Safety problems that halted production of U.S. nuclear weapons materials expose a "bad trend" and a "sense of complacency" in the operations of nuclear plants, top Energy Department officials said Wednesday.

"The risks we are facing are serious," said Richard Starostecki, deputy assistant energy secretary for safety, health and quality assurance.Energy Secretary John S. Herrington said Tuesday that the government will not be able to manufacture nuclear weapons materials for 21/2 months because of safety problems, but he said that raises no threat to national security.

The department had planned to restart one of its three nuclear weapons reactors at its Savannah River Plant in South Carolina as early as next month but now does not expect the first of them to reach full operation until January, Herrington said.

Starostecki, interviewed on "CBS This Morning," said the nation's aging nuclear weapons manufacturing plants must remain in operation for another 10 to 15 years while they are being replaced. The Savannah River reactors began operations in 1954.

"These are the only supplies we have for our national security," said Starostecki. "We're trying to take measures now before the situation does degrade and we have a serious accident."

Referring to the shutdown last weekend of the main plutonium processing plant at Rocky Flats in Golden, Colo., because of a radioactive contamination incident, he said, "The incident of the workers is indicative of a bad trend and we want to stop it before it does result in any off-site release" of radioactive material.

The top Energy Department spokesman, C. An-son Franklin, said on NBC-TV's "Today" that some contractors and department managers have become so accustomed to the old equipment that "they don't stop long enough to see what was the cause" of minor problems.