NNSA Completes First Production Unit of W76/Mk4B Reentry Body

WASHINGTON - The Department of Energy's National Nuclear Security Administration (DOE/NNSA) completed the first unit of the Mark (Mk) 4B reentry body for the W76 nuclear warhead supporting sea-based strategic deterrence. The Mk4B protects the submarine-launched ballistic missile warhead when reentering Earth's atmosphere. NNSA worked alongside U.S. Navy counterparts to enhance the reliability of the previous Mk4As. The first W76/Mk4B unit was manufactured nearly three months ahead of schedule.

"NNSA is making good on our commitment to accelerate production for the nation's nuclear deterrent and delivering the first W76/Mk4B to the Navy ahead of schedule" said NNSA Administrator Brandon Williams. "As a former nuclear submarine officer, I have a special appreciation for the sea leg of our triad, which is essential to our assured second-strike capability. Enhancing the reliability of the W76's reentry body will help ensure the reliability of the deterrent and strengthen America's national security more broadly."

To accelerate production of the first W76/Mk4B unit, NNSA was enabled by major contributions from across the Nuclear Security Enterprise. The Pantex Plant capitalized on a previous readiness determination conducted for the W76-1 a year prior in collaboration with the Nuclear Explosive Safety Study team. At the same time, Kansas City National Security Campus completed critical non-nuclear components ahead of deadline, and Sandia National Laboratories and Los Alamos National Laboratory issued Qualification Evaluation Releases to meet the three-month acceleration. Enterprise elements collaborated closely on the design, development, qualification and component production for the W76/Mk4B. This collective milestone supports U.S. Department of War requirements by ensuring the sea-based leg of the nuclear deterrent continues to meet U.S. national security objectives

"The Mk4B modernization is a demonstration of NNSA's methodical approach to ensuring the reliability of U.S. strategic weapons systems and meeting deterrence requirements," said David Beck, NNSA's Deputy Administrator for Defense Programs. "This milestone underscores NNSA's ability to meet and often accelerate production schedules in response to critical national security needs."

The next major contributions to the sea-leg of the nuclear deterrent will include the W88 Alteration 376 Program, the W93 warhead, and the W80-5/nuclear-armed, sea-launched cruise missile (SLCM-N). The first production units of these warheads are expected through the early to mid-2030s