Nuclear officials say they may seek U.S. and Japanese military help to spray water from helicopters onto an overheating spent fuel storage pool.
Tokyo Electric Power says it may use helicopters because of the risk of radiation contamination from approaching the pool directly. Air drops may also be more effective.
A Japanese official says the pool might be boiling, raising the risk that water used to keep the fuel cool might evaporate.
Officials are struggling to address the failure of safety systems at several of the plant's reactors after Friday's earthquake and tsunami.
Hundreds of aftershocks have shaken the region and Tokyo since, including one on Tuesday night whose epicentre was hundreds of kilometres southwest and inland from the original offshore quake.
Low on supplies
Canned goods, batteries, bread and bottled water have vanished from store shelves and long lines of cars circle gas stations, as Japan grapples with a new risk set off by last week's earthquake, tsunami and ensuing nuclear crisis — panic-buying.
Far outside the disaster zone, stores are running out of necessities, raising government fears that hoarding may hurt the delivery of emergency food aid to those who really need it.
“The situation is hysterical,” said Tomonao Matsuo, spokesman for instant noodle maker Nissin Foods, which donated a million items including its “Cup Noodles” for disaster relief.
The frenzied buying is compounding supply problems from damaged and congested roads, stalled factories, reduced train service and other disruptions caused by Friday's earthquake and the major tsunami it generated.
Renho, the Minister in charge of consumer affairs, who goes by one name, asked people to refrain from buying items they don't really need.