Hanford's B Reactor was named a National Historic Landmark on Monday, recognizing the role it played in shaping 50 years of U.S. and world history.

Not only will that designation help efforts to preserve the reactor as a museum, but the growing interest in the reactor has led the Department of Energy to increase public access to it.

Starting in March, the reactor will be open to the public at least three days a week and no advance registration will be required for "drive-up" visits, said Jeffrey Kupfer, the DOE acting deputy secretary, during a visit to the reactor Monday.

National Historic Landmark status is the highest historical recognition awarded by the United States to historic properties.

Just 3 percent of the sites on the National Historic Registry are elevated to landmark status, said Lynn Scarlett, the Department of Interior deputy secretary, as she stood in front of the towering face of the reactor core Monday.

"I think we can be assured (B Reactor) will be permanently protected and preserved," she said.

When properties are designated as landmarks, it attracts not only money and grants for preservation, but it also anchors the property in the public's mind as a place that deserves significant recognition, she said.

"Its construction was a phenomenal achievement," she said. "It is emblematic of the greatest generation."

The reactor, built in 13 months, was the world's first full-scale reactor, taking science that had advanced little beyond theory and producing plutonium in quantities large enough for the first atomic explosion in the New Mexico desert.

It then made plutonium for the atomic bomb dropped on Nagasaki, Japan, helping to end World War II.

When the Eastern Washington desert was picked in 1942 for the Manhattan Project site that would produce plutonium, "World War II was going badly for the Allies," said Michele Gerber, a Richland historian. "There was no assurance we were going to win the war."

In five months, 51,000 workers were brought to the desert to work a minimum of 50-hour weeks building B Reactor and a processing plant to separate plutonium from its irradiated fuel. With the reactor's startup, under the watchful eyes of physicist Enrico Fermi, it launched the Atomic Age.

"This machine changed the world," Gerber said. "It changed the balance of power for all the years since then. It changed science, energy, physics, medicine, environmental science, the way nations conduct peace and war and even the way we live our everyday lives."

B Reactor is only open a few days each year to the public and getting one of the limited seats on a bus tour that includes a stop at the reactor takes quick action. This year 2,000 seats available on tours to the reactor filled up within a few hours of the start of registration.

"We at the department are very committed to preserving the significance of the reactor and making it more accessible," Kupfer said. "We want to ensure as many people as possible have the opportunity to learn about this important period of history."

Under the new access program, "the next generation of Enrico Fermis can buckle up in the family car to come see it," Kupfer said.

He wants current and future engineers and scientists to see how workers pulled together to design and build the reactor. It is the inspiration the nation needs to solve issues such as providing a secure energy future, he said.

Families will be able to drive out to the Vernita Bridge area of western Hanford and then will board a shuttle bus for a short drive along the Columbia River through the secure area of the site to the reactor.

The reactor is expected to be open at least three days a week from March through October 2009. DOE still is working out details to allow children in the reactor complex. Now tours are limited to those who are at least 18.

DOE also is preparing to install a gate and temporary restroom facilities and to make minor road repairs to allow the increased access.

DOE still has a year or two to decide whether B Reactor will be permanently pulled from the Hanford cleanup program, which calls for tearing down Hanford's nine plutonium production reactors to their radioactive cores and then sealing them up to allow radiation to decay over the next 75 years.

Public areas of B Reactor pose no radiation risk to the public, say DOE officials.

Landmark status is an important step in saving the reactor, Kupfer said. DOE also wants to see continued local and state support for preserving the reactor, he said. It also will evaluate the costs of operating tours of the reactor, although that appears to be manageable, he said.

One of the next steps toward preserving the reactor is the completion of a National Park Service feasibility study on preserving Manhattan Project sites.

Most National Historic Landmarks do not become national parks, Scarlett said. But "park affiliation takes many forms," she said.

That includes the National Park Service not taking ownership of properties, but helping to provide interpretation of them.

"Our watchword is partnership," she said. "It is an unfolding story."

In 2007 the Hanford Reach Interpretive Center Board adopted a resolution committing the center "to operate tours of the B Reactor and fulfill our related coordination and management duties."

Four other Manhattan Project sites already have been named National Historic Landmarks. They include the Trinity Site, where B Reactor plutonium was used for the first atomic explosion, and the Chicago Pile I, where Fermi showed a self-sustaining nuclear chain reaction was possible. That led to the construction of B Reactor, which was 500 million times more powerful.

Sen. Patty Murray, D-Wash., a longtime supporter of saving the reactor, has included $500,000 to develop B Reactor into a museum and $200,000 to improve the road to the reactor in a 2009 Senate appropriations bill.

"The B reactor will be an important attraction for the region, and it will give visitors from across the country an opportunity to learn about and reflect on the contribution made by Hanford and the Tri-Cities during World War II and the Cold War," she said in a statement Monday.

The news of National Historic Landmark status for the reactor and increased access "is a big victory for the Tri-Cities," said Rep. Doc Hastings, R-Wash., who played a key role in pushing B Reactor through the long process needed for landmark designation.