It is the latest in a string of measures aimed at stabilising the facility, where the biggest nuclear accident for a quarter of a century has unfolded over the past week.
The attachment of power cables to the No 1 and No 2 reactors' cooling systems may, however, prove futile if the pumps were damaged in the March 11 earthquake and tsunami, and the later explosions that rocked the plant. Tomorrow technicians hope to connect cables to the No 3 and No 4 reactors.
The International Atomic Energy Authority director general, Yukiyo Amano, described the situation as "grave and serious" and described cooling the reactors as "extremely important".
"I think it is a race against time," he said.
If the attempt to attach cables fails, engineers may have to bury the facility in sand and concrete, similar to what happened in Chernobyl, in a last-ditch effort to end the crisis, the plant's operator, Tokyo Electric Power Company, said.
"It is not impossible to encase the reactors in concrete," said a Tepco official. "But our priority right now is to try and cool them down first."
Water cannons from six fire engines and a lorry were used earlier yesterday to send water into the stricken No 3 reactor, which is the focus of concern as it is the only one with a fuel mix that contains plutonium, which is more hazardous than uranium.
Efforts centre on maintaining water levels in the reactors' spent fuel pools to prevent material being exposed to the air, catching fire and releasing large amounts of radiation.
A total of 304 workers, operating in shifts, are trying to manage the stricken plant, although analysts said the masks, goggles and protective suits sealed by duct tape they were wearing offered only limited protection against the high levels of radiation. Reports yesterday said it was unclear if the workers were volunteers or had been ordered to remain.
Despite the international concern the Fukushima crisis has sparked, the dangers posed so far were limited, according to the World Health Organisation.
"At this point, there is still no evidence that there's been significant radiation spread beyond the immediate zone of the reactors themselves," Michael O'Leary, the organisation's China representative, said.
"At the same time, we know that the situation is evolving and we need to monitor closely and see what happens over time."
IAEA officials called on the Japanese authorities to provide more information on the situation at Fukushima, although the prime minister, Naoto Kan, insisted his government was disclosing everything it knew.
The Japanese nuclear authorities yesterday upgraded the crisis at three of the plant's reactors to a level five incident on a seven-point scale, although French officials have previously said it should be classified as level six. The 1979 Three Mile Island incident in the United States was level five, while the 1986 Chernobyl disaster was a seven.
Experts said because the situation had apparently not worsened for two days, they were hopeful the plant could be stabilised, as heat emitted by the nuclear material is reduced over time.
"As time goes by and things don't get substantially worse, we can be cautiously optimistic the situation will resolve itself without a catastrophe," Dr Neil Hyatt, a professor of nuclear chemistry at the University of Sheffield in the UK, told The National by telephone.
"After two to three weeks, the residual heat in the reactor will have decayed very substantially."
A minute's silence was held yesterday afternoon, a week on from the earthquake and tsunami that devastated much of north-east Japan. Rescue teams searching through debris were among those who lined up to take part in the tribute to the thousands who have died.
The death toll yesterday rose to 6,539, with a further 10,354 missing, although the final number is likely to be higher.
Evacuation centres, many still without power in the cold weather, house nearly 400,000, and the government yesterday said it was considering sending many people to regions not hit by the earthquake and tsunami. Almost 320,000 households are without power and 1.6 million lack running water.
Many homeless are likely to move to municipal housing, although thousands of prefabricated houses will also be built, Patrick Fuller, of the International Federation of Red Cross and Red Crescent Society, told Reuters.
Efforts to look after survivors are being hampered by a lack of water, food and fuel.
"We have enough medicine here in Sendai, mostly stored at drug wholesale companies, we just can't deliver them because we're running out of gasoline," Yukio Nagai, the chairman of the Sendai medical association, told Bloomberg.
Some hospitals in the city, which housed one million people and was badly hit by the tsunami, said they had so little food they were moving patients to evacuation centres.
While some criticised the government for the lack of supplies, the transport minister, Akihiro Ohata, told reporters in Tokyo fuel shortages were stopping supplies reaching the areas where they were needed. Damage to seaports has been blamed for hampering deliveries of fuel in some areas.
As foreigners continuing to fly out of Japan, the International Air Transport Association urged carriers to try to avoid refuelling in the country amid concern over shortages.