crack in a concrete pit that is leaking highly radioactive water into the ocean from a crippled reactor.

Japanese officials grappling to end the nuclear crisis at the earthquake and tsunami-damaged Fukushima plant are focusing on a crack in a concrete pit that is leaking highly radioactive water into the ocean from a crippled reactor.

Power plant workers attempted to fill the shaft with fresh concrete on Saturday, but that did not change the amount of water coming out of the crack, spokesmen for Tokyo Electric Co (TEPCO) told a news conference.

They will try to block the leak again on Sunday by injecting polymeric material into the trench and use additional concrete to prevent contaminated water from leaking into the sea.

A Tokyo Electric expert will visit the site on Sunday and decide what polymer to use before the work begins.
The water has been leaking into the sea from a 20-centimetre crack detected at a pit in the reactor where power cables are stored, the government's nuclear safety agency said.

TEPCO said the pit is connected to the No. 2 reactor's turbine building and a tunnel-like underground trench, in which highly radioactive water has been spotted so far.

Hidehiko Nishiyama, deputy head of the Nuclear and Industrial Safety Agency (NISA), said on Saturday 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 vapourised water or using the plant's cleaning system.

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.

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.

Meanwhile TEPCO announced that two of its workers were killed by the tsunami that followed the March 12 earthquake, confirming the first deaths at the complex.

"It pains me that these two young workers were trying to protect the power plant while being hit by the earthquake and tsunami,'' TEPCO Chairman Tsunehisa Katsumata said in a statement on Sunday.

Their bodies, discovered just last week, had to be decontaminated due to radiation coming from the damaged reacto