YAKIMA, Wash. (AP) - The National Park Service's advisory board on Tuesday recommended designating the world's first full-scale nuclear reactor, which produced plutonium for one of two bombs dropped on Japan during World War II, as a national historic landmark.

The unanimous vote Tuesday brings former weapons workers and local residents one step closer to preserving the historic B Reactor at south-central Washington's Hanford nuclear reservation. A final decision on the reactor rests with Interior Secretary Dirk Kempthorne.

"This is a great step toward preserving both the B Reactor and an important chapter of our nation's history," Sen. Patty Murray, D-Wash., said in a statement announcing the decision. "The B Reactor will give future generations a chance to learn about the important contribution this region made to the World War II effort and the service and sacrifice of the Hanford community."

Built in just 13 months, B Reactor was the centerpiece of the federal government's top-secret effort to build the atomic bomb in the 1940s.

Construction began on June 7, 1943, six months after physicist Enrico Fermi turned the theory of nuclear power into the reality of the Atomic Age. In short order, the reactor produced plutonium for the first man-made nuclear blast, the Trinity test in New Mexico on July 16, 1945, and for the bomb that was dropped on Nagasaki, Japan, on Aug. 9, 1945.

The government shut down B Reactor in 1968 and decommissioned it.

Eight other reactors were built at Hanford to produce plutonium for the U.S. nuclear weapons arsenal. The remnants of that effort today make Hanford the nation's most contaminated nuclear site, with cleanup costs expected to top $50 billion.

Five reactors at the site already have been dismantled and cocooned, which involves removing extra buildings around the reactors, demolishing all but the shield walls surrounding the reactor cores and sealing them in concrete.

Under a cleanup schedule managed by the U.S. Department of Energy, dismantling of B Reactor could have begun as early as 2009. However, the department said it would maintain the reactor while the Park Service decided whether it should be preserved and made available for public access.

The U.S. Energy Department allows limited tours of B Reactor, with some areas blocked off for safety reasons. The department has not opposed preserving the reactor, but has said it must eventually be managed by another agency, such as the Park Service.

Hank Kosmata, president of the B Reactor Museum Association in Richland, cheered the decision, noting that the reactor already has been recognized as a landmark by several engineering groups.

"All those things make it more likely, I believe, that the Department of Energy will find a way to cooperate with the parks department and others to preserve it forever," he said. "That's our hope."

There are more than 2,300 national historic landmarks across the country. Other sites recommended for national-landmark status Tuesday include the old Coltsville factory complex in Hartford, Conn., where Colt revolvers and other weapons were made.