Nuclear Bomb Dropped in Georgia
No Nuclear Capsule Inserted, Documents Show

Several news papers have carried stories about a nuclear weapon that was dropped by a U.S. Air Force B-47 strategic bomber near Savanna River in Georgia on February 5, 1958. The weapon has never been recovered and some papers have stated that the weapon could explode with a nuclear yield or that radioactive materials may have leaked from the weapon.

Documents released by the Air Force and obtained under FOIA help alleviate some of the rumors about the accident.

For years the Air Force has been less than forthcoming with information about the accident, but in April 2001 the Air Force released a Search and Recover Assessment of the accident the gave new information about the weapon. This report disclosed that the weapon was a Mk-15 Mod 0 and that the nuclear capsule was not inserted at the time of the accident (download Air Force document in the right-hand bar).

In addition, the Temporary Custodian Receipt used to transfer the weapon from the Atomic Energy Commission (AEC) to the Air Force in 1958 has been released under FOIA. It confirms that the weapon was the Mk-15 Mod 0, and that AEC did not "allow any active capsule to be inserted into it at any time." (download Air Force document in the right-hand bar).

Mk-15 thermonuclear bomb similar to the one dropped
near Savannah River in 1958. Source: U.S. Air Force.

Another FOIA document, the History of Strategic Air Command (SAC) for January-June 1958, provides important background information to understand the management of nuclear weapons custody at the time. The document also provides information about weapons design and the risk of accidental nuclear explosion in accidents like that at Savanna River (download Air Force document in the right-hand bar).

Shortly after the Savannah River accident, the design of the Mk-15 was changed from insertable component to sealed-pit (designated Mk-15 Mod 2).  This was completed in May 1958.  But the first sealed-pit weapons were not delivered to the Air Force until June 1958, four months after the Savanna River accident.

Had the capsule been inserted in the weapon jettisoned at Savannah River, the SAC history shows, the probability of a nuclear explosion would have been significant: a 15 percent probability of up to 40.000 pounds of nuclear yield in the event of one point detonation. The design of pit weapons improved safety considerably, but a significant risk of accidental nuclear explosion remained:

"...there was no significant degradation of safety when flying [a sealed-pit weapon] with safety pins installed and the U-2 rack locked. There was, however, a significant degradation of safety if the weapon was involved in an aircraft crash or was jettisoned with the safety pins removed. The estimated probability of a nuclear detonation of the weapon in a crash with pins removed was one in ten thousand. The estimated probability of a nuclear detonation if the weapon was jettisoned or an inadvertent release occurred with pins removed was one in five hundred."
Source: Memo, Col Roland A. Campbell, Ch. Ops Div, D/Ops, to General Terrill, "USAF Safety Review of Sealed Pit Weapons," January 14, 1958.

The accident at Savannah River, however, is not included in the SAC history. The document includes descriptions of three B-47 crashes during the first half of 1958, but does not mention the mid-air collision between the B-47 and a F-86 near Savannah, Georgia.