# Restricted Data

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Legal category of US nuclear secrets

A 1946 "Restricted Data" stamp on an [Atomic Energy Commission](/source/United_States_Atomic_Energy_Commission) document

**Restricted Data** (**RD**) is a category of [classified information in the United States](/source/Classified_information_in_the_United_States) that is defined by the [Atomic Energy Act of 1954](/source/Atomic_Energy_Act_of_1954) as:

all data concerning (1) design, manufacture, or utilization of [atomic weapons](/source/Nuclear_weapons); (2) the production of [special nuclear material](/source/Special_nuclear_material); or (3) the use of special nuclear material in the production of energy, but shall not include data declassified or removed from the Restricted Data category pursuant to section 142 [of the Act].[1]

The fact that its legal definition includes "all data" except that already specifically declassified has been interpreted to mean that atomic energy information in the United States is [born classified](/source/Born_classified), even if it was not created by any agency of the U.S. government.[2] The authority of the [United States Department of Energy](/source/United_States_Department_of_Energy) (DOE) to implement this authority as a form of [prior restraint](/source/Prior_restraint) was only once tested in court, with inconclusive results.[3][4]

"Restricted Data" should not be confused with the classification category of "[Restricted](/source/Classified_information#Restricted)", a relatively low category of classification. "Restricted Data" is not a level of classification; rather, a document can be classified as [Confidential](/source/Classified_information#Confidential), [Secret](/source/Classified_information#Secret), or [Top Secret](/source/Top_Secret), while also containing "Restricted Data." In addition, a document containing Restricted Data could also contain [Critical Nuclear Weapon Design Information](/source/Critical_Nuclear_Weapon_Design_Information) (CNWDI). In this way, a document, for instance, could be classified as "Secret" (S), "Secret//Restricted Data" (S//RD), or "Secret//Restricted Data-Critical Nuclear Weapon Design Information" (S//RD-CNWDI) depending on the type of information a document contains.

Access to Restricted Data requires an [L clearance](/source/L_clearance) or a [Q clearance](/source/Q_clearance) from the Department of Energy.

## History

The concept was initially introduced, with similar wording, in the [Atomic Energy Act of 1946](/source/Atomic_Energy_Act_of_1946). It was added at a relatively late moment to the bill by its creators, after the [Gouzenko affair](/source/Igor_Gouzenko) was leaked to the press and caused a fear of loss of "the secret" of the atomic bomb, as well as fears that the [Espionage Act of 1917](/source/Espionage_Act_of_1917) was not sufficiently adequate.[5]

The Atomic Energy Act of 1946 further specified that anyone who:

- communicates, transmits, or discloses... any document, writing, sketch, photograph, plan, model, instrument, appliance, note, or information involving or incorporating restricted data... to any individual or person, or attempts or conspires to any of the foregoing, with intent to injure the United States or with intent to secure an advantage to any foreign nation, upon conviction thereof, shall be punished by [death](/source/Capital_punishment) or [imprisonment for life](/source/Life_imprisonment)... or, by a fine of not more than $20,000 or imprisonment for not more than twenty years, or both...[1]

The act empowered and required the then-newly-created [Atomic Energy Commission](/source/United_States_Atomic_Energy_Commission) to regulate Restricted Data both internally and externally.

The Atomic Energy Act did not give the Atomic Energy Commission the authority to declare that a piece of information was or was not Restricted Data. Rather, it defines certain categories of information as inherently being Restricted Data, and thus "[born secret](/source/Born_secret)". The Atomic Energy Commission thus determines that documents *contain* Restricted Data, and they are authorized to *remove* specific facts from the category of Restricted Data, but they are not authorized to fundamentally *increase* the scope of the definition of Restricted Data. This was intentional, as Senator [Brien McMahon](/source/Brien_McMahon) explained at the time the bill was proposed, as it was intended to allay fears that the federal government could endlessly and arbitrarily expand the definition of what was secret beyond what was dictated by Congress: "The Commission's withdrawal power can only reduce — it cannot enlarge — the scope of the crime."[6]

The Atomic Energy Act revisions of 1954 effected some minor changes to the original 1946 definition, adding "design" as an explicit category of control, and changing the "fissionable materials" of the original definition into "special nuclear materials," which could include [thermonuclear](/source/Thermonuclear) fuels. Despite many years of debates about whether the Restricted Data category was too broad, or whether the "born secret" interpretation of it was prohibitive to peaceful industrial development or even unconstitutional, it was not otherwise fundamentally changed. [7]

In 1969, Congress removed capital punishment as one of the specific penalties imposed by the Atomic Energy Act.[8]

## Categories of Restricted Data

Section 142 of the Atomic Energy Act (42 U.S.C. 2162) allows certain nuclear weapons information to be removed from the Restricted Data category to be handled by the [Department of Defense](/source/United_States_Department_of_Defense) or the [Intelligence Community](/source/United_States_Intelligence_Community).[9]

- **Formerly Restricted Data** (**FRD**) is jointly determined by DoD and DOE to relate primarily to the military use of nuclear weapons, and is safeguarded as defense information (e.g., weapon yield, deployment locations, weapons safety and storage, and stockpile quantities).

