Engineers believe that Tank 6 leaked from two small cracks near the top of the vessel, said Dean Campbell, a spokesman for Westinghouse Savannah River Co. Westinghouse operates SRS for the Department of Energy.

To prevent the tank from leaking again, engineers will pump about 40,000 gallons of waste to another tank, lowering the level in Tank 6 below the two cracks, Mr. Campbell said. The tank, which has maximum capacity of 750,000 gallons, now holds about 662,000 gallons, he said.

Site workers discovered that the tank had leaked Jan. 12, when they found about 90 gallons of waste puddled in a saucerlike steel vessel beneath the tank.

The waste was made up of water containing a small amount of tritium, Mr. Campbell said. Tritium is a radioactive gas used in nuclear weapons.

The waste did not reach the soil or ground water, SRS officials said.

During an inspection, engineers discovered four other leaks in the tank, but those have stopped seeping and are not believed to have contributed to the puddle of waste beneath the vessel, Mr. Campbell said.

Engineers used a ventilation system to dry much of the puddle, but an unknown amount of liquid remains, Mr. Campbell said.

The site has 51 radioactive-waste tanks, two of which are no longer used. Nine of the tanks have developed leaks over the years, Mr. Campbell said. In 1960, one leak, of less than 100 gallons, leached into the soil, he said.

Reach Brandon Haddock at (706) 823-3409.