The Energy Department announced yesterday that it will not restart its main plutonium-producing reactor at the Hanford Nuclear Reservation in Washington state, saying other sources can meet the military's plutonium requirements.

The Hanford reactor, called the N reactor, was shut down more than a year ago after a special review commission concluded that it needed extensive safety modifications.

The Energy Department has since spent more than $50 million in repairs on the 25-year-old reactor, but efforts to restart it have been opposed by Northwest officials and environmental groups who contend that it still represents a major safety hazard.

In a statement, DOE said it expects to meet plutonium requirements through its reactors at the Savannah River Plant in South Carolina, one of which produces plutonium, and by recycling "retired nuclear weapons and residue material."

According to Hanford officials, the action will cost the Richland, Wash., area about 2,600 jobs over the next two years and could eventually put nearly half of Hanford's 14,000 employees out of work.

DOE spokesman Ken Morgan said that about 3,300 people are employed at the N reactor but that the shutdown "eventually will impact other activities because the N reactor is at the head of the plutonium production system."

More than 3,000 additional employees work in various extraction and finishing plants that turn the reactor's irradiated fuel rods into plutonium for nuclear weapons.

The auxiliary plants have been processing stockpiled fuel rods and other materials during the N reactor's shutdown.

The N reactor, completed in 1963, is the last of nine that once dotted the 475-square-mile reservation in eastern Washington. The aging reactor came under fire in 1986 after the nuclear accident at Chernobyl in the Soviet Union because of its similar design.

"We have always maintained that the reactor was safe," Morgan said. "The work that was done here was good work, and the reactor is good."

However, DOE officials have acknowledged that the reactor's days were numbered because of deformations in its graphite core that were expected to force it out of operation by the early 1990s.

"This decision confirms what many of us have been saying for some time," Sen. Brock Adams (D-Wash.) said. "The continued operation of the N reactor is not necessary for our national security, nor would it have been safe to restart the N reactor without extensive repairs."

DOE said it intends to complete scheduled repairs to preserve the option of restarting the plant if plutonium requirements increase and new production facilities are not available.