added to acamedia cache on Feb. 3, 2006



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

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.


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.

[ Plutonium Sub-Directory ] [ COMPLETE DIRECTORY ]

Since March 27th 1996, there have been over
100,000 outside visits to the CCNR web site, plus

(counter reset June 3rd 1998 at midnight)