How the U.S. Maintains Its Nuclear Arsenal—Without Explosive Testing

The U.S. ended explosive nuclear testing in the 1990s, but that does not mean we are unprepared. I previously served as Chief Scientist for the National Nuclear Security Administration and here’s how the U.S. ensures proper stewardship of its nuclear stockpile.

No explosive nuclear tests since 1992  

In its place, the U.S. uses a science-based program that checks the health of the stockpile continuously and reports out every year to the President.

Annual “health check” of the arsenal

Each year’s assessment includes its safety, security, and effectiveness. It’s built on world-class expertise, experiments, continuous surveillance of parts, the most advanced computer simulations, and rigorous engineering reviews.

Smarter than the test era

Modern tools let the U.S. simulate scenarios we could never safely test, explore “what ifs,” and study how systems might fail—so we can prevent problems before they matter. This goes far beyond what was possible when we conducted explosive tests. Modern science beats old tests.

• Past nuclear tests used specialized, instrumented test devices, not the exact deployed weapons. That limited what we could learn.
• Tests were usually designed for success, not to map out the edges of performance or potential failure modes.
• A test could tell us if a system worked but offered little about how or why. Today’s diagnostics and supercomputer models reveal remarkable details, giving leaders far more options and understanding.

Staying ahead of aging and change

Materials age and manufacturing methods evolve. Today’s science-based approach tracks aging, spots issues early, and guides safe fixes, all while meeting modern security requirements—without returning to explosive testing.

What this means for Americans

• A secure and effective nuclear stockpile maintained by science, not explosions.
• Better insight than ever into how our own systems behave—and how others’ systems might behave—supporting sound decisions in a crisis.
• Confidence we do not need to resume explosive nuclear testing to keep the system reliable.

Bottom line: Thanks to sustained investments in facilities, computing, diagnostics, and methods, the United States understands its nuclear weapons better today— ensuring their reliability more than explosive testing ever did.