- **Transclassified Foreign Nuclear Information** (**TFNI**) is information from any intelligence source that concerns the nuclear programs of foreign governments that was removed from the RD category by past joint agreements between DOE and the [Director of Central Intelligence](/source/Director_of_Central_Intelligence), or past and future agreements with the [Director of National Intelligence](/source/Director_of_National_Intelligence).

**Critical Nuclear Weapon Design Information** (**CNWDI**) is a category of RD provided to the DoD that reveals the theory of operation or design of components of a thermonuclear or implosion-type fission bomb, warhead, demolition munition, or test device. It is classified as either Secret (S//RD) or Top Secret (TS//RD).[9]

The **Sigma** categories are subject areas of RD nuclear weapons data related to nuclear weapons, components, or explosive devices or materials that have been determined to require additional protection. The current Sigma categories are Sigma 14, Sigma 15, Sigma 16 and Sigma 20.[10]

## See also

- [Critical Nuclear Weapon Design Information](/source/Critical_Nuclear_Weapon_Design_Information)

- [L clearance](/source/L_clearance)

- [Q clearance](/source/Q_clearance)

## References

1. ^ [***a***](#cite_ref-AEA_1-0) [***b***](#cite_ref-AEA_1-1) [Atomic Energy Act of 1954](https://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr0980/ml022200075-vol1.pdf#pagemode=bookmarks&page=14), Chapter 2, Section 11(y).

1. **[^](#cite_ref-2)** This interpretation does not seem to have been foreseen by the creators of the concept, however. See Alex Wellerstein (2021). *Restricted data: The history of nuclear secrecy in the United States*. Chicago: University of Chicago Press. [ISBN](/source/ISBN_(identifier)) [978-0-226-02038-9](https://en.wikipedia.org/wiki/Special:BookSources/978-0-226-02038-9)., page 455, footnote 70.

1. **[^](#cite_ref-3)** See *[United States v. The Progressive](/source/United_States_v._The_Progressive)* (1979).

1. **[^](#cite_ref-devolpi_4-0)** Alexander De Volpi; Jerry Marsh; Ted Postol & George Stanford (1981). *Born secret: the H-bomb, the Progressive case and national security*. New York: Pergamon Press. [ISBN](/source/ISBN_(identifier)) [0-08-025995-2](https://en.wikipedia.org/wiki/Special:BookSources/0-08-025995-2).

1. **[^](#cite_ref-5)** Alex Wellerstein (2021). *Restricted data: The history of nuclear secrecy in the United States*. Chicago: University of Chicago Press. [ISBN](/source/ISBN_(identifier)) [978-0-226-02038-9](https://en.wikipedia.org/wiki/Special:BookSources/978-0-226-02038-9)., 145–158.

1. **[^](#cite_ref-6)** Alex Wellerstein (2021). *Restricted data: The history of nuclear secrecy in the United States*. Chicago: University of Chicago Press. [ISBN](/source/ISBN_(identifier)) [978-0-226-02038-9](https://en.wikipedia.org/wiki/Special:BookSources/978-0-226-02038-9)., 156.

1. **[^](#cite_ref-7)** Alex Wellerstein (2021). *Restricted data: The history of nuclear secrecy in the United States*. Chicago: University of Chicago Press. [ISBN](/source/ISBN_(identifier)) [978-0-226-02038-9](https://en.wikipedia.org/wiki/Special:BookSources/978-0-226-02038-9)., 276.

1. **[^](#cite_ref-8)** Public Law 91-161, section 3(a), 83 Stat. 444 (24 December 1969).

1. ^ [***a***](#cite_ref-NMH2020_9-0) [***b***](#cite_ref-NMH2020_9-1) [Department of Defense](/source/United_States_Department_of_Defense) (2020). [*2020 Nuclear Matters Handbook*](https://www.acq.osd.mil/ncbdp/nm/NMHB2020rev/docs/NMHB2020rev.pdf) (PDF). Retrieved April 27, 2025.

