Working overnight into Sunday, engineers have successfully restored power to cooling pumps in two reactors at the disabled Fukushima Daiichi nuclear power plant, the first genuinely hopeful sign in the week-long battle to prevent a full-scale meltdown at any of the six reactors at the site.

Although power has so far been restored only at reactor buildings 5 and 6, which were not considered a particular threat, that success suggests that workers are finally beginning to make some headway in their effort to prevent more radiation from escaping the plant.

Photos: Unrelenting crisis grips Japan

The two reactors had been shut down at the time the magnitude 9 earthquake struck a week ago, but spent fuel rods in an upper level of the reactor buildings were still generating heat and required cooling. When electricity at the site was lost and the tsunami damaged backup generators, the pools holding the fuel rods began to grow warmer.


Officials of the Tokyo Electric Power Co., which owns the plant, said water in the no. 5 pool had already cooled by about 10 degrees Fahrenheit since the cooling pumps had started working.

Engineers said they hoped to have the power connected to the remaining reactor buildings sometime Sunday or early Monday.

Meanwhile, workers had jury-rigged an unmanned device that could spray seawater on the No. 3 reactor for up to seven hours at a time and they hoped to install similar devices at other buildings. Police and military were also spraying water manually on the other buildings at the site in an effort to keep the reactor cores and the spent fuel pools cooled and prevent a meltdown that would release large amounts of radiation into the environment.

The most recent reports suggest that the heavy spraying is working and has reduced radiation levels at the plant.


Engineers had run a power line to the Fukushima Daiichi plant, 150 miles north of Tokyo, from the country’s electrical grid Friday night, but connecting it to the buildings at the facility has been a bigger problem than anticipated. Workers have been able to spend only limited amounts of time in the facility to make the connections, and engineers have had to laboriously go through and check all the circuitry before power is turned on to ensure that a surge of current does not create more problems than it solves.

Officials of the company had said they hoped to get power restored to all of the six buildings at the facility by Sunday, but that estimate now seems overly optimistic. Engineers have been focusing their efforts on reactors No. 2 and 3 and the building housing reactor No. 4, which also houses a damaged spent fuel pool, but the need to build shelters to protect workers and equipment from the water that was being sprayed, as well as the radiation, delayed efforts.

Reactor No. 2 is thought to have a cracked containment vessel and is thus believed to be potentially the most problematic reactor. Reactor No. 3 is not known to be damaged, but its fuel rods contain a mixture of uranium and plutonium. Plutonium is highly carcinogenic in even very small quantities, and a leak of the material would be considered disastrous.

The pool at reactor No. 4 has the hottest spent fuel and is thought to have either holes in the walls of the pool or some other type of leak that is allowing water to run out. It is thus imperative to cool those heat sources first.


Even if electricity is restored, it is not clear how much benefit that will provide. It will certainly bring power to valves and controls in the reactor buildings, but most experts believe the cooling pumps in reactors No. 1, 2 and 3 were damaged, both by the hydrogen explosions that occurred in the first four days after the earthquake and by corrosion from the seawater and boron that have been pumped into the reactor.

Experts do not believe the cooling pumps at reactors No. 4, 5 and 6 had been damaged, and the success in restoring power at No. 5 and 6 suggests that assessment was correct. Many U.S. experts think that bringing power back online at Fukushima will mark a major turning point in the effort to bring the situation back under control.

The seawater that authorities are pumping into the plant is laced with boron, which serves to absorb neutrons released during the fissioning, or splitting, of uranium atoms, and thus serves to tamp down chain reactions and reduce heat production. But Japan is running short of the crucial element. South Korea and France said Friday that they would ship 150 tons of boron to Japan to assist in the battle.

Photos: Unrelenting crisis grips Japan


thomas.maugh@latimes.com