Japanese officials have begun pumping seawater into a second nuclear reactor at the Fukushima No. 1 power plant 140 miles north of Tokyo to cool the reactor core in a last-ditch effort to stave off a core meltdown.
The action indicates that the reactor's normal backup cooling system has failed and is no longer able to supply fresh water to the core. Officials at Tokyo Electric Power Co., which owns the plant, have been struggling to keep six shut-down nuclear reactors cooled because seawater from the tsunami that followed Friday's magnitude 9.0 earthquake damaged the diesel generators that power the circulating pumps.
An explosion Saturday night at the No. 1 reactor destroyed the cooling system there and officials had little choice but to begin injecting seawater laced with boron directly into the reactor containment vessel. Seawater is highly corrosive, particularly when heated, and injecting it into the reactor means the company is, for all practical purposes, abandoning the reactor for all future uses.
That action at the No. 1 reactor seems to have been successful so far. Power company officials have reported that radiation levels at the plant have fallen and that the core seems to be cooling effectively.