will travel to Japan on behalf of the Group of 20 leading world economies. Mr. Sarkozy's visit will be separate from a trip by French nuclear experts, who will consult with the operator of the Fukushima plant.
Efforts to contain the unfolding crisis at the plant, ravaged in the quake and tsunami, have focused on restoring power and restarting the cooling systems at the plant's six reactors, while keeping the nuclear fuel rods cool in the meantime with fire hoses and pumps.
But in the past days, work at the plant's most severely damaged reactors, Nos. 1 through 3, has slowed, after the discovery of highly radioactive water around and inside the reactor buildings. Last week, three workers were injured after stepping into radioactive water at Reactor No. 3. The water has now accumulated inside the turbine buildings of the three reactors and is now making its way through separate underground tunnels to openings just 200 feet from the sea, officials say.
A leak of the radioactive water, which measured more than 1,000 millisieverts an hour on the surface at Reactor No. 3, could exacerbate smaller leaks of radiation detected in the seawater around the plant. Contaminated water was also found at tunnels from the No. 1 and No. 3 reactors, though with much lower levels of radiation. Officials have said that the water is likely leaking either from broken pipes inside the reactor, or from a breach in the reactor's pressure vessel, which houses the nuclear fuel.
On Tuesday, workers piled sandbags outside the opening of one tunnel in danger of overflowing near Reactor No. 1, according to the plant's operator, Tokyo Electric Power Company. They also prepared to pump water out of the turbine buildings, and to secure storage tanks to hold the highly radioactive water.
But capacity may be running out, officials said. At Reactor No. 3, for example, a 750-gallon tank inside the reactor building is already full, while a smaller tank is more than half full. "When there is no more room in the tanks," said Hidehiko Nishiyama, a top official at Japan's nuclear regulator, "we will need to think of another option."
Radioactive leaks at the plant have become a growing concern. Shipments of milk, spinach and other agricultural produce were banned last week after tests showed higher-than-normal amounts of radioactive iodine 131 and cesium. Tokyo briefly advised that infants not drink tap water after the radioactive iodine was detected in the city's water supply.
Last week, the Institute for Energy and Environmental Research, an independent think tank in the United States, said that since the quake and its aftermath, the plant has already released far more radioactivity than the 1979 Three Mile Island accident. The institute, based in Takoma Park, Maryland, said that by March 22, the Fukushima reactors had released about 2.4 million curies of iodine 131, about 160,000 times the best estimate of the amount released at Three Mile Island, and about 10 percent of the amount released in Chernobyl in 1986. Fukushima Daiichi has also released half-a-million curies of cesium-134 and cesium-137, which have longer half lives, also about 10 percent the amount released in Chernobyl.
"While the releases are still considerably below Chernobyl, they have already reached a level that could affect the region around the site for a prolonged period," Arjun Makhijani, the institute's president, said in a statement.
Concerns over the leaks took on an added urgency late Monday, as Tokyo Electric Power announced it had found traces of plutonium in the plant's soil. The plutonium levels detected were not a risk to humans, but the development added urgency to regain control of the plant, Mr. Edano said Tuesday.
It was unknown where the plutonium had come from. The reactors could be a source, and tests of nuclear weapons in the atmosphere, which ended in 1980, left trace amounts of plutonium around the world. The highest levels in the soil were found about 500 yards from the most heavily damaged reactors, the company said.
All the reported readings are within the safe range of plutonium levels in sediment and soil given by the United States Agency for Toxic Substances and Disease Registry. But Tokyo Electric Power said the highest reading was more than three times the level found in Japan compared with the average during the past 20 years.
The challenge now, Mr. Edano said, is to keep pumping enough water to ensure that fuel rods do not overheat while at the same time trying to minimize the overflow of contaminated water.
All three kinds of nuclear fuel at the complex could leak plutonium. Reactor No. 3 is fueled partly by mixed oxide fuel, or mox, which is made from plutonium and uranium. Most reactor fuel is uranium.
Mr. Nishiyama, who is deputy director general for the Nuclear and Industrial Safety Agency, said that while the detected plutonium levels were low, they pointed to the gravity of the crisis at the complex. Plutonium is a heavy element and not easily dispersed, he said, so higher levels outside the reactor suggested a wider leak.
"This detection from the soil speaks to the importance and seriousness of the situation," Mr. Nishiyama said.
The government's official death toll from the quake and tsunami rose above 11,000 on Tuesday, with more than 17,000 listed as missing.