(IDAHO FALLS, Idaho) – The Department of Energy’s MARVEL microreactor project recently cleared more milestones as Idaho researchers prepare the reactor for initial startup tests this winter.
The microreactor’s primary coolant system, or PCS, arrived at the Idaho National Laboratory in mid-September, completing fabrication and delivery of a key component and pushing the microreactor a step closer to achieving criticality — a stable nuclear chain reaction that’s an important step toward full operation.
MARVEL, short for Microreactor Applications Research Validation and Evaluation, is led by INL for the Department of Energy. The coolant system arrived at INL’s Transient Reactor Test Facility, where it will now be integrated with the reactor’s other systems before it achieves criticality, which is anticipated to occur in December.
During full-power operations, the PCS carries heat away from the reactor core using a sodium-potassium alloy as a coolant. The alloy remains liquid at room temperature and efficiently absorbs and transfers heat at high reactor temperatures without requiring pressurization.
Just before the PCS arrived, DOE’s Idaho Operations Office approved MARVEL’s final documented safety analysis — a key safety document authorizing a dry criticality configuration that will generate data intended to serve as a national benchmark for reactor physics. Dry criticality is the critical condition achieved with near-zero power generation, so no coolant is needed or present.
“We’re ecstatic to not only have our PCS fabricated, but also to get this important approval from DOE, which allows us to move toward MARVEL’s initial criticality,” said Abdalla Abou-Jaoude, the MARVEL microreactor lead. “Based on DOE guidance, we are also very open to sharing this approved document with key stakeholders in the hopes that it can serve as a template for industry.”
“The documented safety analysis represents years of rigorous engineering and safety analysis work by our team,” said Doug Gerstner, nuclear safety engineer at INL. “This approval validates the risk-informed methodology we developed, and we’re confident it provides a strong foundation for MARVEL’s path to criticality.”
The approval is also in line with broader DOE goals under recent executive orders to accelerate the review and deployment of advanced reactors. Advanced reactors are seen as key to strengthening energy security, meeting growing electricity demand and maintaining U.S. leadership in nuclear innovation.
“This milestone is a testament to the hard work and dedication of the MARVEL team, INL leadership and DOE,” said John Jackson, national technical director for the DOE Microreactor Program.
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