Stockpile stewardship

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.

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.

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.