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Throughout history, U.S. national defense has required that certain information be maintained in confidence to safeguard U.S. citizens, democratic institutions, homeland security, and interactions with foreign nations. Today, preserving critical U.S. national security information remains a top priority.

The U.S. government has created a classification system for safeguarding information which includes marking and granting clearances and access to obtain or view documents containing classified information. This chapter provides a classification reference for general issues related to nuclear matters. It includes a discussion of information classification, classification authorities, security clearances, access to classified information, marking classified documents, For Official Use Only (FOUO)/Official Use Only (OUO), and Unclassified Controlled Nuclear Information (UCNI).

Information Classification

The two categories of classified information are national security information (NSI) and atomic energy (nuclear) information.

National Security Information

Executive Order (EO) 13526, Classified National Security Information, prescribes the system for classifying, safeguarding, and declassifying NSI. EO 13526 states national security information may be classified at one of the following three levels:

  • Top Secret (TS) shall be applied to information, the unauthorized disclosure of which could reasonably be expected to cause exceptionally grave damage to the national security that the original classification authority is able to identify or describe.
  • Secret (S) shall be applied to information, the unauthorized disclosure of which could reasonably be expected to cause serious damage to the national security that the original classification authority is able to identify or describe.
  • Confidential (C) shall be applied to information, the unauthorized disclosure of which could reasonably be expected to cause damage to the national security that the original classification authority is able to identify or describe.

Nuclear Information

Nuclear information is protected by the Atomic Energy Act (AEA) of 1954, as amended, and is a caveat added to the classification level of specific types of information. Information can be classifed as Secret, Restricted Data (S//RD) or TS//RD. The Department of Energy (DOE) implements the AEA requirements for classification and declassification of nuclear information via 10 CFR 1045, Nuclear Classification and Declassification. The AEA classifies nuclear information as RD, which is not subject to EO 13526. DOE controls the classification and declassification of all Restricted Data.

RD comprises all data related to: the design, manufacture, or use of nuclear weapons; production of special nuclear material (SNM); or use of SNM in the production of energy. RD does not include data removed from the Restricted Data category, i.e., data that is designated Formerly Restricted Data (FRD) or Transclassified Foreign Nuclear Information (TFNI).

FRD is still a category of classified information related to nuclear weapons. It does not mean it is formerly classified and therefore is now unclassified. 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). Information characterized as FRD is not subject to EO 13526. FRD is stored, transmitted, and destroyed in the same ways as RD of the same classification level. FRD declassification requires a joint determination by DoD and DOE.

TFNI is information—from any intelligence source-that concerns the nuclear programs of foreign governments that was removed from the RD category (by transclassification) under section 142 of the Atomic Energy Act, by past joint agreements between DOE and the Director of Central Intelligence, or past and future agreements with the Director of National Intelligence. When removed from the RD category, TFNI information is stored, transmitted, and destroyed in the same ways as NSI of the same classification level.

DoD and DOE have separate systems for controlling nuclear information, as follows.

DoD System for Controlling Nuclear Information

DoD policy governing access to and dissemination of RD is provided in DoD Instruction 5210.02, Access to and Dissemination of Restricted Data and Formerly Restricted Data. DoD categorizes RD information as Confidential RD, S//RD, or TS//RD. Critical Nuclear Weapon Design Information (CNWDI) is a DoD access control caveat for a specific subset of Restricted Data. CNWDI information is S//RD or TS//RD; it reveals the theory of operation or design of components of a thermonuclear or implosion-type fission bomb, warhead, demolition munition, or test device. Finally, DoD recognizes DOE designations of Sigma 14, Sigma 15, Sigma 18, and Sigma 20 as additional subsets of Restricted Data.

DOE System for Controlling Nuclear Information

DOE policy of categorizing Restricted Data into defined subject areas is known as the Sigma system. The Secret and Top Secret Nuclear Weapon Data (NWD) subsets of RD regard nuclear weapons, components, or explosive devices or materials that have been determined to require additional protection. The current categories of NWD are Sigma 14, Sigma 15, Sigma 18, and Sigma 20; previous Sigma categories 1-13 are no longer in use. DOE controls access to all Sigma categories on a strict need-to-know basis, and DoD personnel requiring access to Sigma information must obtain DOE approval.

DOE Order 452.7, Protection of Use Control Vulnerabilities and Designs, establishes the policy, process, and procedures for control of sensitive use control information in NWD categories Sigma 14 and Sigma 15 to ensure the dissemination of the information is restricted to individuals with a valid need-to-know.

