Holtec advances component fabrication for SMR-300 reactor testing facility at Idaho National Laboratory

Holtec announced in September 2026 that it’s moving forward with component fabrication for HI-TEST, a dedicated reactor testing facility under development at Idaho National Laboratory. The facility exists for one specific reason: putting the SMR-300 pressurized water reactor through its paces—stress-testing performance margins and accident scenarios before the thing ever goes commercial.

Holtec moves forward with HI-TEST facility at INL

That September 2026 announcement isn’t just a press release. It marks a real shift from design work to physical construction. Hardware is being built, components assembled, all for a facility with a single job: push the SMR-300 hard, under controlled conditions, before it powers a single home or business.

HI-TEST—Holtec Integrated Test facility—was designed specifically around the SMR-300 pressurized water reactor program. It’s not generic research infrastructure repurposed for the job. The facility is built around the reactor’s actual architecture and operating conditions, and that distinction matters. Generic test rigs require workarounds, and workarounds introduce variables that muddy results.

Steam generators are critical components in pressurized water reactors—they transfer heat from the reactor coolant to the secondary loop that drives the turbines.

Getting into fabrication is a concrete milestone for Holtec. Reactor development programs can spend years in design review and regulatory back-and-forth before anything physical happens. Crossing into fabrication means the SMR-300 program has cleared enough internal and regulatory hurdles to justify serious capital investment in dedicated infrastructure.

Why Holtec is building a dedicated test facility

The core job of HI-TEST is replication. Test loops simulate accident scenarios—the low-probability, high-consequence events that nuclear regulators require developers to analyze in exhaustive detail. By physically recreating those conditions in a controlled environment, Holtec can generate empirical data instead of relying solely on computational models.

Steam generators are critical components in pressurized water reactors—they transfer heat from the reactor coolant to the secondary loop that drives the turbines. How they perform under both normal and abnormal conditions must be modeled carefully to validate the SMR-300’s overall thermal-hydraulic design. That makes steam generator behavior one of HI-TEST’s key targets.

A purpose-built facility offers something existing infrastructure can’t easily match: repeatability. Demonstrating that a safety system performs consistently across dozens of simulated scenarios requires tight control over variables. Retrofitting existing test rigs to a new reactor’s specs introduces uncertainty that a dedicated facility simply cuts out.

Testing at INL also lets Holtec quantify performance margins—the headroom between normal operating conditions and the thresholds where safety systems kick in. Wider margins generally support a stronger licensing case and can open the door to operational improvements later.

Planned outcomes: Safety validation and power uprating

The data coming out of HI-TEST isn’t just for internal engineering. It feeds directly into regulatory submissions. The Nuclear Regulatory Commission requires extensive safety analysis as part of the design certification process, and empirical test data carries real weight alongside computational simulations. HI-TEST is set up to supply that evidence base for the SMR-300’s licensing dossier.

Accident scenario replication is especially important here. The NRC’s licensing framework requires developers to demonstrate how a reactor responds to a defined set of design-basis accidents—things like loss-of-coolant accidents or feedwater system failures. Physical test data from HI-TEST could strengthen Holtec’s case that the SMR-300 behaves exactly as modeled under those conditions.

Holtec has also said HI-TEST is meant to support future power uprating of SMR-300 units. Power uprating—increasing a reactor’s licensed thermal output above its original design point—is a well-established practice in the existing nuclear fleet. You need to demonstrate sufficient safety margins at the original power level before pursuing higher output. Building that capability into the test program from the start suggests Holtec is already thinking about commercial optimization, not just getting the first units online.

Background: Holtec’s SMR-300 and the role of INL

The SMR-300 is a small modular reactor built on proven pressurized water reactor technology, designed for scalable deployment—units built in factories, assembled on-site, with shorter construction timelines and lower upfront capital costs than large conventional nuclear plants. The “300” refers to its approximate electrical output in megawatts, placing it in the mid-range of the SMR category.

Idaho National Laboratory is a natural fit for HI-TEST. INL is the United States’ primary nuclear energy research facility, with decades of experience hosting reactor testing programs and the physical infrastructure to support complex nuclear experiments. Its regulatory familiarity and existing safety frameworks make it a practical choice for developers building new test capabilities from scratch.

Holtec International is one of several companies pursuing NRC design certification for an SMR. Others include NuScale, which received design certification for its VOYGR reactor in 2022, along with a range of developers working on both light-water and advanced reactor concepts. The broader SMR sector is betting that smaller, factory-built reactors can sidestep the cost overruns and construction delays that have plagued large nuclear projects for decades.

Built to evaluate the pressurized water reactor

HI-TEST is a dedicated reactor testing facility under construction at Idaho National Laboratory, built specifically to evaluate the SMR-300 pressurized water reactor. Holtec confirmed in September 2026 that component fabrication is progressing. The facility will use test loops to replicate accident scenarios and model steam generator behavior, generating empirical safety data to support NRC licensing submissions. It’s also designed to establish the performance margin data needed for future power uprating of deployed SMR-300 units—a meaningful step from design-phase work to physical development in Holtec’s SMR program.

Kelly Lippke

Kelly is an experienced writer with 15 years of experience exploring the big stories that shape our world, from tech breakthroughs and space exploration to climate, energy, and the fascinating quirks of science. She has a talent for turning complex ideas into sharp, memorable insights that stay with readers long after they’ve finished reading.