Additional Information Concerning Underground Nuclear Weapon Test of
Reactor-Grade Plutonium
U.S. Department of Energy, Office of the Press Secretary, Washington, DC
20585
Additional Information Concerning Underground Nuclear Weapon Test of
Reactor-Grade
Plutonium
Specifically
Background
Benefits
Who Are the Key Stakeholders?
Contact
Questions and Answers
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.
- 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.
- 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.
- 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.
- 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.
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
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.
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