Atomic Energy Act of 1946 The Atomic Energy Act of 1946 ( McMahon Act ) determined how the United States federal government would control and manage the nuclear technology it had jointly developed with its wartime allies ( Britain and Canada ) . Most significantly , the Act ruled that nuclear weapon development and nuclear power management would be under civilian , rather than military control , and it 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 . It passed the House of Representatives 265 – 79 . Signed into law by President Harry Truman on August 1 , 1946 , it went into effect on January 1 , 1947 . Origins . Nuclear weapon s 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 use spend project ' s 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 . May - Johnson Bill . Harrison brought in two experienced Harvard Law School - educated War Department lawyers , Brigadier General Kenneth Royall and William L . Marbury 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 - man commission consisting of five civilian and four military members . It granted the commission broad powers to acquire property , to operate facilities , to conduct research and to regulate all forms of nuclear energy . It could acquire property , and administer its own security , administrative and audit regimes . Royall and Marbury envisaged nuclear energy being controlled by experts , with a minimum of political interference . The commissioners would be appointed for indefinite terms , and the President ' s power to remove them would be limited . They would be supported by four advisory boards , for military applications , industrial uses , research , and medicine , the membership of which would be restricted to those with technical qualifications . Day to day running of the organization would be in the hands of an administrator and his deputy . The Royall - Marbury bill was reviewed by the Interim Committee at its July 19 meeting and revised in line with their suggestions . After the Atomic bombing of Hiroshima and Nagasaki lifted the veil of secrecy surrounding the Manhattan Project , Royall and Marbury were able to consult with the Attorney General , the Judge Advocate General , and the Office of Scientific Research and Development . The draft was sent to the President in August for circulation among , and comment from , affected government agencies . Only the State Department had objections , on the basis that it was still involved in trying to hammer out an international agreement on nuclear energy . On October 3 , 1945 , the bill was introduced in the House of Representatives by Congressman Andrew J . May from Kentucky , the chairman of the House Military Affairs Committee , and into the Senate by Senator Edwin C . Johnson from Colorado , the ranking member of the Senate Military Affairs Committee . The bill was known as the May - Johnson Bill for its sponsors . May immediately had the bill referred to the Military Affairs Committee , which held hearings on October 9 . Bush , Conant and Groves all testified before the committee . But in the Senate Military Affairs Committee , the bill was held up by Senator Arthur H . Vandenberg . There was a storm of criticism from scientists , particularly those at the Metallurgical Laboratory in Chicago . Leo Szilard and Harold Urey were particularly notable critics . The bill created a powerful administrator and deputy administrator , and specifically stated that they might be members of the armed forces . It was feared that they would dominate the part - time commissioners . The fact that the bill emphasised that the administrator had to keep the deputy fully informed further aroused suspicion that administrator would be an Army officer and the deputy a Navy officer . The secrecy provisions also frightened many scientists . It contained severe penalties of up to ten years imprisonment and $ 10 , 000 in fines for security breaches . The " Chicago Sun " headline accused the War Department of attempting to railroad the legislation through Congress . Legislators found themselves in an unusual and uncomfortable situation . Nuclear weapons were terrifying , and the nature of nuclear energy was not widely understood . Because it was so new , there were no policies or precedents to guide the legislators , and traditional party alignments were absent . The scientists who had developed the new technology had never been vocal before , but suddenly were now . The victorious conclusion of World War II gave the armed forces enormous prestige , but there still remained the long - standing American distrust of standing armies , and the tradition of civilian control of the military . MacMahon Bill . On December 20 , 1945 , Senator Brien McMahon introduced an alternative bill on atomic energy , drafted by the Senate Military affairs Committee , which quickly became known as the McMahon bill . This was initially a very liberal bill towards the control of scientific research , and was broadly supported by scientists . McMahon framed the controversy as a question of military versus civilian control of atomic energy , although the May - Johnson bill also provided for civilian control . The McMahon bill attempted to address the controversial aspects of the May - Johnson Bill . The number of commissioners was reduced to five , who would serve full - time . No exemption was provided for serving military officers . An amendment caused them to have staggered terms of five years . While the bill was being debated , the news broke on February 16 , 1946 , of the defection of Igor Gouzenko in Canada , and the subsequent arrest of 22 people . The members of Congress debating the bill feared that " atomic secrets " were being systematically stolen by Soviet atomic spies . McMahon convened an executive session at which Federal Bureau of Investigation Director J . Edgar Hoover , Secretary