Lawrence Livermore National Laboratory’s Nimble series of subcritical experiments in Nevada should wrap up in fiscal year 2024, about a year later than the California nuclear-weapons lab once planned.
The Nimble series “is scheduled to be complete later in FY23 & early FY24” a lab spokesperson wrote in an email on Monday, referring to government fiscal years 2023, which began Oct. 1, and fiscal year 2024, which begins Oct. 1, 2023.
That’s about a year behind the schedule that a lab official laid out in February at the Exchange Monitor’s annual Nuclear Deterrence Summit, when the first experiment in the Nimble series, Twin Peaks, was on the slate for the spring.
The Nevada National Security Site’s underground subcritical testing laboratory, the U1a Complex, had been in cold standby for much of the year, according to a report from the the Defense Nuclear Facilities Safety Board.
Also, the hoist used to lower subcritical experiments into the U1a lab was taken out of service after heavy monsoon-season rains in August and September by the site’s Honeywell-led site contractor, Mission Support and Test Services, the defense board said.
A spokesperson for the Nevada test site, reached Monday, did not have an immediate comment about the status of the U1a hoist.
Subcritical experiments involve the explosive compression, inside a heavy steel containment sphere, of small quantities of plutonium. These detonations produce no nuclear yield, the U.S. says, but allows scientists to observe — using high-speed x-ray cameras — the behavior of fissile material under conditions that resemble the early stages of a nuclear explosion.
Analyzing those images helps weapons designers at Livermore and Los Alamos understand, without resorting to full-up, Cold War-style, nuclear-explosive tests, how nuclear-weapon components are aging and whether they have retained their design destructive capabilities.
