Advanced Simulation and Computing and Institutional R&D Programs


The Advanced Simulation and Computing (ASC) Program supports the Department of Energy’s National Nuclear Security Administration (DOE/NNSA) Defense Programs’ use of simulation-based evaluation of the nation’s nuclear weapons stockpile. The ASC Program is responsible for providing the simulation tools and computing environments required to qualify and certify the nation’s nuclear deterrent in the absence of underground, full-system nuclear weapons tests. At its core, the ASC Program is a science-based endeavor that integrates a deep understanding of the details of nuclear weapons safety, science and performance with surrogate numerical experiments enabled by a powerful computing infrastructure.



DOE/NNSA is charged with supporting the nation’s nuclear deterrent by maintaining a safe, secure, and effective nuclear weapons stockpile for as long as nuclear weapons exist, that will deter adversaries and assure allies. To maintain a credible nuclear weapons program in the absence of full-scale underground nuclear testing, the NNSA’s Office of Defense Programs needs to ensure that the capabilities, tools, and expert staff are in place and are able to deliver validated assessments.  Without nuclear testing as the final arbiter of scientific judgment, weapons scientists and engineers must rely much more heavily on sophisticated computational models run on incredibly powerful computers that simulate the complexities of nuclear physics, weapons components, the weapons systems as a whole, and determine the impact of design changes and aging on the nuclear weapons stockpile. This requires a robust simulation environment in combination with a strong experimental program.

The ASC Program continually works to meet national needs—economically, efficiently, and within the scope set by Congress—to assure those who provide the resources that their funds are well invested. To this end, the ASC Program invests in the following goals:

  • Improving the confidence in prediction through simulations;
  • Developing the ability to quantify confidence bounds on the uncertainty in computational results;
  • Increasing predictive capability through tighter integration of simulation and experimental activities;
  • Providing the necessary computing capability to code users, in collaboration with industrial partners, academia, and government agencies.

ASC Program Background

For nearly a half century, confidence in the U.S. nuclear deterrent was a product of computation, experimental science, and weapons physics. The final judgments about the safety, performance, and reliability of the country’s nuclear stockpile were confirmed by nuclear test.  However, the US conducted its last nuclear test in 1992, and, in 1996, signed the Comprehensive Test Ban Treaty, thereby choosing to end reliance on full-scale nuclear testing as the final confirmation.  In addition, the current stockpile is comprised of weapons systems that have been required to remain in the stockpile for decades longer than originally planned. 

The NNSA’s Science-Based Stockpile Stewardship Program (SSP) was established to develop new tools for assessing the performance of nuclear weapon systems, predict their safety and reliability, and certify their functionality. The program must fulfill its responsibilities without nuclear testing, and must also redress constraints on non-nuclear testing, the downsizing of production capabilities, and the cessation of the development of new weapon systems to replace existing weapons. Further complicating matters, weapon components are exceeding their design lifetimes, and manufacturing issues and environmental concerns force changes in fabrication processes and materials of weapon components.

The predecessor to ASC, the Accelerated Strategic Computing Initiative (ASCI), was established in 1995 as an element of the SSP to provide nuclear weapons simulation and modeling capabilities. Due to its successful outcome as an initiative, ASCI was formalized in 2004 as the Advanced Simulation and Computing (ASC) Program. Continuing the trailblazing path of ASCI, ASC integrates the work of three Defense programs laboratories (Lawrence Livermore National Laboratory, Los Alamos National Laboratory, and Sandia National Laboratories) and university researchers nation-wide into a coordinated program administered by NNSA. Under continuous development due to evolving SSP requirements, the laboratory-developed codes embody the best understanding of the physics and engineering of the nuclear stockpile and are a central contributor to achieving SSP missions.

Related Links:

Lawrence Livermore National Laboratory's ASC Program off site link
Los Alamos National Laboratory's ASC Program off site link
Sandia National Laboratories' ASC Program off site link