- Antares Nuclear has completed a criticality test of its Mark-0 microreactor
- The company became the first Reactor Pilot Program participant to complete a fueled reactor test
- The achievement moves advanced microreactor technology closer to real-world deployment
Antares Nuclear successfully conducted a zero-power criticality test of its Mark-0 demonstrator reactor at Idaho National Laboratory on June 4, bringing the company closer to deploying microreactor technology for defense and energy uses.
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Why Is the Criticality Test Significant?
The U.S. Army said Friday, following the test, Antares became the first company participating in the Department of Energy’s Reactor Pilot Program to secure authorization and complete a fueled criticality test. The program, established under Executive Order 14301, is intended to accelerate advanced reactor development and targets having at least three reactors reach criticality by July 4.
Energy Secretary Chris Wright described the achievement as an important step in advancing microreactor technology.
“These technologies will play a critical role in strengthening U.S. energy security for both military and civilian applications,” Wright added.
How Did the Army Support the Effort?
The Army worked with DOE to help ensure fuel was available in time for the testing schedule and provided expertise during the safety review process. The effort supports the Army’s Janus Program, which seeks to deploy advanced nuclear microreactors to strengthen energy resilience at military installations.
Jeff Waksman, principal deputy assistant secretary of the Army for installations, energy and environment, said the Mark-0 reactor test advances the Army’s goal of fielding reliable nuclear power capabilities for operational use.
“A microreactor is now generating neutrons,” said Waksman. “Next, we need a microreactor to generate electrons, and we need to do so with sufficient reliability and maintainability to improve energy resilience at military installations.”
The achievement comes as the Army advances its Janus Program. In a recent interview with ExecutiveGov, Waksman said the service expects to announce Janus contract awards this summer and that the Defense Innovation Unit has budgeted hundreds of millions of dollars to support the initiative in fiscal year 2027.