  • Sigma 14 – Category of sensitive information, including bypass scenarios, concerning the vulnerability of nuclear weapons to a deliberate, unauthorized nuclear detonation or to the denial of authorized use.
  • Sigma 15 – Category of sensitive information concerning the design and function of nuclear weapon use control systems, features, and components. This includes use control for passive and active systems and may include security verification features or weapon design features not specifically part of a use control system.

DOE Order 452.8, Control of Nuclear Weapon Data, sustains Sigma 14 and 15 and establishes Sigma 18.

  • Sigma 18 – Category of NWD including information that allows or significantly facilitates a nation or entity to fabricate a credible nuclear weapon or nuclear explosive device based on a proven, certified, or endorsed U.S. nuclear weapon or device. This information would enable the establishment or improvement of nuclear capability without nuclear testing or with minimal research and development. DOE determines the information placed in the Sigma 18 category, which includes: complete design of a gun-assembled weapon; complete design of a primary or single stage implosion-assembled weapon; complete design of a secondary stage; weapon design codes with one-dimensional hydrodynamics and radiation transport with fission and/or thermonuclear burn; and weapon design codes with two- and three-dimensional capabilities.

DOE Order 457.1A, Nuclear Counterterrorism, provides the basis for implementing procedures regulating strict control of and access to Sigma 20 information.

  • Sigma 20 – Specific category of NWD that pertains to “crude, simple, or innovative” improvised nuclear device (IND) designs, concepts, and related manufacturing or processing pathways. Not all INDs fall within the Sigma 20 category.

Foreign Nuclear Information

Foreign nuclear information is information on foreign government nuclear programs. It includes the design, manufacture, or use of nuclear weapons; the production of SNM; or the use of SNM in the production of energy. This information is treated as RD.

Considerations for the removal of foreign nuclear information from the RD category include there being no automatic declassification of the information; DOE determination that it can be removed from RD; and the use of appropriate classification markings on the remainder of the information. At a minimum, access to the information will be the same as NSI, and it will be safeguarded based upon the classification determination. Foreign nuclear information which has been removed from RD is categorized as TFNI.

Sharing Information with the United Kingdom

DoD and DOE have joint guidelines for complying with each Department’s requirements for export controls and classified information exchange for stockpile weapon activities related to the 1958 U.S.-UK Mutual Defense Agreement (MDA), under the authorities of the AEA. Using Joint Atomic Information Exchange Group (JAIEG)-approved processes, DoD and DOE management may disclose to the United Kingdom transmissible RD, FRD, and unclassified information, which includes Controlled Unclassified Information (CUI) internal to the nuclear weapon. This disclosure may be made without a license or authorization under the International Traffic in Arms Regulations (ITAR) and without prior coordination with the relevant U.S. Military Department. RD and FRD information external to the nuclear weapon may be disclosed using JAIEG-approved processes. However, the disclosure of NSI external to the nuclear weapon, which includes classified military information, shall not be made without approval of the respective Military Department.

Questions on these processes should be referred to the Assistant Secretary of Defense for Nuclear, Chemical, and Biological Defense Programs (ASD(NCB)) and the DOE National Nuclear Security Administration (NNSA) Deputy Administrator for Defense Programs. See Chapter 10: International Programs for more information.

Classifying Documents

To properly classify a document, an individual must have classification authority. DoD Manual 5200.01-V1, DoD Information Security Program, describes two types of classification authority: original and derivative. A classifier is any person who makes a classification determination and applies a classification category to information or material. The determination may be an original classification action or derivative classification action. Proper classification enables appropriate protection of information. Persons handling information must abide by the classification markings and also not assume an unmarked document or source does not contain classified or sensitive information. The Internet, in particular, can be a source of unmarked classified information or a combination of unclassified information that is classified in aggregate.

Original Classification Authority

The authority to originally classify information may only be exercised by the President and the Vice President; agency heads and officials designated by the President; and U.S. Government officials delegated the authority pursuant to EO 13526. For NSI, the original classification authority (OCA) also serves as the declassification authority and sets the date for automatic declassification. Within DoD and DOE, only appointed government officials can serve as OCAs to classify NSI. Further, only DOE officials have OCA for RD information. The Deputy Assistant Secretary of Defense for Nuclear Matters (DASD(NM)) is the OCA for FRD.

