Antares, Last Energy, and Radiant hit DOE authorization milestones

The month of October saw three of the original Reactor Pilot Program companies hit a handful of milestones as each pursues Department of Energy authorization for the operation of various reactor projects. Both Last Energy and Radiant earned documented safety analyses (DSAs) for their first reactors, and Antares earned its nuclear safety design agreement (NSDA) for its second reactor.

Approval breakdown: Companies working toward DOE authorization for the operation of their test and demonstration reactors through either the Reactor Pilot Program or the Nuclear Energy Launch Pad must pass through five milestones:

1. The OTA, or other transaction agreement, is the first step, marking the formal entrance into partnership between the DOE and a company.
2. The NSDA is the second step. It is generally described as the foundational safety framework on which future development rests.
3. The PDSA, or preliminary documented safety analysis, comes next. One participant, Oklo, has previously characterized this stage as a detailed review of a reactor's design, covering "hazard analysis, accident analysis, safety controls, and design commitments."
4. The DSA is the penultimate step. Last Energy has described this stage as "the final and most comprehensive safety analysis in the DOE authorization process," documenting how a company's reactor and facility will operate.
5. The readiness review is the final stage of DOE authorization. Radiant has said this last step is an assessment of whether the reactor and the team responsible for operating it are prepared to begin operations.

Antares milestone: On October 23, Antares announced that the DOE had approved the NSDA for Mark-1, which the company calls its first "electricity-producing reactor." Mark-1 builds on the lessons learned by Mark-0, the company's first reactor, which reached zero-power criticality at Idaho National Laboratory in June. Antares ultimately is pursuing a 100 kWe-1 MWe reactor design that uses TRISO fuel, sodium heat pipes for cooling, and a nitrogen-based Brayton cycle for power conversion. That reactor is called R1. Mark-1, according to the company, is the bridge between the demonstration work of Mark-0 and the deployment of R1.

Antares is planning to operate Mark-1 at full electrical power for six months in 2027 at INL. Beyond that, the company plans to deploy multiple R1 units at Fort Bragg, under the Army's Janus Program, with the first unit planned for a 2028 deployment.

Stepping back from the company-specific details, this milestone also represents the first time a company has earned an NSDA for a second reactor design through this new DOE authorization framework.

While not explicitly confirmed by Antares, it is likely that the Mark-1 is progressing through the Nuclear Energy Launch Pad. Launch Pad was created to extend and expand on the pathway established by the Reactor Pilot Program. Antares was selected for the program in August.

Last Energy milestone: On October 7, Last Energy announced the DOE's approval of its DSA for its pilot reactor. The company is ultimately pursuing a 20-MWe, LEU-fueled pressurized water reactor.

The company previously has called this pilot project the PWR-5 and described it as using "the same physical reactor geometry" of the PWR-20 with "reduced fuel enrichment scaled for 5 MW of electrical output." This pilot reactor would demonstrate low-power criticality "before progressing to electricity generation."

Notably, the name "PWR-5" does not appear in Last Energy's newest announcement, but the company still said it is planning to use its pilot to "validate commercial-ready performance and advance into power generation."

Last Energy's pilot facility is located at Texas A&M University's RELLIS campus. It is one of two companies whose Reactor Pilot Program project is centered on the campus-the other is Terrestrial Energy.

Radiant milestone: On October 29, Radiant announced the DOE's approval of its DSA for its Kaleidos demonstration unit (KDU). The company is planning to test this pilot at full-power for 60 effective full-power days at INL's Demonstration of Microreactor Experiments (DOME). This scheduled testing "will be the industry's only full-power, extended-duration demonstration of a nuclear microreactor to date," according to the company.

Radiant added that KDU "uses a similar reactor design and custom-designed fuel as the units Radiant plans to deliver to customers." That design is a 1-MWe, helium-cooled, TRISO-fueled reactor.

After testing at DOME, Radiant has near-term plans to deploy at Buckley Space Force Base, the Army's Fort Benning, and Naval Weapons Station Crane.