Six months have passed since we last provided a public update on our technical roadmap. With the approval of the Nuclear Safety Design Agreement (NSDA) for Mark-1 and our PDSA in review, I’ve decided it’s time to provide an update on our plans and objectives.
On June 4, 2026, Mark-0 became the first new reactor design to reach criticality in over 40 years. Since then, our roadmap has remained remarkably consistent. We always sought to make neutrons in 2026, electrons (in a reactor) in 2027, and achieve commercial deployments in 2028.
Antares’ Mark-0 reactor inside Idaho National Laboratory’s Reactors and Critical Experiments facility on June 3, 2026. Mark-0 achieved criticality the following day.
Our overarching goal is to deploy the first of multiple reactors at Fort Bragg and Joint Base San Antonio. Fort Bragg, the most important Army installation and one of the most important bases in the world, comes first in 2028, and we believe our intermediate milestones will enable us to be the first commercially deployed microreactor in the United States. We are equally committed to delivering for the Air Force at Joint Base San Antonio, a mission-critical installation and a customer we are proud to partner with under its Advanced Nuclear Power Initiative. Here is how we will achieve that.
To unlock deployment speed, the most important thing is comprehensive, sufficient testing of all of the major subsystems and their integrated effects. That is what Mark-1 is meant to achieve. Mark-1 is designed to operate at full power and electricity production consistent with what we will deploy commercially at Fort Bragg. Furthermore, it will not simply be a quick demonstration for 6 days or less; it will instead run for several months, with a goal of 6 months of continuous power. We believe this is how you partner with the customer to de-risk their deployment, provide technical demonstrations that truly retire technical uncertainties, and minimize the changes needed for subsequent deployments.
Given that Mark-0 established the Idaho National Laboratory’s (INL) Reactors and Critical Experiments (RACE) facility as a reactor facility, and we fabricated all of the TRISO fuel for the Mark-1 test, we have a relatively defined path forward towards operations in 2027. Therefore, we believe that Mark-1 is likely to be the first microreactor demonstration in America at commercially relevant thermal power, including a commercially relevant electricity generation system (a recuperated closed-cycle nitrogen Brayton system).
Mark-0 established most of the reactor procedures, safety basis, control systems, and supply chain. In the lead up to Mark-1, we are testing the first serial number of our power conversion system (PCS) in our HQ, Antares Prime, inside of 2026. This power conversion test will utilize surrogate heat pipes in our primary heat exchanger (PHX). Nitrogen will circulate through each individual tube and fin heat pipe heat exchanger before being transported to the PCS skid. In parallel, we are testing heat pipes multiple times a week. We believe we are now routinely making and operating the highest-thermal-throughput alkali metal heat pipes in North America.
A heat pipe glows during testing at Antares Prime, the company’s factory in Torrance, California.
As we continue to derisk our primary coolant (heat pipes) and power conversion system, we see a path to closure on the Mark-1 2027 timeline. We are not completely out of the woods, and will likely continue to run electrically heated integrated effects tests to further build confidence in the thermomechanical interfaces. But as we wrap up the final design, we are starting to exit the game of whack-a-mole that is reactor design and hone in on a safety basis that fully closes for our test and future customer deployments. As Mark-1 risk is bought down by non-nuclear single and integrated effects testing, Mark-1 will be the demonstration that further gives us confidence to deploy under the Army Janus program in 2028.
Antares installs the primary heat exchanger on the power conversion system test stand at Antares Prime in Torrance, California, where the company conducts non-nuclear testing of reactor subsystems.
In the months ahead, we will share more about our work and performance on the Janus program and what it means for iteration towards nth-of-a-kind performance and, eventually, scaled deployment. If you want to build fission power systems and see them deployed in the years ahead, Antares leads in hardware testing and deployment strategy. We will provide resilient energy to unlock mission capability for our customers. Come join Antares!
Jordan Bramble