The Atomic Energy Act of 1946 (McMahon Act) determined how the United States would control and manage the nuclear technology it had jointly developed with its World War II allies, the United Kingdom and Canada. Most significantly, the Act ruled that nuclear weapon development and nuclear power management would be under civilian, rather than military control, and established the United States Atomic Energy Commission for this purpose.
It was sponsored by Senator Brien McMahon, a Democrat from Connecticut, who chaired the United States Senate Special Committee on Atomic Energy, and whose hearings in late 1945 and early 1946 led to the fine tuning and passing of the Act. The Senate passed the Act unanimously through voice vote, and it passed the House of Representatives 265–79. Signed into law by President Harry S. Truman on August 1, 1946, it went into effect on January 1, 1947, and the Atomic Energy Commission assumed responsibility for nuclear energy from the wartime Manhattan Project.
The Act was subsequently amended to promote private development of nuclear energy under the Eisenhower administration's Atoms for Peace program in 1954. In restricting the access to nuclear information to other countries, it created a rift between the United States and its allies, particularly Britain and Canada, which had participated in the Manhattan Project. This resulted in cumbersome command and control arrangements, and in Britain developing its own nuclear weapons. The Act was amended in 1958 to allow the United States to share information with its close allies.
Origins
Nuclear weapons were developed during World War II by the wartime Manhattan Project. Key scientists working on the project anticipated that their development would have wide-ranging implications. However the project director, Major General Leslie R. Groves Jr., was reluctant to spend project funds on activities beyond those required to win the war. Nonetheless, Arthur Compton of the Metallurgical Project in Chicago commissioned a report on post-war nuclear energy, and the Military Policy Committee, the Manhattan Project's governing body, commissioned a similar study by Richard Tolman. Both reports called for a comprehensive, government-supported nuclear energy program, with military, scientific, and industrial aspects.
In July 1944, Vannevar Bush, James B. Conant and Irvin Stewart produced a proposal for domestic legislation to control nuclear energy. Conant submitted this to the Secretary of War Henry L. Stimson in September 1944, and then to the Interim Committee, a body created by President Harry S. Truman in May 1945 to supervise, regulate and control nuclear energy until such a time as Congress created a permanent body to do so. In June 1945, the Interim Committee asked George L. Harrison, an assistant to Stimson and a member of the committee, to prepare legislation.
Creation of the Act
May–Johnson Bill
Harrison brought in two experienced Harvard Law School-educated War Department lawyers, Brigadier General Kenneth Royall and William L. Marbury Jr., to take up the job of drafting the legislation. The legislation was based on Bush and Conant's proposal, and the organization that it proposed was based on the existing structure of the Manhattan Project. Their draft bill would have created a nine-person commission consisting of five civilian and four military members. It granted the commission broad powers to acquire property, operate facilities, conduct research, regulate all forms of nuclear energy, and administer its own security, administrative and audit regimes.