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The W76/Mk4 reentry body assembly (RBA) on Trident I (C4) and Trident II (D5) strategic weapon systems are a key component of the Nation's strategic deterrent force designed and produced between 1972 and 1987. Meeting this mission will require that the W76/Mk4 RBA be deployed well beyond its original service life of 20 years.

Aging concerns, the non-availability of replacement components used in original designs, and a desire to modernize nuclear safety features requires a refurbishment of the W76/Mk4 RBA for it to meet the extended service life. This should be accomplished in a planned, methodological manner to prevent possible weapon downtime and the total consumption of the National Nuclear Security Agency (NNSA) nuclear weapons complex capacity that could occur if a critical problem were identified. The US Navy Strategic Systems Programs (SSP) requested and the Nuclear Weapons Council Standing and Safety Committee (NWCSSC) approved a joint Department of Defense (DOD)/DOE Phase 6.2/6.2A Study, which was initiated on 19 October 1998. The study was conducted under the W76/Mk4 Project Officers Group (POG). The results of the study were briefed by the W76/Mk4 POG to the NWCSSC on 8 December 1999 and to the Nuclear Weapons Council (NWC) on 13 March 2000.

Study ground rules included the following:

  • Modernize nuclear detonation safety features (to Mk5-like interface)
  • Consider W76/Mk4 on Trident II (D5) only
  • Current W76/Mk4 Military Characteristics (MCs) and Stockpile-To-Sequence (STS) were baseline
  • Plan for a one-time refurbishment process (DOD and NNSA)
  • Plan for total stockpile quantities reflected in the current Long Range Planning Assessment (LRPA)
  • Production duration goal of 10 years or less
  • Goal for a post-refurbishment life extension of 30 years

Emphasis was placed on meeting performance requirements over the extended life and minimizing the cost of necessary refurbishment.

The drivers for refurbishment are fourfold:

  1. The W76/Mk4 is the most critical element of our nation's strategic deterrent and cannot be allowed to be degraded by a serious aging problem;
  2. The W76/Mk4 Dual Revalidation Program has shown that even though components are aging gracefully, there are some negative changes;
  3. The Stockpile Surveillance Program cannot predict failures; rather, it only detects them when they appear and when it may be too late to prevent degradation; and
  4. The Navy has expressed the desire to retain an average system age of no more than 30 years, compatible with life extension of the Trident Weapon system.

The POG-recommended refurbishment option meets the life extension requirements for the W76/Mk4, while enhancing surety and providing increased targeting flexibility and effectiveness. Careful examination of technical, certification, and compatibility issues have identified no unacceptable program risks. DOD and NNSA costs have been identified to the degree appropriate for this phase of the program. Based on these factors, the POG recommended refurbishment of the W76/Mk4 beginning on 1 April 2000.

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