Keeping Track of the Bomb

The U.S. Nuclear Weapons Cost Study Project was completed in August 1998 and resulted in the book Atomic Audit: The Costs and Consequences of U.S. Nuclear Weapons Since 1940 edited by Stephen I. Schwartz. These project pages should be considered historical.

Once built, every nuclear weapon was assigned a unique serial number.


This number is permanently emplaced by engraving or etching it onto the weapon. These numbers are used by the DOE and the DSWA (formerly the Defense Nuclear Agency) to track changes in custody, current weapon configurations, and changes in location. Since 1952, the DSWA and its predecessors have been charged by the Secretary of Defense and the Chairman of the Joint Chiefs of Staff with inspecting and certifying all nuclear-capable units through a process known as a defense nuclear surety inspection (for the Air Force) or a Navy technical proficiency inspection.


According to the DSWA, the inspection team currently consists of eleven personnel. No unit is permitted to exceed sixty months between inspections. Only a portion of the stockpile is examined each year (in the mid-1970s the sample size was 20-25 percent; today it is about 25 percent). In the 1970s the military units themselves were responsible for selecting the weapons to be inspected (DOD told GAO in 1977 that operational missions, training, and routine maintenance all took priority over inspections and that giving DNA the authority to select weapons to be inventoried was undesirable from the standpoint of military readiness). Today, DSWA inspection teams are responsible for selecting weapons for physical inspection. The military services also conduct their own inspections of certified nuclear units at least every eighteen months, with inspection teams ranging in size from 6 to 150 personnel, depending on the characteristics of the unit involved.

In addition to the weapons inventory, DSWA officials review management records, technical operations, security, and safety. In the mid-1970s (and presumably before), each nuclear-capable unit performed semi-annual inspects to reconcile its lists with those maintained by DSWA and reported its findings to DSWA. However, many weapons on alert or emplaced in inaccessible containers were not physically inspected in this manner. Both the DOE and DSWA maintain secure computerized databases for this tracking information. A 1977 investigation by the General Accounting Office found the system immune to tampering and an accurate record of the current stockpile.



Drawn from U.S. General Accounting Office,

Accountability and Control of Warheads in the Custody of the Department of Defense and the Energy Research and Development Administration,

PSAD-77-115 (June 2, 1977); information provided via facsimile by Cheri E. Abdelnour, Public Affairs Office, Defense Special Weapons Agency, to Stephen I. Schwartz, February 1, 1998; and William M. Arkin, Robert S. Norris, and Joshua Handler,

Taking Stock: Worldwide Nuclear Deployments, 1998

(Washington, D.C.: Natural Resources Defense Council, March 1998), pp. 21-22.



A nuclear capable unit is defined as one certified by one of the three services, or, in the case of European units, the European command, as having the capability for assembly, maintenance, or storage of nuclear weapons, associated components, and ancillary equipment. There currently are about sixty-one nuclear-capable units in the U.S. military (thirty-four Navy, twenty-six Air Force, and one Army).


Copyright © 1998 The Brookings Institution