Derivative Classification Authority

According to EO 13526, those individuals who reproduce, extract, or summarize classified information, or who apply classification markings derived from source material or as directed by a classification guide, need not possess original classification authority. Individuals who apply derivative classification markings are required to observe and respect original classification decisions and carry forward the pertinent classification markings to any newly created documents. Individuals within both DoD and DOE can use derivative classification authority on NSI, RD, and FRD information.

Security Clearances

Both DoD and DOE issue personnel security clearances governing the access of their employees and contractors to classified information.

DoD Security Clearance Levels

DoD defines a security clearance as an administrative determination by a competent authority that a person is eligible under the standards of DoD 5200.2-R, Personnel Security Program, for access to classified information. DoD clearances may be issued at the Top Secret, Secret, or Confidential level. These levels allow the individual holding the clearance, and possessing the proper needto- know, to view information classified at those levels.1

DOE Security Clearance Levels

Adhering to the information restrictions and guidelines of the AEA, DOE established a security clearance system that is implemented through DOE Order 472.2, Personnel Security, and described in DOE Order 452.8:

  • L Access Authorization is given to an individual whose duties require access to Confidential RD, Confidential/Secret FRD, or Confidential/Secret NSI.
  • Q Access Authorization is given to an individual whose duties require access to Secret/Top Secret RD, Top Secret FRD, Top Secret NSI, or any category or level of classified matter designated as communications security, cryptographic, or sensitive compartmented information.

Equating the Two Classification Systems

Figure 18.1
Figure 18.1 DoD and DOE Clearance Levels and Access

While it is not possible to directly correlate the two security clearance systems used by DoD and DOE, Figure 18.1 illustrates the clearances and highest level of access for the two Departments.

Accessing Classified Information

The two basic requirements to access classified information are appropriate clearance and need-to-know, and both must be present for an individual to view classified information. Need-to-know is confirmed by the agency controlling the information and helps govern access to information. Security administrators verify an individual’s eligibility for a certain clearance level and then grant need-to-know caveats, as needed. An individual may have access authorization of C, S, TS, or TS/SCI (special compartmented information) clearance in DoD; an individual may have L or Q access authorization in DOE. Each of these clearance levels also has an interim status, which allows the cleared person to view but not create or control documents at that level. However, an interim Secret clearance does not allow access to RD, NATO, or COMSEC (communications security) information at the Secret level. An interim TS is valid for access to TS information and Secret and Confidential levels of RD, NATO, and COMSEC information. An interim TS clearance is the equivalent of a final Secret clearance. Once given a final clearance, an individual is able to access and control documents for that level of classification. Most caveats are granted after individuals review a briefing explaining the nature of the material and sign forms. After completing this process, individuals have the appropriate clearance to access the information. The process is commonly referred to as being “read-in” for a caveat.

To be given access to Top Secret, special compartmented, or Q-level information, a individual must have a favorable Tier 5 investigation (Critical-sensitive access). Access to Confidential, Secret, or L-level information requires at Tier 3 investigation (Non-critical sensitive access).2

In both instances, only DoD, DOE, the Nuclear Regulatory Commission, and the National Aeronautics and Space Administration have the authority to grant RD and FRD access. To access CNWDI information, individuals require authorization and a briefing.

Marking Classified Documents

All classified documents require classification markings, with some differences between originally classified and derivatively classified documents.

Originally Classified Documents

EO 13526 requires certain essential markings on originally classified documents. DoD Manual 5200.01-V2 stipulates the marking requirements for classified documents, which include: portion marks, banner line, “classified by” line, reason for classification, and “declassify on” line.

Portions can be paragraphs, charts, tables, pictures, illustrations, subjects, and titles. Before each portion, a marking indicating the classification of that portion is placed in parentheses: (U) for Unclassified, (C) for Confidential, (S) for Secret, and (TS) for Top Secret. Additional control markings are included, as appropriate. Each portion has its own classification marking; its classification is not affected by any of the information or markings of other portions within the same document.

The banner line must specify the highest level of classification of the document and include the most restrictive control marking applicable. The classification is centered in both the header and footer of the document. It is typed in all capital letters and in a font size large enough to be readily visible to the reader. This marking is noted on the front cover, the title page, the first page, and the outside of the back cover. Internal pages may be marked with the overall document classification or the highest classification level of the information contained on that page.

In the lower left-hand corner of the title page, the original classification authority is identified. The OCA must be identified by name, or personal identifier, and position. If the agency of the original classifier is not readily apparent, it must be placed below the “classified by” line.

