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Students arrive at B Reactor for a tour. The Department of Energy works with elementary, middle, and high schools around the region to highlight B Reactor’s role in ushering in the atomic age, and the importance of STEM education.
Students arrive at B Reactor for a tour. The Department of Energy works with elementary, middle, and high schools around the region to highlight B Reactor’s role in ushering in the atomic age, and the importance of STEM education.

On July 16, 1945, the research and development efforts of the nation’s once-secret Manhattan Project were realized with the detonation of the world’s first nuclear device at the code-named “Trinity” test site over 200 miles south of Los Alamos, New Mexico.

This first-ever detonation of a nuclear device thrust mankind into a new era marked by the development of weapons with previously unimaginable power, and a complicated legacy that includes the fields of nuclear medicine and nuclear energy, the growth of a vital national laboratory system, and the vast environmental cleanup responsibilities entrusted to the Office of Environmental Management (EM). 

Today, EM continues cleanup activities from the impacts of national security efforts in World War II across the remaining Manhattan Project sites and those involved in the Cold War. EM’s charge also includes support for the preservation and recognition of some of the historic facilities of the Manhattan Project.

B Reactor Atomic Bomb Plant
B Reactor at the Hanford Site

The B Reactor at DOE’s Hanford Site in Washington state was constructed in 1943 and produced plutonium used in the Trinity Test, as well as for the atomic bomb dropped on Nagasaki, Japan. Now one of five Hanford facilities in the Manhattan Project National Historical Park, B Reactor, has had visitors from all 50 states and more than 90 countries worldwide.

Los Alamos National Laboratory (LANL) was established for a single purpose: to design and build an atomic bomb. EM Los Alamos Field Office, established in 2015, pursues an active legacy cleanup mission.
Los Alamos National Laboratory

Los Alamos National Laboratory (LANL), was established for a single purpose: to design and build an atomic bomb.  EM Los Alamos Field Office, established in 2015, pursues an active legacy cleanup mission. It investigates hazardous chemical and radioactive materials contamination as a result of past LANL operations and remediates sites where such materials are found above acceptable regulatory levels.

Today, the Graphite Reactor is part of the Manhattan Project National Historical Park. Public tours take visitors to one of the world’s most important pioneering nuclear research facilities.
Graphite Reactor at the Oak Ridge Site

The Graphite Reactor at the Oak Ridge Site once produced the world’s first few grams of plutonium, created the first sparks of nuclear-generated electricity and went on to serve as one of the most prestigious nuclear research facilities in the world. Today, the Graphite Reactor serves as one of the Manhattan Project National Historic Park’s most popular attractions in Oak Ridge.

K-25 Building Site now known as the East Tennessee Technology Park
K-25 Building Site now known as the East Tennessee Technology Park

The K-25 building produced uranium for the world’s first nuclear weapons. The K-25 site, now known as the East Tennessee Technology Park, has been transformed by the EM program. More than 500 facilities have been demolished and much of the land has been transferred to the community for economic development, conservation, and historic preservation including the K-25 History Center that opened in 2020.

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As U.S. Marks Trinity Test’s 75th Anniversary, EM Continues Progress at Manhattan Project Sites
On July 16, 1945, the world's first nuclear explosion occurred more than 200 miles south of Los Alamos in Alamogordo, New Mexico.
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The History of a Park Dedicated to the Manhattan Project Story
The Manhattan Project was an unprecedented, top-secret research and development program created during World War II to develop an atomic weapon.
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B Reactor: Preserving a Transformative Piece of U.S. History
The atomic age began in the New Mexico desert on July 16, 1945, with the Trinity Test — the culmination of the top-secret Manhattan Project.
Learn More