U.S. Department of Energy, Office of the Press Secretary, Washington, DC 20585

Additional Information Concerning Underground Nuclear Weapon Test of Reactor-Grade Plutonium

Table of Contents

The Department of Energy is providing additional information related to a 1962 underground nuclear test at the Nevada Test Site that used reactor-grade plutonium in the nuclear explosive.

Specifically

• A successful test was conducted in 1962, which used reactor-grade plutonium in the nuclear explosive in place of weapon-grade plutonium.
• The yield was less than 20 kilotons.

Background

• This test was conducted to obtain nuclear design information concerning the feasibility of using reactor-grade plutonium as the nuclear explosive material.
• The test confirmed that reactor-grade plutonium could be used to make a nuclear explosive. This fact was declassified in July 1977.
• The release of additional information was deemed important to enhance public awareness of nuclear proliferation issues associated with reactor-grade plutonium that can be separated during reprocessing of spent commercial reactor fuel.
• The United States maintains an extensive nuclear test data base and predictive capabilities. This information, combined with the results of this low yield test, reveals that weapons can be constructed with reactor-grade plutonium.
• Prior to the 1970's, there were only two terms in use to define plutonium grades: weapon-grade (no more than 7 percent Pu-240) and reactor-grade (greater than 7 percent Pu-240). In the early 1970's, the term fuel-grade (approximately 7 percent to 19 percent Pu-240) came into use, which shifted the reactor-grade definition 19 percent or greater Pu-240.

Benefits

• As part of the Secretary of Energy's Openness Initiative, the Department of Energy is providing additional information regarding a 1962 underground nuclear test that used reactor-grade plutonium. As a result, the American public will have information that is important to the current debate over nonproliferation issues associated with reactor-grade plutonium that can be separated during spent fuel reprocessing and the importance of international safeguards. The release of this information should encourage other nations to declassify similar test information.
• This information will be useful in the international arena in defining the nonproliferation regime for separated reactor-grade plutonium. It will be useful in confirming and underpinning the requirements for international safeguards.
• This information will correct erroneous statements made elsewhere about the potential use of reactor-grade fuel for nuclear weapons.

Who Are the Key Stakeholders?

• The Public. This information will be useful to nonproliferation public interest groups who are debating nuclear proliferation issues.
• Public Interest Organizations. Stakeholders include environmental, safety and health groups, historians, archivists, researchers, scientists, and industrial workers, as well as State and Federal personnel. Those interested in oversight of nuclear weapons testing related activities will have additional information regarding the nuclear test of reactor-grade plutonium. Public interest organizations which have expressed such an interest include (but are not limited to): Energy Research Foundation, Environmental Information Network, Friends of the Earth, Greenpeace, Institute for Science and International Security, League of Women Voters, Military Production Network, National Association of Atomic Veterans, National Security Archive, Natural Resources Defense Council, Nevada Desert Experience, Nuclear Control Institute, Physicians for Social Responsibility, Plutonium Challenge, Sierra Club, University of Sussex/England, and the Western States Legal Foundation.
• Environmentalists. With this declassification, those interested in environmental oversight of plutonium related activities will have additional information regarding the utility of reactor-grade plutonium. Those interested include Greenpeace, Institute for Science and International Security, Nuclear Control Institute and the University of Sussex, England.

Contact

U.S. Department of Energy
Office of Public Affairs
Contact: Sam Grizzle
(202) 586-5806

U.S. Department of Energy, Office of the Press Secretary, Washington, DC 20585

QUESTIONS AND ANSWERS

Q. Why wasn't the exact yield of the event released?

A. Revelation of the yield was determined to be of value to certain proliferants.

Q. What was the quantity of reactor-grade plutonium used in the test?

A. In this circumstance, specific information would be of benefit to certain proliferants and is not releasable.

Q. What is the grade of plutonium used in U.S. nuclear weapons?

A. The United States uses weapon-grade plutonium. Weapon-grade plutonium is defined as plutonium containing no more than 7 percent plutonium-240.

Q. Why is weapon-grade plutonium better than reactor-grade plutonium in weapons?

A. Reactor-grade plutonium is significantly more radioactive which complicates its use in nuclear weapons.

Q. If this was a successful test as you indicate, why didn't the United States use reactor- grade plutonium in nuclear weapons?

A. Reactor-grade plutonium is significantly more radioactive which complicates the design, manufacture and stockpiling of weapons. Use of reactor-grade plutonium would require large expenditures for remote manufacturing facilities to minimize radiation exposure to workers. Reactor-grade plutonium use in weapons would cause concern over radiation exposure to military service personnel. In any event, Public Law 97-415 prohibits United States defense use of plutonium produced in licensed facilities, i.e., commercial reactors.

Q. What was the source of the reactor-grade plutonium?

A. The plutonium was provided by the United Kingdom under the 1958 United States/United Kingdom Mutual Defense Agreement.

Q. What was the actual plutonium isotopic composition used in this test?

A. It is the policy not to reveal the actual isotopic composition of plutonium used in specific weapons or tests to prevent releasing information which may be of assistance to proliferants.