The Nevada National Security Site plans to allow subcritical experiment packages back onto the hoist leading to the U1a underground experimental complex in the spring, a site spokesperson said Wednesday.
After an active desert monsoon season in August and September, the Nevada site discovered some muck at the bottom of the entrance shaft to the U1a complex, where nuclear-weapon design labs conduct the subcritical, explosive plutonium experiments required to assess the effectiveness of U.S. nuclear weapons.
The muck had accumulated to such a height in the U1a hoist sump that site personnel deemed it unsafe to transport subcritical experiment packages using the hoist; the height to which the muck had risen meant that, in an emergency, there might not be enough stopping distance to prevent damage to one of these unique experiments, according to a report about the incident by federal Defense Nuclear Facilities Safety Board.
So, on Sept. 22, Nevada site prime Mission Support and Test Services, a Honeywell-led team, prohibited transport of subcritical experiment packages using the hoist, a spokesperson for the prime wrote in an email on Wednesday. The site planned to lift that prohibition on March 30, according to the spokesperson.
The U1a complex has been in cold standby for much of the year, according to the Defense Nuclear Facilities Safety Board.
Meanwhile, the Lawrence Livermore National Laboratory is waiting to continue with its Nimble series of subcritical experiments in Nevada. That series was scheduled to wrap up early in government fiscal year 2024, which begins Oct. 1, a lab spokesperson said Monday.
