Efforts to fix problems that stopped production at the only U.S. facility able to produce nuclear weapons material intensified Monday with the addition of extra control room shifts at the Savannah River plant.

Federal officials also are expanding their on-site control as part of a sweeping safety drive that makes it unlikely the plant will meet a Dec. 31 goal for resuming production.Creating an extra, fifth shift for each of the plant's three reactors means that one of the 14-member control-room teams will be undergoing training at any given time.

The crews will double the time they spend each year on a computer simulator, up to 150 hours, and classroom work will be expanded as well, said Charlie Ahfield, a Du Pont reactor program manager.

Putting federal officials permanently inside each reactor facility, for the first time, will allow the government to keep a closer eye on their operation, which has been run since 1950 under contract by the E.I. du Pont de Nemours Co.