Stockpile Stewardship Program

A flight test of an unarmed Minuteman III missile carrying an instrumented mock W87 warhead was successfully launched. Flight tests such as this provide data on the performance of key warhead components in real environments, making this a valuable element in our annual assessment process.

Since the Cold War, United States policy has pivoted from production to maintenance of the nation’s nuclear stockpile. In 1992, nuclear weapon development ceased with a national moratorium on nuclear testing. The end of the nuclear arms race dramatically affected the nation’s three weapon laboratories—Livermore, Los Alamos, and Sandia—but their central missions remain focused on national security science and technology. Although the U.S. stockpile of weapons is smaller than it used to be, nuclear deterrence remains an integral part of national security policy. In 1995, the Stockpile Stewardship Program (SSP) was born.

The Stockpile Stewardship Program is an ambitious effort to improve the science and technology for assessing an aging nuclear weapons stockpile without relying on nuclear testing. For this program to succeed, all aspects of weapons must be understood in sufficient detail so experts can evaluate weapon performance with confidence and make informed decisions about refurbishing, remanufacturing, or replacing weapons as needs arise.

LLNL’s responsibilities include developing, validating, and deploying high-fidelity, physics-based capabilities to predict, assess, and certify nuclear weapons performance.

Each year, together with Los Alamos and Sandia national laboratories, we are required to provide an assessment of the stockpile’s safety, security, and reliability to the National Nuclear Security Administration (NNSA) and the President. (Read more in Science and Technology Review: Taking the Pulse of the Stockpile.)

Today, stewardship requires constant innovation and diligence from LLNL scientists. (Read more in Science and Technology Review: Stockpile Stewardship at 20 Years.)



Life-extension programs necessitate the adoption of new manufacturing processes such as additive manufacturing. LLNL researchers produced a silicone cushion with programmable mechanical energy absorption properties through a three-dimensional printing process using a silicone-based ink.

  • Weapon Life extension. Our stewardship efforts face challenges with aging materials, older designs, and obsolescent parts for weapons with a 20-year service life. Routine surveillance, diagnostic tools, and new techniques such as additive manufacturing help our team forecast and detect material-related problems earlier.
  • Predictive modeling. In the absence of experimental testing, we develop three-dimensional simulations and other computational tools. This advanced computational power enables scientists to integrate disparate information into an assessment of weapon system performance, margins, and uncertainties.
  • Plutonium science. Over time, changes in plutonium’s chemical structure (or phase) could compromise weapons performance. Our team performs ongoing experiments to understand the element’s aging process and dynamic behavior.
  • High-explosive science. A nuclear weapon’s detonation process cannot occur without a precision-designed high explosive creating the main charge. Working at LLNL’s High Explosives Applications Facility (HEAF), our chemists have developed “insensitive” high explosives that are much less likely to accidentally detonate than conventional explosives used in most weapons.
  • High-energy-density science. Measuring strength and other dynamic properties of weapons materials requires experimentation with thermonuclear processes to validate theoretical models. We accomplish this in the post-nuclear-test era with the 192-beam laser system at the National Ignition Facility (NIF), producing extreme environments to improve understanding of weapon physics.
  • Infrastructure investments. In managing the stockpile long term, we recognize the need to create modern, state-of-the-art facilities to sustain laboratory capabilities. Retaining the skills, knowledge, and abilities of stockpile stewards is paramount, so another priority is hiring and developing the next-generation workforce.



A view inside NIF’s target chamber, which allows scientists to replicate various physical processes at energy densities and temperatures approaching those in a weapon detonation.

Stockpile stewardship is a continuous process that requires the right tools for the job. Though not without risk as weapons continue to age and national security requirements change, our efforts through SSP will continue to ensure a safe, secure, and effective stockpile as long as nuclear weapons exist.

Watch our YouTube video Stockpile Stewardship: How we ensure the nuclear deterrent without testing.