An unprecedented attempt to douse an apparently overheating spent fuel pool with tons of coolant water at a stricken nuclear plant in Fukushima bore some fruit Thursday, but the emission of smoke newly confirmed at another pool suggests the difficulties that lie in the way of resolving the crisis triggered by the March 11 quake and tsunami.

Up to 64 tons of water were aimed by helicopters and fire trucks of the Self-Defense Forces as well as a water cannon truck of the Metropolitan Police Department into the pool at the No. 3 unit of Tokyo Electric Power Co.'s Fukushima Daiichi plant.

The utility said vapor rising from the partially destroyed No. 3 reactor building suggests the operation went some way toward cooling down the pool that could otherwise emit highly contaminated radioactive materials.