Antares Nuclear Signs Second TRISO Fuel Deal With BWXT Ahead of 2027 Mark-1 Startup
Antares Nuclear has signed its second fuel fabrication agreement in three months, securing TRISO fuel from BWX Technologies (BWXT) for its first electricity-producing microreactor, Mark-1, as the California startup moves from criticality tests toward powering actual hardware.
The multi-year agreement, announced October 27, covers an initial one metric ton of uranium (MTU) with provisions to scale up as Antares’ deployment needs grow, and runs through the end of the decade. BWXT will fabricate the high-assay low-enriched uranium (HALEU) TRISO fuel at its Lynchburg, Virginia facility, on the same production line that supplied fuel for Antares’ Mark-0 demonstration reactor and for the US Department of War’s Project Pele transportable microreactor. Specific delivery quantities and schedules will be set through later task orders, and neither company disclosed a contract value.
A second supplier, not a first
BWXT is now Antares’ second TRISO fabricator. In August, the company signed a binding agreement with Standard Nuclear covering 1 to 8 MTU of fuel, with deliveries running through 2035. Antares has also lined up HALEU supply agreements with Centrus Energy, signed in September, as well as arrangements with Urenco and General Matter, spreading its fuel supply chain across multiple vendors rather than depending on a single source as it scales toward commercial deployment. “As demand grows across the advanced reactor sector, BWXT is prepared to scale,” said Joe Miller, president of BWXT Government Operations, adding that the company has “refined the processes for high-performance TRISO fuel.”
From criticality to electricity
The BWXT deal lands just after a formal regulatory step for Mark-1, the reactor the new fuel is meant to power. The US Department of Energy approved Mark-1’s Nuclear Safety Design Agreement on October 23, the first stage in its safety authorization process rather than clearance to operate. Antares plans to run Mark-1 at Idaho National Laboratory in 2027 for a six-month campaign at full electrical power, following the same authorization path used for Mark-0, which reached zero-power criticality on June 4 this year using BWXT fuel after clearing its own Nuclear Safety Design Agreement, Preliminary Documented Safety Analysis and Documented Safety Analysis between October 2025 and April 2026. “We achieved criticality with BWXT fuel, and it’s what will power our electricity-producing reactor, Mark-1, in 2027,” said Antares chief executive Jordan Bramble, who has said Mark-1 “isn’t a scaled-down, stand-in test rig.”
Betting on defense customers first
Antares’ commercial model runs through defense and federal demonstration programs rather than utility customers, at least for now. Its R1 microreactor, rated between 100 kWe and 1 MWe with a refueling interval of six or more years, was selected in August for the US Army’s $2.2 billion Janus Program, under which Antares plans three R1 units at Fort Bragg, North Carolina, with initial deployments beginning in 2028. The company was also picked in April for the Air Force’s Advanced Nuclear Power for Installations program, for a prototype at Joint Base San Antonio, Texas, and won a $161 million Space Force Strategic Breakthrough award in September to advance an R1-S variant for space applications.
That pipeline sits inside a broader push by Washington to get advanced reactors through demonstration faster: the Nuclear Regulatory Commission finalized a rule on October 22, published in the Federal Register on October 26, that lets commercial reactor applicants reference safety work already done under DOE- and military-authorized demonstrations. Antares has not announced plans to seek NRC licensing for Mark-1 itself, and its near-term path runs through DOE and military authorization rather than the civilian regulator. The approach mirrors how established nuclear vendors sequence fuel delivery against construction and commissioning milestones, even as Antares compresses that timeline from years to months by building on an existing demonstration reactor rather than a new plant.
Sources: POWER Magazine, “Antares Secures BWXT Fuel Agreement, Advances DOE Review for Electricity-Producing Mark-1,” by Sonal C. Patel, 27 October 2026, https://www.powermag.com/antares-secures-bwxt-fuel-agreement-advances-doe-review-for-electricity-producing-mark-1/ (primary account of the fuel deal, Mark-0/Mark-1 timeline, Army/Air Force/Space Force program details, company quotes); World Nuclear News, “Antares, BWXT in TRISO fuel procurement deal,” 29 October 2026, https://world-nuclear-news.org/articles/antares-bwxt-in-triso-procurement-deal (independent confirmation of deal terms and timeline).
Illustrative image. Photo: Christian David, CC BY-SA 4.0, via Wikimedia Commons — source
