If you want to design a reactor, you have to build one.

That’s the philosophy behind our Electrically-Heated Demonstration Unit (EDU) — the first in a series of development units that let us validate our reactor design with hardware, not hypotheticals.

What is the EDU?

The EDU is an electrically-heated assembly that enables thermal and mechanical testing of full-scale components and sub-systems long before we fuel our first reactor.

In this first EDU we manufactured and sourced all of the major core and heat exchanger components that we will use in our reactors - graphite moderator blocks, sodium heat pipes, vessels, and transport cradle. We leveraged test facilities that allowed us to expose the EDU to real-world operating conditions and then rapidly analyze and evaluate the hardware, interfaces, and overall system performance. 

Why did we build the EDU?

We believe that the fastest path to turning on our first reactor is by building, testing, and validating our designs with real hardware in real operating environments. The nuclear industry has often been plagued by “paper reactors” that never leave the design phase, and we are determined to avoid that.

For this first EDU, our goal wasto test the interface between our graphite moderator blocks and our heat pipes at temperature, the effective throughput of our sodium heat pipes, and our ability to transfer heat from our heat pipes by flowing nitrogen through our heat exchanger. Along the way we learned invaluable lessons on how to assemble, transport, and instrument future reactors.

What did we learn from the first EDU?

Since April, our team has been running a series of tests that are already influencing our reactor design. In addition to validating the performance of individual components and interfaces, we iterated through numerous test cases that demonstrated how our reactor will perform in different situations. Most importantly, we recorded hundreds of hours of data that allowed us to validate our startup behavior, transient and steady-state environments, and shutdown.

We also faced many unexpected challenges along the way - learning how to assemble, instrument, and maneuver our hardware now strengthens our readiness for operating reactors in the field.

Each design–build–test cycle matures more than just our reactor architecture. It improves our team’s ability to design, build, and operate together — and it builds the operational muscle we need across supply chain, manufacturing, and integration as we prepare to site our first reactors.

What’s next?

This EDU is just the first step.

We’re building more electrically-heated prototypes to validate the full reactor system end-to-end. These lessons directly inform the design, safety case, and manufacturing approach for our first reactors.

This will culminate in our next major milestone: Taking an advanced reactor critical on American soil by July 4, 2026.

That criticality test will validate our core physics and unlock the path to our first power-producing reactor demonstration in 2027. This is how we ensure energy and resiliency for our nation’s most critical infrastructure, and how we unlock new capabilities on earth and in space.