Stockpile stewardship refers to the United States program of reliability testing, viability, and the maintenance of its nuclear weapons without the use of nuclear testing.
Because no new nuclear weapons have been developed by the United States since 1992, [1] even its youngest weapons are at least 32 years old (as of 2025). Aging weapons can fail or act unpredictably in a number of ways: the high explosives that compress their fissile material can chemically degrade, their electronic components can suffer from decay, their radioactive plutonium/uranium cores are potentially unreliable, and the isotopes used by thermonuclear weapons may be chemically unstable as well. [2]
Since the United States has also not tested nuclear weapons since 1992, [3] this leaves the task of its stockpile maintenance resting on the use of simulations (using non-nuclear explosives tests and supercomputers, among other methods) and applications of scientific knowledge about physics and chemistry to the specific problems of weapons aging (the latter method is what is meant when various agencies refer to their work as "science-based"). It also involves the manufacture of additional plutonium "pits" to replace ones of unknown quality, and finding other methods to increase the lifespan of existing warheads and maintain a credible nuclear deterrent.
Most work for stockpile stewardship is undertaken at United States Department of Energy national laboratories, mostly at Los Alamos National Laboratory (LANL), Sandia National Laboratories (SNL), Lawrence Livermore National Laboratory (LLNL), the Nevada Test Site (NTS), and the Department of Energy's other productions facilities, which employ around 27,500 personnel and cost billions of dollars per year to operate.
The Science-based Stockpile Stewardship is a program managed and oversee by the United States's Department of Energy (DoE) to ensure that the nuclear weapons capabilities of the United States are not eroded as the nuclear weapons age. [4] It costs more than $4 billion annually [5] to test the components of the nuclear weapons and build advanced science facilities, such as the National Ignition Facility (NIF) at the Livermore (California) and the Z-Pulsed Power Facility at the Sandia (New Mexico). Such facilities have been deemed necessary under the program since President Bill Clinton signed the Comprehensive Test Ban Treaty (CTBT) in 1996, [5] [6] but the United States Senate never ratified the CTBT.
Later, President Barack Obama initiated a wide range and a broad effort to modernize the United States nuclear weapons program, which the Congressional Budget Office estimates will require approximately $494 billion to complete. [7]
The stockpile stewardship program is supported by the following experimental facilities: [8]
The data produced by the experiments carried out in these facilities is used in combination with the Advanced Simulation and Computing Program. [8]
Moreover, unlike other nations, the U.S. has not conducted a nuclear-weapons test since 1992; it has not designed a new warhead since the 1980s or built one since the 1990s. It has reduced its nuclear-weapons stockpile by 75% since the end of the Cold War and 90% since the height of the Cold War.
President Clinton signed a treaty today that would ban all nuclear weapons testing and called on world leaders to take further steps to limit weapons of mass destruction.