DOE Pilot Program Demonstration Reactor by Antares Nuclear: status and timeline

DOE Pilot Program Demonstration Reactor

Antares's demonstration reactor achieved zero-power criticality in June 2026 as part of the DOE pilot program. It uses HALEU TRISO fuel and is progressing through power ascension.

PilotStage 3 of 5

Reached zero-power criticality June 2026. In power ascension testing with government partners.

Updated Jun 2026Checked 11 Oct0 updates this week

Milestones

Next · Power ascension testing

DOE pilot program selection2024Complete.
Zero-power criticality achieved at Idaho National LaboratoryJun 2026Complete.
Power ascension testingTarget Q3 2026Current milestone.
Full-power demonstrationTarget 2027Not yet reached.

Most important updates

Antares Nuclear reaches zero-power criticality in DOE Reactor Pilot Program, one of four companies to succeedJun 2026

Upcoming

Q3 2026Power ascension testing (next)
Q4 2026Power ascension and full-power operation
2027Full-power demonstration
2027Fort Bragg deployment under Janus Program
2027Air Force space reactor demonstration (R1-S)

Current obstacles

HALEU enrichment infrastructureU.S. domestic HALEU production capacity is limited and still ramping up. International fuel supply chains remain constrained.
Licensing for novel designsThe NRC is still developing regulatory frameworks for some advanced reactor concepts. Licensing timelines and precedent are uncertain.

Physics limits

Enrichment limits on civil power reactorsInternational agreements (NPT) restrict civilian nuclear fuel enrichment. HALEU sits at the upper boundary, requiring careful security and non-proliferation frameworks.
Microreactor economicsSmaller reactors have higher per-megawatt costs. Deployment in remote or niche markets can justify the cost, but mass-market scaling faces economic headwinds.

How it works

2 parts

Fuel

HALEU TRISO particles

HALEU-enriched TRISO fuel particles are suspended in graphite. HALEU (5–20% enrichment) is higher than commercial fuel.

Operation

Criticality and power control

The reactor operates at thermal power through neutron multiplication. Heat is extracted for electricity or process applications.

Spec sheet

Spec	DOE Pilot Program Demonstration Reactor
Fuel type	HALEU TRISO (high-assay low-enriched uranium)^R (reported)
Reactor class	Advanced microreactor^R (reported)

^R reported by the company

Update log

1 update

Jun 2026

Major: Antares Nuclear reaches zero-power criticality in DOE Reactor Pilot Program, one of four companies to succeedPressTest

About Antares Nuclear

The team behind DOE Pilot Program Demonstration Reactor

Antares Nuclear

Microreactor, advanced reactor design, HALEU fuel, DOE demonstration

Antares Nuclear is developing advanced microreactor technology selected for the U.S. Department of Energy's Reactor Pilot Program. The company achieved zero-power criticality with its demonstration reactor in June 2026 using HALEU (high-assay low-enriched uranium) TRISO fuel.

Antares reached zero-power criticality in June 2026, one of four companies in the DOE pilot program.
The reactor design uses HALEU TRISO fuel and supports military and space propulsion applications.
The company won a U.S. Army Janus Program contract and a $161M Air Force Space Force contract for space reactor development.

Company profile →

Headquarters: United States
Status: Private
Valuation: private
Works in: EnergyFission
Coverage: 1 program · 3 updateslatest 1 Sep 2026checked 10 Oct
Customers: U.S. Department of Defense
Partners: U.S. Department of EnergyNASA

Spec

DOE Pilot Program Demonstration Reactor

Fuel type

HALEU TRISO (high-assay low-enriched uranium)^R (reported)

Reactor class

Advanced microreactor^R (reported)