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 results. Because of this, computer models much simpler than those needed today could be used with the best available computers to help design, modernize, and maintain the stockpile. Now, without nuclear testing as the final arbiter of scientific judgment, weapons scientists must rely much more heavily on sophisticated computers to simulate the complex aging process of the weapons components and the weapons systems as a whole, and determine the impact on the nuclear weapons stockpile.
ASC Program Background
The predecessor to ASC, the Accelerated Strategic Computing Initiative (ASCI), was established in 1995 as an essential element of the SSP to provide nuclear weapons simulation and modeling capabilities. Prior to the start of the nuclear testing moratorium in October 1992, the nuclear weapons stockpile was maintained through (1) underground nuclear testing and surveillance activities and (2) “modernization” (i.e., development of new weapons systems). A consequence of the nuclear test ban is that the safety, performance, and reliability of U.S. nuclear weapons must be ensured by other means for systems far beyond the lifetimes originally envisioned when the weapons were designed. The National Nuclear Security Administration (NNSA) was established in 2000 to carry out the national security responsibilities of the Department of Energy, including maintenance of a safe, secure, and reliable stockpile of nuclear weapons and associated materials capabilities and technologies.
The NNSA’s Science-Based Stockpile Stewardship Program was established to develop new means of assessing the performance of nuclear weapon systems, predict their safety and reliability, and certify their functionality. The program must not only fulfill its responsibilities without nuclear testing, but must also address constraints on non-nuclear testing, the downsizing of production capability, and the cessation of developing new weapon systems to replace existing weapons. Further complicating matters, weapon components are exceeding their design lifetimes, and manufacturing issues and environmental concerns will force changes in fabrication processes and materials of weapon components.
How ASC Supports the Science-based Stockpile Stewardship Program
ASC serves the Science-Based Stockpile Stewardship Program (SBSS) in the following ways: