Lawrence Livermore National Laboratory (LLNL) has completed delivery of the first 220 line-replaceable units (LRUs) to the Integrated Test Stand (ITS) at Nevada National Security Sites (NNSS), as well as the first 100 LRUs to be used at NNSS's underground facility, the Principal Underground Laboratory for Subcritical Experimentation (PULSE). The two major hardware delivery milestones mark key progress toward the start of integrated testing for Scorpius, the nation's next-generation accelerator. The deliveries provide the pulsed-power hardware needed to support full-scale system evaluation at ITS ahead of installation and commissioning at PULSE.
"These achievements represent the completion of our first full production sets of LRUs and set the stage for the next major phase, integrated testing," said Andréa Schmidt, LLNL's site-specific team lead for the Scorpius program. "It's both a significant technical step forward and a major coordination effort across multiple national laboratories and partners."
A one-of-a-kind diagnostic
Designed and built by multiple national laboratories, Scorpius is advancing experimental capabilities for the nation's stockpile stewardship and modernization programs. The linear-induction accelerator, which will be more than 100 meters long, will capture multiple, precisely timed X-ray images of subcritical experiments using plutonium, allowing scientists to study how materials behave during the late stages of a nuclear implosion.
Each of the accelerator's LRUs delivers short, powerful bursts of energy to drive the electron beam that creates those X-rays. The technology uses LLNL's innovative solid-state pulsed-power design, which provides unprecedented control over accelerator pulse shape, width and spacing compared to existing accelerators. The units are modular, meaning they can be easily swapped or replaced, improving both flexibility and reliability during operations.
Scorpius will ultimately include nearly 1,000 LRUs when it is completed at PULSE. The first 220 units delivered will power the Integrated Test Stand (ITS), the accelerator's first system-level testbed, where teams will assemble, commission and test the accelerator's injector, a major subsystem designed and built at Sandia National Laboratories. ITS tests will also include Scorpius's first two accelerator modules to confirm performance before moving the system underground and completing the accelerator build.
Deliveries for the first 220 LRUs and subsequent 100 LRUs concluded in September 2025 and January 2026, respectively, after years of design, prototyping, launching a new production line and engaging in continuous quality verification with vendors.
"We have a very rigorous quality process," said Kristen Rosier-Miyares, a mechanical engineer who leads LRU integration for the project. "Our team visited the vendors multiple times throughout the build to see their processes firsthand and ensure consistency at every stage. It was very collaborative with lots of open communication and problem-solving on both sides."
Each LRU is function-tested and mechanically inspected to verify that all components meet strict performance standards, a process refined through continuous feedback from assembly teams and technical experts.
Procurement staff described the milestone as the result of close coordination among dozens of subcontractors and suppliers, many of them small businesses. Procurement analysts, engineers and vendors worked closely to manage the flow and quality of millions of components and keep production on schedule. "It took an enormous amount of coordination to keep components flowing and production on track," said Angela Merritt, the project's lead procurement analyst. "Technical representatives, contract analysts and our suppliers were fully partnered from start to finish."
The procurements team recently awarded the final LRU contract for ASD Scorpius, and production will continue into early 2027.
Although the LRUs were assembled by vendors, Livermore engineers and technicians played key roles in supporting production by sharing expertise from earlier prototype builds and assisting with troubleshooting when issues arose during assembly or testing. For many on the team, the milestones carry a shared sense of craftsmanship and accomplishment, reflecting both the precision of the work and the teamwork built over several years of iteration and problem-solving.
Simultaneous with integration vendor production of LRUs, LLNL completed another major in-house deliverable of the middleware needed to serve the ITS integration effort, built at the Laboratory. Middleware serves as the interface between clusters of LRUs and the rest of the accelerator control system, synchronizing their timing and energy output.
"The middleware was a huge in-house effort that took a dedicated team to design, build and deliver alongside the production LRUs," said Mitchell Lane, lead installation engineer of middleware hardware.
National partnership
The Scorpius project is a collaboration with Los Alamos National Laboratory, Sandia National Laboratories, NNSS and the National Nuclear Security Administration. LLNL leads the pulsed-power effort. As the different subsystems start to come together, LLNL will also have major contributions to system integration.
Schmidt said the next phase of testing at ITS will reflect the strength of the project's collaboration. "This effort brings together experts from across the complex, all focused on advancing the same goal," she said. "Livermore, Sandia, Los Alamos and NNSS are working side by side, solving problems together, and moving this key capability forward."
With production hardware in place and middleware delivered, the Scorpius team is continuing to support production, preparing for integrated testing and continuing steady progress toward operation.