The “reason for classification” designation is placed immediately below the “classified by” line. This line should contain a brief reference to the classification category or classification guidance. The number 1.4 may appear with corresponding letters, representing Section 1.4 of EO 13526 and the classification categories it defines. The information being classified must relate to one or more of the following:

  • military plans, weapons systems, or operations;
  • foreign government information;
  • intelligence activities (including covert action), intelligence sources or methods, or cryptology;
  • foreign relations or foreign activities of the United States, including confidential sources;
  • scientific, technological, or economic matters relating to national security;
  • U.S. government programs for safeguarding nuclear materials or facilities;
  • vulnerabilities or capabilities of systems, installations, infrastructures, projects, plans, or protection services relating to national security; and
  • the development, production, or use of weapons of mass destruction.

The final essential marking is the “declassify on” line. All documents must have a declassification date or event entered onto the “declassify on” line. The OCA determines the “declassify on” date using one of the three following guidelines:

  • When possible, identify the date or event for declassification that corresponds to the lapse of the information’s national security sensitivity. The date or event shall not exceed 10 years from the date of the original classification.
  • When a specific date or event cannot be determined, identify the date that is 10 years from the date of the original classification.
  • If the sensitivity of the information warrants protection beyond 10 years, then the original classification authority may assign a declassification date up to, but no more than, 25 years from the date of original classification.

For dates 25 years and beyond, refer to DoD Manual 5200.01-V2 for guidance.3

Derivatively Classified Documents

Derivative classification is the act of incorporating, paraphrasing, restating, or generating in a new form information already classified and marking the newly developed material consistent with the markings of the source information. The source information ordinarily consists of a classified document or a classification guide issued by an OCA. It is important to note that DoD can only derivatively classify documents containing RD; DOE retains original classification authority for all RD material.

Single or Multiple Source Documents

When using a classified source document as the basis for derivative classification, the markings on the source document determine the markings applied to the derivative document. As with documents created by original classifiers, each derivative document must have portion markings and overall classification markings.

Derivatively classified documents are handled in much the same manner as originally classified documents, with two differences. In a document derived from a single source, portion markings, overall markings, and, “declassify on” lines all remain the same as the original document. In a document derived from multiple sources, it is necessary to determine which source document requires the longest period of classification before marking the document with the “declassify on” line. Once that has been determined, the derivative document should reflect the longest period of classification in the source documents.

In a derivatively classified document, the “classified by” line identifies the name and position of the individual classifying the document, followed by the derivative classifier’s agency and office of origin. In addition, a derivatively classified document includes a “derived from” line. In a document derived from a single source, a brief description of the source document is used to determine the classification of the material.

Documents where classifications are derived from multiple sources are created in the same manner as documents derived from a single classified source. Enter “multiple sources” on the “derived from” line. On a separate sheet of paper, a list of all classification sources must be maintained and included as an attachment to the document. When classifying a document from a source document marked “multiple sources,” do not mark the derived document with “multiple sources.” Instead, in the “derived from” line, identify the source document. In both cases, the “reason” line, as reflected in a source document or classification guide, is not required to be transferred to a derivatively classified document.

Derivative Classification Using a Classification Guide

A classification guide is a document issued by an OCA that provides classification instructions. A classification guide describes the elements of information that must be protected and the level, reason, and duration of classification. When using a classification guide to determine classification, insert the name of the classification guide on the “derived from” line. Portion markings are determined by the level of classification of the information as listed in the classification guide and the overall marking is determined by the highest level of the portion markings contained within the document. Finally, the “declassified on” line is determined by the classification duration instruction in the guide.

Marking Restricted Data, Formerly Restricted Data, and CNWDI Documents

There is a special requirement for marking RD, FRD, and CNWDI documents. The front page of documents containing RD must include the following statement:

This document contains Restricted Data, as defined in the Atomic Energy Act of 1954. Unauthorized disclosure is subject to administrative and criminal sanctions.

This may appear on the first page of the document and on a second cover page, placed immediately after the initial classified cover sheet.

FRD material must contain the following statement on the front page of the document:

Unauthorized disclosure is subject to administrative and criminal sanctions. Handle as Restricted Data in foreign dissemination, per section 144b, Atomic Energy Act of 1954.

Additionally, documents containing RD and FRD should have abbreviated markings included with the classification portion marking (e.g., S//RD or S//FRD). Documents containing RD and CNWDI material must also contain the following statement, in addition to the RD statement on the front page of the document:

Critical Nuclear Weapon Design Information. DoD Instruction 5210.02 applies.

In addition, CNWDI is marked with an “N” in separate parentheses following the portion marking (e.g., (S//RD)(N)).

