A welding machine reportedly caught fire in April during welding activities in the Principal Underground Laboratory for Subcritical Experimentation (PULSE) at Nevada National Security Site.
The fire was reported in a June 6 report by the Defense Nuclear Facilities Safety Board (DNFSB). According to the report, a welding machine caught fire and the fire watch immediately extinguished it. Nevada National Security Site’s (NNSS) prime contractor Mission Support and Test Services (MSTS) then removed the machine for inspection.
MSTS has since suspended welding activities at PULSE to remove and inspect all the welding machines. As of the date of the report, the safety investigation is still ongoing.
PULSE, formerly named the U1a complex, is a facility nearly 1,000 feet underground at the NNSS used to conduct subcritical plutonium experiments. The aim of PULSE is to support nuclear stockpile stewardship without testing any nuclear weapons.
Senior officials at NNSS told the Exchange Monitor on a media trip in December that the next subcritical experiment at PULSE was slated for spring 2025, but senior officials at the National Nuclear Security Administration refused to comment on whether the experiment took place or whether it was successful.