After helicopters robotic arm tries to cool nuclear reactor

Fukushima, Japan: A 50-metre-long robotic arm sprayed water on a dangerously hot spent fuel pool as workers at Japan's crippled nuclear plant rushed to hook up power lines to all six reactors.

The specialised arm was brought in on Tuesday to help firefighters battling to keep the spent fuel rods and the reactors themselves cool at the Fukushima Dai-ichi nuclear power plant.

The emergency crews dumped 18 tonnes of seawater into the storage pool holding spent nuclear fuel at the number 4 reactor.

Steam, possibly carrying radioactive elements, had been rising for two days from the reactor building and the move lessens the chances that more radiation will seep into the air.

With the power lines connected, officials hope to start up the overheated plant's crucial cooling system that was knocked out during the March 11 tsunami and earthquake.

Tokyo Electric Power Company warned that workers still need to check all equipment for damage first before switching the cooling systems - a process that could take days or even weeks.

Late Tuesday night, Tokyo Electric said lights went on in the central control room of unit 3, but that doesn't mean power had been restored to the cooling system.

Officials will wait until sometime on Wednesday to try to power up the water pumps to the unit.