DOE approves key safety milestone for INL’s MARVEL microreactor

The following is a news release from the Idaho National Laboratory:

IDAHO FALLS, Idaho — The U.S. Department of Energy’s Idaho Operations Office has approved a key safety document for the MARVEL microreactor at Idaho National Laboratory. The approved document, called a Preliminary Documented Safety Analysis (PDSA), marks a major milestone toward building and operating the microreactor for research, development and end-user demonstrations.

MARVEL, the Microreactor Applications Research Validation and Evaluation project, is a sodium-potassium-cooled microreactor developed at INL to produce 85-100 kilowatts of thermal energy and approximately 20 kW of electricity.

The PDSA outlines a dry initial criticality configuration, a near zero-power experiment that will generate essential data on reactor physics behavior. This configuration is a foundational step on the pathway to full power operation.

The approval reflects the culmination of extensive safety calculations and engineering analyses that define the safety basis for MARVEL’s initial criticality. The PDSA affirms that the reactor can operate safely under this configuration and paves the way for final safety documentation and full assembly of the reactor.

“This is more than just a regulatory requirement — it’s a blueprint for the future of advanced nuclear,” said INL’s Abdalla Abou-Jaoude, MARVEL microreactor lead. “By receiving approval for our safety documentation, we are now able to share this template with developers to learn from our process and streamline their own timelines.”

“This is a pivotal moment,” added John Jackson, national technical director for the DOE Office of Nuclear Energy’s Microreactor Program. “We’re proud to play a leading role in helping to make microreactors commercially available.”

The approved PDSA builds on a 2024 version and incorporates updated modeling, lessons learned and a risk-informed methodology — an approach that uses risk analysis to guide design decisions and enhance safety. MARVEL’s approach has already influenced other DOE-authorized reactor projects such as Pele, the Molten Chloride Reactor Experiment and the Versatile Autonomous Lightweight Kilowatt-class Reactor Experiment, commonly known as VALKRE. 

Researchers will conduct the dry criticality experiment at INL’s Transient Reactor Test Facility, a DOE-authorized research facility that supports a variety of reactor experiments. The next phase includes engagement with DOE-Idaho and project stakeholders to finalize the safety basis for full reactor assembly and fuel loading. This phased approach is designed to identify and address potential issues earlier in development.

The MARVEL team encourages the public and stakeholders to follow progress via INL’s social media channels and the MARVEL project webpage.