of State James F . Byrnes and Groves were called to appear . Groves revealed that the British physicist Alan Nunn May had passed information about the Manhattan Project to Soviet agents . The more conservative elements in Congress now moved to toughen the act . Section 10 , which was formerly titled " Dissemination of Information " , now became " Control of Information " . This new section contained the novel doctrine later described as " born secret " or " classified at birth . " It defined a new legal term , " restricted data " , as " all data concerning the manufacture or utilization of atomic weapons , the production of fissionable material , or the use of fissionable material in the production of power , " unless the information has been declassified . The phrase " all data " included every suggestion , speculation , scenario , or rumor — past , present , or future , regardless of its source , or even of its accuracy — unless it was specifically declassified . This restriction on free speech , covering an entire subject matter is still enforced . The " wall of secrecy " set up by the Act confined research and development within the country and government . Representative Helen Gahagan Douglas , who sponsored the McMahon bill in the House , vigorously defended the section against counterarguments . She dismissed objections that it would " give away the secret of the bomb " , asserting that America ' s advantage in nuclear weapons could only be temporary , whereas the bill could perpetuate its lead in scientific research . An important addition , known as the Vandenberg Amendment , created a Military Liaison Committee to advise the commission on defense matters . Section 2 of the Act also created a General Advisory Committee , and a new Joint Committee on Atomic Energy to oversee the new organization . The Senate passed the Act unanimously through voice vote on June 1 , 1946 . Considerable political maneuvering was required before it was passed by the House 265 – 79 on July 20 . A compromise bill was then agreed to by both houses on July 26 . Truman signed the compromise bill into law as the Atomic Energy Act of 1946 on August 1 , 1946 . When it went into effect at midnight on January 1 , 1947 . the newly created Atomic Energy Commission assumed responsibility for nuclear energy from the wartime Manhattan Project . Private production of Nuclear Energy . An important omission from the Atomic Energy of 1946 was any mention of non - governmental use of nuclear energy , since military applications overshadowed all others at the time . The restrictions of the act related to secrecy , the control of fissile materials , the ownership of patents and the operation of production facilities placed a number of legal roadblocks in the way of private nuclear power stations . This was at odds with the Eisenhower administration ' s Atoms for Peace program , so in 1953 the Atomic Energy Commission presented a set of draft amendments to the Joint Committee on Atomic Energy for consideration . At some debate , this resulted in the Atomic Energy Act of 1954 . International relations . Implementing the McMahon Act created a substantial rift between United States and Britain . The new control of " restricted data " excluded the United States ' allies from receiving any information , although the British and Canadian governments , before contributing technology and manpower to the Manhattan Project , had made agreements with the United States about the post - war sharing of nuclear technology . Those agreements were formalized in the 1943 Quebec Agreement . In the case of the United Kingdom , these were developed further in the 1944 Hyde Park Agreement , which was signed by Winston Churchill and Franklin Roosevelt . The Hyde Park Agreement was lost in Roosevelt ' s papers after his death , and until the American copy of the document was found American officials were puzzled when the British mentioned it . The Quebec Agreement was an executive agreement that only applied to the Roosevelt administration , and the Senate had not seen the document . McMahon told Churchill in 1952 that " If we had seen this Agreement , there would have been no McMahon Act . " The McMahon Act fueled resentment from British scientists , and Churchill , and led to Britain developing its own nuclear weapons . Lewis Strauss , the Chairman of the Atomic Energy Commission , proposed in January 1958 that the President should be able to share nuclear information with allies that were making " substantial and material contributions to the national defense and security " . In addition to its own nuclear weapons , Britain had hosted American Strategic Air Command nuclear bombers since 1948 . Congress modified the McMahon Act in mid - 1958 , and America and Britain again began sharing nuclear research under the 1958 US – UK Mutual Defence Agreement . The stipulations contained in the Act caused significant controversy during debates over NATO ' s military command structure . Both Striking Fleet Atlantic and the United States Sixth Fleet have never been allowed to be placed anywhere but directly under American commanding officers — the Supreme Allied Commander Atlantic and Commander - in - Chief , Allied Forces Southern Europe , because the dominant legal interpretation of the McMahon Act has been that nuclear striking forces cannot be controlled by non - US commanders . This was the reason for the formation of Striking Fleet Atlantic as an independent entity , instead of being operationally subordinated to the UK Admiral serving as Commander - in - Chief , Eastern Atlantic , in October – November 1952 . This was also the reason why the Sixth Fleet , in its NATO guise as Naval Striking and Support Force , South , was placed under American control rather than Allied Forces Mediterranean when the European commands were agreed at the same time .