ALEXANDRIA, VA — The Lawrence Livermore National Laboratory was set to fire the first test in its Nimble series of subcritical experiments in the late summer, a senior lab official said here Wednesday.
“The first one [called Nob Hill] is scheduled for August of this year, the next one [Twin Peaks] will be hopefully a few months later and actually Mission Hills … is a few years out,” Bradley Wallin principal associate director for weapons and complex integration at the Lawrence Livermore National Laboratory, said here at the Exchange Monitor’s annual Nuclear Deterrence Summit.
The tests share names with California neighborhoods.
“I think they’re intended to be locations in the Bay Area,” Wallin said. The teams working on each project choose the project’s name, he told the Monitor on the sidelines of the annual conference. Livermore’s main campus is about 50 miles east by road from San Francisco.
In subcritical tests, nuclear-weapon labs essentially blow up small pieces of plutonium inside of a steel sphere in the U1a underground facility at the Nevada National Security Site. These detonations bring the plutonium to the threshold of nuclear criticality, the U.S. says, allowing labs to physically test parts of existing weapons without resorting to nuclear-explosive tests. The U.S. has not tested a weapon at full yield since 1992.
Livermore is responsible for maintaining the W80 air-launched cruise missile warhead, the W87 intercontinental ballistic-missile warhead and the B83 megaton-capable gravity bomb. The Department of Energy’s National Nuclear Security Administration (NNSA), which owns the U.S. nuclear-weapons labs, is dismantling some of the B83 stockpile.
The three experiments in the Nimble series were supposed to get started in 2022, but various problems, including with the test facility at the Nevada National Security Site, held things up. Last autumn, because of safety concerns, Nevada site management banned subcritical payloads from the hoist used to lower things into the U1a complex.
The prohibition on putting subcritical experiments on the hoist should still be lifted by March 30, Garrett Harencak, president and CEO of the Honeywell-led Nevada site prime contractor Mission Support and Test Services, told the Monitor here on Wednesday.
