Inside an underground facility where the U.S. tests nuclear weapons

By Regina G. Barber,

Rachel Carlson, Berly McCoy

Published February 11, 2025 at 9:21 AM EST

A tunnel in the underground PULSE laboratory in Nevada, where scientists conduct experiments to test nuclear weapons without detonating them.

The U.S. tested nuclear weapons until the early 1990s. Since then, scientists have been using supercomputers and experiments to simulate nuclear test detonations, without detonating any nukes. But there are signs the world's nuclear powers may be readying to test again: Russia, China and the U.S. are all upgrading their nuclear test sites.

NPR's science correspondent Geoff Brumfiel was among a small group of journalists allowed to tour an underground laboratory where this research happens.

Read more of science correspondent Geoff Brumfiel's reporting here.

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Today's episode was produced by Rachel Carlson. It was edited by Berly McCoy. Tyler Jones and Geoff Brumfiel checked the facts. Jimmy Keeley was the audio engineer.