Finally, when a document contains RD, FRD, and CNWDI, only the RD and CNWDI warning notices are affixed. No declassification instructions are used.


ATOMAL is a NATO term used to identify and protect Restricted Data or Formerly Restricted Data provided to NATO by the U.S. government. Because materials marked RD or FRD are not cleared for release to NATO or NATO countries, organizations wanting to transmit RD or FRD materials to NATO must clear the materials through the JAIEG. RD or FRD materials cleared by the JAEIG for release will be assigned a JAEIG reference number (JRN). If the document is modified after a JRN has been assigned, it will require an additional JAEIG review.

The originating organization, or JAEIG in limited situations, will convert the U.S. classification markings to NATO ATOMAL as required by the Administrative Arrangements to Implement the Agreement Between the Parties to the North Atlantic Treaty for Co-operation Regarding ATOMAL Information. These materials, although marked as ATOMAL, have not been assigned a NATO registry control number and are therefore not considered NATO materials; they can still be disseminated between DoD components via secure email (SIPRNET) in the same manner as FRD materials. Once the document is formally handed over to a NATO registry and assigned a NATO control number, it becomes a controlled NATO ATOMAL document.

For Official Use Only and Unclassified Controlled Nuclear Information

FOUO and OUO are terms used by DoD and DOE, respectively, that can be applied to certain unclassified information. FOUO and OUO designations indicate information with the potential to damage governmental, commercial, or private interests if disseminated to persons who do not need to know the information to perform their jobs or other agency-authorized activities. This information may be exempt from mandatory release under one of nine applicable Freedom of Information Act (FOIA) exemptions:

  1. Records that are properly and currently classified in the interest of national defense or foreign policy.
  2. Records related solely to the internal personnel rules and practices of the DoD or any DoD Component.
  3. Information specifically exempted by a statute establishing particular criteria for withholding. The language of the statute must clearly state the information will not be disclosed.
  4. Information, such as trade secrets and commercial or financial information, obtained from a company on a privileged or confidential basis that, if released, would result in competitive harm to the company, impair the government’s ability to obtain similar information in the future, or protect the government’s interest in compliance with program effectiveness.
  5. Interagency memoranda that are deliberative in nature. This exemption is appropriate for internal documents part of the decisionmaking process and contain subjective evaluations, opinions, and recommendations.
  6. Information, the release of which could reasonably be expected to constitute a clearly unwarranted invasion of the personal privacy of individuals.
  7. Records or information compiled for law enforcement purposes that could reasonably be expected to interfere with law enforcement proceedings; would deprive an individual of a right to a fair trial or impartial adjudication; could reasonably be expected to constitute an unwarranted invasion of the personal privacy of others; disclose the identity of a confidential source; disclose investigative techniques and procedures; or could reasonably be expected to endanger the life or physical safety of any individual.
  8. Certain records of agencies responsible for supervision of financial institutions.
  9. Geological and geophysical information concerning wells.

DoD and DOE also use the term Unclassified Controlled Nuclear Information. DoD defines UCNI as unclassified information pertaining to security measures, including plans, procedures, and equipment, for the physical protection of DoD SNM, weapons, equipment, or facilities. While this information is not formally classified, it is restricted in its distribution. DoD UCNI policy is provided in DoD Instruction 5210.83, DoD Unclassified Controlled Nuclear Information. DOE uses the term UCNI in a broader manner than DoD. Designating DoD information as UCNI is governed by Title 10 USC §128, whereas designating DOE information as UCNI is governed by Title 42 USC §2168.

1 “Need-to-know” is defined in DoD 5200.2-R as a determination made by a possessor of classified information that a prospective recipient, in the interest of national security, has a requirement for access to, knowledge of, or possession of classified information in order to perform tasks or services essential to the fulfillment of an official U.S. government program. Knowledge of, possession of, or access to classified information shall not be afforded to any individual solely by virtue of the individual’s office, position, or security clearance.

2 In 2012, the Office of the Director of National Intelligence (ODNI) and the Office of Personnel Management (OPM) began collaborating on development of new standards in order to provide quality control and consistency among investigations and in October 2016, OPM established the Tier access eligibility investigation system. Tier 5 investigation replaced the single scope background investigation (SSBI) and Tier 3 replaced the national agency check with National Agency Check with Law and Credit (NACLC) investigation.

3 RD and FRD have no automatic declassification timeline. RD can only be declassified by DOE; FRD can only be declassified by a joint DoD-DOE decision.