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Projects & Facilities

B Reactor

Background and History
The B Reactor National Historic Landmark at the Hanford Site in southeastern Washington state was the world’s first full-scale plutonium production reactor. Created as part of the top-secret Manhattan Project during World War II, B Reactor produced plutonium used in the Trinity Test, and in the atomic bomb dropped on Nagasaki, Japan to end World War II. The reactor was designed and built by the DuPont company based on experimental designs tested by Dr. Enrico Fermi at the University of Chicago and tests from the X-10 Graphite Reactor at Oak Ridge, Tennessee. 
Construction of B Reactor began in October 1943. Fuel was loaded into the reactor on Sept. 13, 1944, and it reached full power in February 1945. 
Its mission thought complete, B Reactor was initially shut down at the end of 1946. However, amid growing tension between the U.S. and former Soviet Union, B Reactor was restarted in 1948 to support production of plutonium for the Cold War until 1967. At the direction of the U.S. Atomic Energy Commission, the B Reactor was shut down on Feb. 12, 1968.
Path to Preservation
More than 30 buildings and 20 service facilities were part of B Reactor operations. From 1969 through 2006 all were dismantled and removed except for the reactor building, main exhaust stack and river pump house, which still pumps water used for modern site activities. As recently as 2008, plans called for the B Reactor and its exhaust stack to be dismantled as part of Hanford cleanup.
The B Reactor was named a National Historic Mechanical Engineering Landmark by the American Society of Mechanical Engineers in 1976, was listed in the National Register of Historic Places in 1992, was designated a National Historic Civil Engineering Landmark in 1994, and became a National Historic Landmark in 2008. At the ceremony conferring historic landmark status on the facility, the acting deputy secretary of the U.S. Department of Energy (DOE) stood with the deputy secretary of the U.S. Department of the Interior and announced a policy change for B Reactor: its new path would be preservation and public access.
DOE began to make access and safety improvements to the reactor in 2008 to support public visits. DOE hosted its first public tours of B Reactor in early 2009 and by 2012 was hosting about 10,000 visitors to B Reactor each year. Today, DOE is well on its way to universal access to B Reactor for all interested guests, having lowered the age requirement for visitors from 18 to 12 and dropped the requirement that visitors be U.S. citizens.
The B Reactor has always had strong support from a variety of local constituent organizations. The B Reactor Museum Association, for example, was established in 1990 with the goal of saving the B Reactor from demolition. In the early 1990s, that grass roots support grew to include many local and state officials, the Tri-City Development Council, Visit Tri-Cities, and members of the Washington state congressional delegation. In 2004 Congress directed the National Park Service (NPS) to undertake a special resource study to determine whether it was appropriate and feasible for the NPS to create a new unit of the park system devoted to telling the Manhattan Project story. The study ultimately answered in the affirmative and recommended park locations at each of the three original Manhattan Project sites: Hanford; Oak Ridge, Tennessee; and Los Alamos, New Mexico.
In December 2014, then U.S. Rep. Doc Hastings, with support from Washington’s U.S. Sens. Maria Cantwell and Patty Murray, obtained congressional authorization for the new Manhattan Project National Historical Park. President Barack Obama signed the bill into law on Dec. 19, 2014. DOE and NPS signed a memorandum of agreement (MOA) for joint management of the new park on November 10, 2015. Consistent with the legislation, DOE owns and operates its historic facilities and provides public access to the park. The NPS is responsible for interpreting the Manhattan Project story for the public and providing visitor services at the three park locations.
The U.S. Department of Energy offers public tours of the B Reactor. Visit the Hanford Site Tours webpage for more information.

BReactorControlWEBThere were no moving parts inside the B Reactor, and the only sound that could be heard during the reactor’s operation was the flow of millions of gallons of Columbia River water rushing through the reactor to cool it. The reactor also didn’t need many people to operate it, so a typical crew numbered less than 20 people.

Last Updated 09/08/2023 7:51 AM