The USreleases an unclassified version of the Nuclear Posture Review every few years, which provides an overview of the role of nuclear weapons in its security strategy.
The most recent report, released in October last year, said that Washington would only consider using nuclear weapons in “extreme circumstances.” However, it also stated that the US does not adopt a “no first use policy” because it would result in an “unacceptable level of risk” to its security.
The US conducted its last underground test in 1992, but Lewis said the US has long been keeping itself in a state of readiness for a nuclear test, ready to react if one of its rivals moves first.
“The United States has a policy of being prepared to conduct a nuclear test on relatively short notice, about six months,” he said.
The commercial satellite imagery, taken above the nuclear test site in Nevada, officially known as the Nevada National Security Site, shows that an underground facility – the U1a complex – was expanded greatly between 2018 and 2023.
The National Security Administration (NNSA), an arm of the US Department of Energy that oversees the site, says the laboratory is for conducting “subcritical” nuclear experiments, a longstanding practice meant to ensure the reliability of weapons in the current stockpile without full-scale testing.
“In subcritical experiments, chemical high explosives generate high pressures, which are applied to nuclear weapon materials, such as plutonium. The configuration and quantities of explosives and nuclear materials are such that no nuclear explosion will occur,” the NNSA’s website says.
In response to CNN’s request for comment, a spokesperson from the NNSA confirmed it has been “recapitalizing infrastructure and scientific capabilities” at the Nevada test site, which includes procuring new advanced sources and detectors, developing reactivity measurement technology, and continuing tunneling activity.
“(This) will provide modern diagnostic capabilities and data to help maintain the safety and performance of the US nuclear stockpile without further underground nuclear explosive testing,” the spokesman added.