Idaho Lab Received MARVEL Microreactor Coolant System
The primary coolant system arrived at the Transient Reactor Test Facility in September to prepare for future testing.
Updated on Oct. 12, 2026 in Nuclear
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In mid-September 2026, the Idaho National Laboratory received the primary coolant system for the MARVEL microreactor. Engineers have since begun integrating the system into the reactor at the Transient Reactor Test Facility.
Why it matters
This project aims to explore microreactor operation and collect critical data for the development of advanced reactor designs. The sodium-potassium alloy coolant system is essential for transferring heat away from the reactor core during operation.
The system utilizes a sodium-potassium alloy that remains liquid at room temperature for thermal management. Researchers will perform dry criticality configurations to study physics without power generation or coolant prior to full thermal operation.
The players
Idaho National Laboratory
This facility is a leading center for nuclear energy research and development in the United States.
U.S. Department of Energy
This federal agency is responsible for the energy policy and nuclear safety programs of the United States government.
The details
Engineers are currently integrating the coolant components with the reactor core at the Transient Reactor Test Facility. The U.S. Department of Energy's Idaho Operations Office has already approved the final safety analysis required for these technical configurations.
Timeline
The primary coolant system arrived at the testing facility in mid-September 2026.
Initial criticality testing is expected to begin in December 2026.
The Big Picture
This development follows the trajectory established by the U.S. Department of Energy's microreactor development program. Integrating this cooling technology marks a key technical milestone that advances the national capability for future reactor design.
Advancements in microreactor technology could eventually lead to the development of more efficient and modular energy sources for grid or off-grid power. Successful integration of these cooling systems helps refine the safety and operational protocols necessary for future commercialization.
The takeaway
The successful integration of the MARVEL cooling system demonstrates the steady progress of U.S. nuclear research initiatives. Residents and stakeholders can monitor future announcements regarding the upcoming criticality testing phase for additional updates.
What happens next
The laboratory expects to commence initial criticality testing of the MARVEL microreactor in December 2026.
Further reading
Learn more about local efforts by visiting the Idaho Nuclear section.
Source note: This article includes information reported by Etownian.
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