Japanese engineers conceded on Friday that burying a crippled nuclear plant in sand and concrete may be the only way to prevent a catastrophic radiation release, the method used to seal huge leakages from Chernobyl in 1986.
Officials said they still hoped to fix a power cable to at least two reactors to restart water pumps needed to cool overheating nuclear fuel rods. Workers also sprayed water on the No.3 reactor, one of the most critical of the plant's six.
It was the first time the facility operator had acknowledged that burying the sprawling complex was an option, a sign that piecemeal actions such as dumping water from military helicopters were having little success.
"It is not impossible to encase the reactors in concrete. But our priority right now is to try and cool them down first," an official from the plant operator, Tokyo Electric Power Co, told a news conference.
As Japan entered its second week after a 9.0-magnitude earthquake and 10 meter (33-foot) tsunami flattened coastal cities and killed thousands of people, the world's worst nuclear crisis since Chernobyl looked far from over.
Millions in Tokyo remained indoors on Friday, fearing a blast of radioactive material from the complex, 240 km (150 miles) to the north, although prevailing winds would likely carry contaminated smoke or steam away from the densely populated city to dissipate over the Pacific Ocean.