Office of Declassification
Table of Contents
This booklet is intended to assist the many Government and industry personnel who generate or review classified documents. Its purpose is to help you detect the possible presence of classified nuclear information in documents. Classified nuclear information follows different rules than other, more familiar kinds of classified information. Classified nuclear information should be marked as "Restricted Data" (RD) or "Formerly Restricted Data" (FRD). However, the Department of Energy (DOE) has found that many documents with classified nuclear information (particularly historical documents) are not marked to indicate that they contain RD or FRD. Consequently, DOE is concerned that these documents may not receive proper safeguarding and might be improperly declassified and released.
The principal goal of this booklet is to increase awareness concerning this issue during a heightened time of declassification activity and to provide initial assistance in handling collections that contain or may contain RD or FRD information. If your organization is involved in declassification activity, the DOE encourages you to request additional training and assistance. DOE provides a one and a half hour briefing for the recognition of RD and FRD and can provide other assistance as needed. Note that this booklet is unclassified and is necessarily limited in its effort to identify classified nuclear information.
This booklet is not a classification guide and does not provide the authority to declassify RD or FRD, but is intended only as an awareness tool to assist in identifying unmarked RD or FRD.
Since their introduction at the end of World War II, nuclear weapons have been seen as so radically different from other weaponry, so uniquely destructive, that extraordinary measures are needed to slow their spread. To this end, the Congress enacted the Atomic Energy Act to assure firm government control over all aspects of nuclear technology relating to the creation, design, production, or use of nuclear weapons.
The Atomic Energy Act protects nuclear weapons-related information by providing it with a unique system of classification. This statute-based system operates outside of the system established by Executive Order (EO) 12958 for all other government classified information. RD is specifically exempted from all provisions of EO 12958. In particular, RD is never subject to automatic declassification but can only be declassified by the Secretary of Energy or delegated DOE authority. RD is generally technical. Some of it has enduring value so long as it is not compromised. In the hands of an adversary a nuclear weapon based on a 40-year old design would be as great a threat as a modern weapon.
Historical Documents. Documents which are marked as RD or FRD which are 25 years old or older and determined to be permanently valuable records shall not be automatically declassified. If you have RD or FRD historical documents, you should separate and remove them from other classified documents to ensure that they are not inadvertently declassified and released under EO 12958.
Current Documents. If you are generating documents which may contain RD or FRD, you should have current classification guides to assist you. We recommend that you contact your local classification or security officer to obtain these guides. If you need further assistance, please contact the DOE Office of Declassification.
Mismarked Documents. If you come across classified documents which are not marked as RD or FRD but contain nuclear-related information described in this booklet, you should advise your local classification or security officer or seek assistance from the DOE Office of Declassification.
The Office of Declassification is undertaking a focused effort to reach Government and industry personnel with access to DOE classified information. If you have questions, need assistance, or would like more information on RD or FRD, please contact the Office of Declassification Outreach Hotline at (301) 903-7567.
This section describes the subject areas that are most likely to contain classified nuclear information, but keep in mind that these subject areas and the key word list that follows are not all inclusive.
Nuclear weapons apply the physical phenomenon of nuclear fission葉he splitting of a heavy atomic nucleus by absorption of a neutron葉o cause the explosion of kilogram quantities of uranium or plutonium and the release of explosive energy ("yield") many orders of magnitude greater than would be possible from a similar amount of ordinary high explosives. The two basic designs of these fission type weapons are the gun-assembled weapon like the Little Boy which was dropped on Hiroshima during World War II, and the implosion-assembled weapon like the Fat Man which was dropped on Nagasaki.
Some nuclear weapons also use the process of thermonuclear fusion葉he joining together of light nuclei at very high temperatures. In a boosted implosion weapon, the fusion reaction is used to produce additional neutrons and enhance (boost) the fission yield. In a thermonuclear (staged) weapon, the energy released by the fusion reaction is a significant part of the yield.
Information revealing weapon configurations, design principles and details, mode of operation, tests, yields, methods for command/control (use control), targeting information, disablement, stockpile information (storage locations, theater allocations, and maintenance information), and vulnerabilities to sabotage or countermeasures usually is classified as RD or FRD. RD or FRD (but not bearing RD or FRD markings) is perhaps most likely to be found in documents dealing with weapon delivery systems such as missiles or aircraft, or with defense against such systems.
This laboratory-scale research attempts to use certain directed power sources葉ypically very large lasers but also accelerator-produced particle beams葉o compress and heat a tiny target containing small quantities of fusion fuel (deuterium and tritium) to thermonuclear ignition conditions. The resulting "microexplosion" resembles a miniaturized thermonuclear weapon. Therefore, target design and operation information judged to be particularly revealing of related nuclear weapons technology is classified as RD.
Nuclear reactors use the fission reaction to generate energy for conversion to electric power or other application, but in a much slower, controlled manner than occurs in a nuclear explosion. Information in this area that is still classified as RD includes design, development, testing, and operation of reactor power systems for military purposes, especially for naval nuclear propulsion, and information concerning capabilities and vulnerabilities. The emphasis here is on "military" or "naval" since all aspects of civilian nuclear power (e.g., commercial electric power generation) are unclassified.
The most certain way to discourage the proliferation of nuclear weapons is to deny access to critical materials needed for nuclear weapon production. Numerous materials are needed; however, the most costly and technically difficult materials to produce are the most important. These include fissile materials such as plutonium-239 (Pu-239) and uranium-235 (U-235) as well as tritium, an isotope of hydrogen. The costly and elaborate methods developed to produce these materials are still classified as RD. Generally, there are two main methods used to produce these materials: production reactors and isotopic enrichment.
Plutonium does not occur naturally but must be produced in specially designed nuclear reactors (production reactors). The hydrogen isotope tritium required for boosting fission weapons is also made in such reactors. Information describing the nuclear fuel and "target" elements used in the reactors and other detailed features of the production process may be classified as RD. Vacuum furnace operations, chemical separation, and isotope enrichment are all used in producing the final products from these reactors and details about these operations may be classified as RD.
Unlike plutonium, uranium occurs naturally and is relatively plentiful. However, only the lighter isotope U-235, which makes up only 0.7% of the natural element, is useful for a fission explosion. Extracting this isotope from natural uranium requires a process that can separate the U-235 from the slightly heavier but much more common isotope U-238. This has been done by diffusion techniques (gaseous diffusion), which exploit slight thermal speed differences between gas molecules containing the different isotopes; by centrifuge, which exploits the difference in inertial mass; and by laser separation techniques, which exploit isotopic differences in atomic spectra. Information potentially classified as RD includes process and design details of these different isotope separation methods, and the amounts and specifications of material prepared for the weapons program. Of particular concern for the gaseous diffusion method of separation is the protection of barrier technology which refers to specialized "barriers" through which the gas diffuses.
Key sites and organizations that may be found in conjunction with nuclear information and potential RD:
The markings listed below indicate that the document may contain RD or FRD, even if not otherwise marked: