NAC International Supports the First Microreactor Criticality Demonstration under DOE Pilot Program
NAC supported Antares’ historical achievement in reaching initial criticality with its Mark-0 microreactor by successfully transporting BWXT-manufactured TRi-structural ISOtropic (TRISO) nuclear fuel compacts to the Idaho National Laboratory (INL).
NAC provided its OPTIMUS®-L packaging for safe shipment of TRISO fuel compacts.
On June 4, 2026, Antares announced that its Mark-0 microreactor was brought to criticality at INL in a demonstration under the U.S. Department of Energy Reactor Pilot Program, the first advanced reactor in the program to complete this milestone. The TRISO nuclear fuel that powered the criticality demonstration was manufactured by BWXT, a leading fuel producer with a long history of TRISO fuel development. Antares based its Mark-0 reactor fuel specification on the TRISO fuel compacts that BWXT delivered for Project Pele, utilizing NAC's OPTIMUS®-L packaging.
NAC provided packaging preparation and technical support for the loading and unloading of the TRISO fuel compacts for Antares and delivery to INL using its fleet of OPTIMUS®-L packagings. The OPTIMUS®-L packaging was designed by NAC and is certified by the U.S. Nuclear Regulatory Commission to transport a wide range of radioactive materials, including TRISO fuel compacts.
“We congratulate Antares on completing the first-ever fueled criticality demonstration of their microreactor, a remarkable achievement,” said Kent Cole, NAC President and CEO. “NAC is proud to collaborate with this team to support the validation and advancement of a new era of nuclear energy using advanced reactors.”
With more than 3,900 shipments of nuclear fuel and radioactive materials completed in 33 years, NAC is an experienced operator as well as an innovator in developing transport packagings that provide solutions for the nuclear industry.
About NAC International
NAC International is a leading provider of nuclear fuel cycle services and technologies, specializing in the design, licensing, and application of spent nuclear fuel storage and transportation systems. Headquartered in Peachtree Corners, Georgia, NAC serves utilities, research reactors, government agencies, and international clients across the full back-end nuclear fuel cycle. For more information, visit www.nacintl.com.
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