The National Nuclear Security Administration (NNSA) announced that it had completed on Jan. 9 its eight-year effort to refurbish the B61-7 and B61-11 strategic nuclear bombs.
The B61-7 and B61-11 are gravity bombs, deliverable by B-52H or B-2A strategic bombers, with varying explosive yields up to 360 kilotons. The steel-encased B61-11 was designed to have earth-penetrating, or bunker busting, capabilities of up to six meters. According to a report published in 2007 by the Natural Resources Defense Council, the U.S. stockpile contains an estimated 215 operational B61-7 bombs and 20 operational B61-11 bombs. The number of actively deployed B61-7s is expected to be reduced to 120 by 2012.
Since 1992, when the United States began observing a moratorium on nuclear testing, policymakers have debated how best to ensure the safety and reliability of the nuclear arsenal. In 1993 Congress introduced the Stockpile Stewardship Program in order to evaluate and address age-related effects on nuclear weapons. In response to this congressional mandate, the NNSA created the Life Extension Program (LEP). Under this program, the NNSA is able to extend the life of its existing nuclear weapons an additional 20 or 30 years without designing new weapons systems.
In contrast, the Reliable Replacement Warhead (RRW) program would permit the design of new warheads and weapon systems. The Bush administration supported the RRW initiative, but Congress has not funded the controversial program for the past two years, preventing the NNSA from proceeding with its new WR1 warhead design. (See ACT, December 2008.)
Work on B61 refurbishment began in 2000 as part of the NNSA's LEP. The B61 presents unique challenges not only because of its complex engineering but also because it is among the oldest designs in the U.S. nuclear arsenal. (See ACT, December 2008.) The original B61-1was introduced in 1969, and most of the B61s in the arsenal were produced during the 1960s and 1970s.
In February, the NNSA announced that the first refurbished W76 warhead had entered the nuclear stockpile after a 10-year effort to extend its life. The W76 was added to the U.S. arsenal in 1978.
Refurbishments often involve repairing or replacing parts that have deteriorated over time. The renovation of the B61 has involved overhauling the canned subassembly, which is the steel housing for the warhead secondary, as well as replacing various supports and cables. The first refurbished B61s were delivered in 2006 despite some early problems in the program. In a Department of Energy audit report released in August 2005, investigators reported several issues, including technical problems, testing delays, and unsatisfactory program management. According to the report, the NNSA was receptive to the Energy Department's recommendations and sought to complete the refurbishment on time.
The January announcement reported that final refurbishments were completed one year early. In the NNSA press release, Deputy Administrator for Defense Robert Smolen boasted that "[t]his is the culmination of an ambitious continuing effort which helped to ensure that the nation's aging nuclear weapons stockpile continues to be reliable."