1. **[^](#cite_ref-10)** [Department of Energy](/source/United_States_Department_of_Energy) (July 21, 2011). [*DOE Order 452.8, Control of Nuclear Weapon Data*](https://www.directives.doe.gov/directives-documents/400-series/0452.8-BOrder/@@images/file). Retrieved April 27, 2025.

v t e Dwight D. Eisenhower 34th President of the United States (1953–1961) Supreme Allied Commander Europe (1951–1952) Chief of Staff of the Army (1945–1948) Commander, Supreme Headquarters Allied Expeditionary Force (1943–1945) Military career Military career 1919 Motor Transport Corps convoy Louisiana Maneuvers Operation Torch European Theater of Operations Allied invasion of Sicily Armistice of Cassibile June 6, 1944, order of the day People of Western Europe speech Normandy landings Operation Veritable Berlin Declaration Military Governor, U.S. Occupation Zone in Germany Disarmed Enemy Forces European Advisory Commission Supreme Commander of NATO, 1951-1952 Presidency (timeline) Transition 1953 inauguration 1957 inauguration State of the Union Address 1953 1954 1955 1956 1957 1958 1959 1960 1961 Cabinet Judicial appointments Supreme Court Farewell address "Military–industrial complex" Kennedy transition Executive Orders Presidential Proclamations Foreign policy Eisenhower Doctrine Korean War 1953; Korean Armistice Agreement 1953 Iranian coup d'état "Chance for Peace" speech (1953) Cold War Domino theory Khrushchev, Eisenhower and De-Stalinization New Look policy Massive retaliation 1955 Geneva Summit 1960 U-2 incident Atomic Energy Act of 1954 Atoms for Peace Restricted Data Agricultural Trade Development and Assistance Act of 1954 Food for Peace Suez Crisis (1956) DARPA (1958) EURATOM Cooperation Act of 1958 National Aeronautics and Space Act 1958; NASA Operation 40 (1960) Domestic policy Executive Order 10479 (1953) Outer Continental Shelf Act (1953) Refugee Relief Act (1953) Submerged Lands Act (1953) U.S. Department of Health, Education, and Welfare (1953) Agricultural Act of 1954 National Wool Act of 1954 Special Milk Program Excise Tax Reduction Act of 1954 Internal Revenue Code of 1954 Watershed Protection and Flood Prevention Act of 1954 Small Watershed Program Air Pollution Control Act of 1955 Agricultural Act of 1956 Soil Bank Act Soil Bank Program Federal Voting Assistance Program (1955) Bank Holding Company Act (1956) Federal-Aid Highway Act of 1956 Interstate Highway System Highway Trust Fund Fish and Wildlife Act (1956) People to People Student Ambassador Program (1956) President's Council on Physical Fitness and Sports (1956) Civil Rights Act of 1957 U.S. Commission on Civil Rights U.S. Department of Justice Civil Rights Division Federal Plant Pest Act of 1957 Little Rock Nine intervention (1957) Price–Anderson Nuclear Industries Indemnity Act (1957) Alaska Statehood Act (1958) Humane Slaughter Act (1958) National Defense Education Act 1958; Federal Perkins Loan Student loans in the United States Hawaii Admission Act (1959) Multiple-Use Sustained-Yield Act of 1960 Civil Rights Act of 1960 Sikes Act (1960) Books Crusade in Europe (1948) Elections Primaries Draft Eisenhower movement 1948 1952 1956 Republican National Conventions 1952 Vice presidential candidate selection Logistics Television broadcasts 1956 General elections 1952 1956 Legacy Bibliography Birthplace Eisenhower Presidential Library, Museum, gravesite Boyhood home Eisenhower National Historic Site, home and farm Eisenhower House Dwight D. Eisenhower Memorial Eisenhower Executive Office Building Wichita Dwight D. Eisenhower National Airport Eisenhower Fellowships Eisenhower Institute Eisenhower Monument Eisenhower dollar Eisenhower Centennial silver dollar U.S. Postage stamps Dwight D. Eisenhower Army Medical Center Eisenhower Medical Center Eisenhower Trophy Eisenhower Tunnel Eisenhower Golf Club Eisenhower Theater Statue of Dwight D. Eisenhower (U.S. Capitol) Fort Eisenhower Mount Eisenhower White House putting green Eisenhower College Places named for Eisenhower Other tributes and memorials Popular culture Eisenhower jacket Eisenhower Tree Crusade in Europe (1949 television series) Backstairs at the White House (1979 miniseries) Ike (1979 miniseries) Ike: Countdown to D-Day (2004 film) Pressure (2014 play) Family Mary "Mamie" Geneva Doud Eisenhower (wife) John Eisenhower (son) David Eisenhower (grandson) Anne Eisenhower (granddaughter) Susan Eisenhower (granddaughter) Mary Jean Eisenhower (granddaughter) Jennie Eisenhower (great-granddaughter) Ida Stover Eisenhower (mother) Arthur Eisenhower (brother) Edgar N. Eisenhower (brother) Roy Eisenhower (brother) Earl D. Eisenhower (brother) Milton S. Eisenhower (brother) Related Eisenhower baseball controversy Camp David "And I don't care what it is" Atoms for Peace Award Introduction to Outer Space Eddie Slovik Kay Summersby ← Harry S. Truman John F. Kennedy → Category

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Adapted from the Wikipedia article [Restricted Data](https://en.wikipedia.org/wiki/Restricted_Data) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Restricted_Data?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.