Plutonium production will not resume at the Hanford nuclear complex because the government has enough bomb-grade material stockpiled, Energy Secretary James Watkins says.

He made the announcement this week in Portland, Ore., before a two-day tour of the 560-square-mile complex.The PUREX plant - for plutonium-uranium extraction - was built in the 1950s to extract plutonium from uranium and process it for weapons. It was shut down in 1988 because of safety violations and had been scheduled to reopen in the spring.

The closing will leave the government without an active extraction plant, although similar plants elsewhere in the country could be activated if necessary, the department said.

The plant will be placed on standby for at least two years while the government studies possible future uses, Watkins said. It might be used to prepare fuel for long-term storage, he said.

Earlier this year a study by the General Accounting Office, the investigative arm of Congress, said there was no evidence the plant was needed, given the nation's plutonium stockpile and a reduction in the nation's arsenal.

Environmentalists opposed a reopening because of past safety violations and concerns over storage of nuclear waste at the site. Hanford is the Energy Department's most polluted nuclear production site.

A report released by the GAO last week concluded that ferrocyanide and hydrogen gas buildup in some of the plant's 177 storage tanks could cause an explosion that would expose nearby residents to dangerous amounts of radiation.

Hydrogen has developed naturally in 20 tanks. Ferrocyanide was added to 22 other tanks in the 1950s to help separate liquids from solids. The liquids were pumped out to increase tank capacity.

Also, Energy Department documents indicate some of the tanks may have leaked as much as 1 million gallons of radioactive water into the soil.

Rep. Mike Synar, D-Okla., chairman of the House Government Operations subcommittee on environment, energy and natural resources, has estimated that closing the plant permanently would save the government $750 million over 15 years.

The plant's 600 workers will stay on to maintain the plant while the government decides its destiny.