US carries out underground chemical explosive test in Nevada
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The United States conducted a non-nuclear underground chemical explosive experiment at the Nevada National Security Site on Wednesday to strengthen its ability to detect low-yield nuclear blasts.
The National Nuclear Security Administration (NNSA) successfully carried out the subsurface test in the P Tunnel in Area 12 using chemical high-explosives and radiotracers.
Officials said the data will validate scientific models and refine algorithms critical to US nuclear explosion detection efforts.
Researchers collected measurements with a suite of advanced sensors, including accelerometers, seismometers, infrasound sensors, electromagnetic sensors, chemical and radiotracer samplers, and meteorological sensors.
The experiment focused especially on improving detection of “decoupled” explosions.
In a conventional coupled underground test, a device sits in close contact with the rock so much of the shockwave reaches sensors.
In a decoupled test, the device detonates inside a large underground chamber, muffling the seismic signature and making a large blast appear smaller—much as a stealth aircraft looks smaller on radar.
US officials said this is the type of test they determined China conducted in June 2020 at its Lop Nur nuclear test site.
Washington had accused Beijing earlier in 2026 of carrying out the secret low-yield test while calling for a broader arms-control treaty.
China rejected the allegation as “entirely unfounded” and an attempt “to fabricate excuses for resuming” US nuclear testing.
NNSA Administrator Brandon Williams emphasized the strategic value of the work: “It takes nuclear expertise to detect nuclear activities and experiments like these ensure America remains unmatched in detection. The Trump Administration has made it clear that the United States will lead from a position of strength. You cannot evade American innovation. With this experiment, we are sending a clear message: under this administration, America will never be outmatched.”
The non-nuclear experiment forms part of ongoing efforts to close capability gaps in monitoring low-yield and concealed foreign tests without using nuclear material.
By gathering multi-physics data from the chemical blast, scientists aim to better characterize the signatures of underground explosions and enhance global nuclear nonproliferation monitoring.
