Japanese officials grappling on Sunday to end the world's worst nuclear crisis since Chernobyl tried to seal a crack that has been leaking radiation into the ocean from a crippled reactor.
An aide to embattled Prime Minister Naoto Kan said the government's main task now was to stop the radiation leaks that are spooking the population and scaring away tourists.
"We have not escaped from a crisis situation, but it is somewhat stablised," said Goshi Hosono, a ruling Democratic Party lawmaker.
Tokyo Electric Power Co (TEPCO) said it had found a crack in a concrete pit at its No 2 reactor in Fukushima on Saturday, generating readings 1,000 millisieverts of radiation per hour in the air inside.
The leaks did not stop after concrete was poured into the pit, and TEPCO was turning to water-absorbent polymers to prevent any more contaminated water from going out.
"We are hoping that the polymers will absorb water and fill in the pipe to prevent water from flowing," said Hidehiko Nishiyama, deputy director general of the Nuclear and Industrial Safety Agency (NISA).
He said the latest effort to staunch the flow of radioactive water into the Pacific would start on Sunday afternoon and that workers would top the polymers with more concrete to hold in the water.
Nishiyama told reporters on Saturday that the crack "could be one source" of the radiation leaks that have hobbled efforts to quell the damaged reactor.
On Sunday he added, "This (crack in the pit) for the first time clarified the relationship (of the contaminated water) with the sea."
Officials from the utility said checks of the other five reactors found no cracks.
Nishiyama said that to cool the damaged reactor, NISA was looking at alternatives to pumping in water, including an improvised air conditioning system, spraying the reactor fuel rods with vaporized water or using the plant's cleaning system.
PM under pressure As the disaster that has left more than 27,000 dead or missing dragged into a fourth week, Kan toured devastated coastal towns in northern Japan on Saturday, offering refugees government support for rebuilding homes and livelihoods.
"It will be kind of a long battle, but the government will be working hard together with you until the end," Kyodo news agency quoted him as telling people in a shelter in Rikuzentakata, a fishing port flattened by the tsunami which struck on March 11 after a massive earthquake.
Unpopular and under pressure to quit or call a snap poll before the disaster, Kan has been criticised for his management of the humanitarian and nuclear crisis. Some tsunami survivors said he came to visit them too late.
Kan also entered the 20-km (12-mile) evacuation zone and visited J-village just inside the zone, a sports facility serving as the headquarters for emergency teams trying to cool the six-reactor Fukushima Daiichi plant.
Operators of the plant are no closer to regaining control of damaged reactors, as fuel rods remain overheated and high levels of radiation are flowing into the sea.
Japan is facing a damages bill which may top $300 billion -- the world's biggest from a natural disaster.
The International Monetary Fund (IMF) said on Friday the Japanese economy would take a short-term hit and it could not rule out further intervention for the yen.
The consequences for the world's third largest economy have already seen manufacturing slump to a two-year low. Power outages and quake damage have hit supply chains and production.
Farmers in the countryside surrounding the reactor are fretting that consumers in Japan will reject their crops.
"Grown in Fukushima" has become a warning label for those nervous of radiation which has already been found in some vegetables close to the nuclear plant savaged by last month's earthquake and tsunami.
"There is no way we will be able to sell anything," said 73-year-old farmer Akio Abiko. "People in Tokyo are just too sensitive about this kind of thing."
A group of farmers came to Tokyo from Fukushima at the weekend, using Geiger counters to show their produce was safe.
Hundreds of thousands remain homeless, sheltering in evacuation centres, as the death toll from the disaster rises.
Civil servant Takako Suzuki, 40, told Reuters she spent the night after the tsunami huddled with 11 other people in deep water on the third floor of an evacuation center amid bodies and falling rubble. As many as 100 people fled a 14 metre (42 ft) wave in that building, but only Suzuki and 10 others lived.
Thousands of Japanese and US soldiers on Saturday conducted a search for bodies using dozens of ships and helicopters to sweep across land still under water along the northeast coast. The teams hope when a large spring tide recedes it will make it easier to spot bodies.
Radiation 4,000 times the legal limit has been detected in seawater near the Daiichi plant and a floating tanker was to be towed to Fukushima to store contaminated seawater. But until the plant's internal cooling system is reconnected radiation will flow from the plant.