US nuclear battery achieves first critical reaction, plans full-power test in 2027

A US-developed nuclear battery has achieved its first controlled chain reaction in about 150 days, with a full-power demonstration planned for 2027 at Idaho National Laboratory. US transportable nuclear reactor developer Deployable Energy announced on Oct. 7 that the Department of Energy (DOE) has selected its Unity nuclear battery for testing at the laboratory's Demonstration of Microreactor Experiments (DOME) facility. The upcoming test will verify whether the compact reactor can operate at full power, be transported with fuel loaded, and be relocated after operation. The company is developing Unity to provide continuous power for industrial sites, vessels and remote areas. The selection follows a June 30 milestone when Unity reached criticality — the stage at which a reactor sustains a controlled nuclear chain reaction. According to the company, this progress was achieved about 150 days after the project began, making it the first developer to reach this stage under the National Reactor Innovation Center's (NRIC) Nuclear Energy Starter Platform initiative.

Purpose and significance of test plan

Reaching criticality confirms the reactor can sustain a chain reaction, but it does not mean the system can deliver its intended power output under operating conditions. The 2027 test plan aims to verify the next phase. Deployable Energy plans to fuel Unity at the factory, then transport the fueled reactor to INL, install it in DOME and operate it at full power. After testing, the company intends to move the reactor to another location within the laboratory and complete the nuclear fuel management process. These steps will test not only the reactor itself but also provide data on transport, installation, operation and redeployment — crucial for systems designed to avoid building traditional nuclear plants at every site. DOME is housed within the containment structure of INL's former Experimental Breeder Reactor II, and the facility can accommodate experimental reactors producing up to 20 megawatts thermal. That figure describes the test facility's capacity, not Unity's expected output. "Build the reactor, learn fast, and pivot to manufacturing: that's the model the advanced nuclear industry needs," said Bobby Gallagher, co-founder and CEO of Deployable Energy.

Potential applications for modular system

Unlike large nuclear plants built at fixed sites, Unity is being developed as a modular system that can be manufactured and transported to locations needing reliable power. Potential applications include industrial facilities, maritime operations and remote areas where conventional power infrastructure may be unavailable or impractical. The demonstration will also test whether a fueled reactor can be moved and installed through a repeatable process, rather than requiring large-scale construction at each deployment site. Deployable Energy said the Nuclear Regulatory Commission (NRC), which regulates nuclear energy, has observed its early criticality testing and will continue observing these demonstrations. The planned tests will support future licensing discussions but do not themselves constitute commercial regulatory approval. The company will work with NRIC and INL over the coming months on engineering, fuel preparation, safety reviews and test planning. Deployable Energy also said it has been selected to participate in a separate DOE-authorized commercial nuclear maritime demonstration project. That project is independent of the 2027 DOME test plan. The full-power test remains a future milestone, and its results will help determine whether Unity's reactor design and proposed deployment process can support repeatable manufacturing and commercial use.

Item	Specification
Full-power test timing	2027
Thermal power output	Up to 20 megawatts
Time to achieve criticality	About 150 days

Unity nuclear battery's innovation and challenges

The development of the Unity nuclear battery marks a significant advance in nuclear energy technology, particularly in modularity and mobility. This design enables manufacturing and transport to locations where power is needed, reducing the need for traditional nuclear plant construction. Future tests will not only evaluate reactor performance but also provide data on transport and installation, which is critical for advancing nuclear energy commercialization. With continued regulatory attention, whether the project successfully achieves commercialization will influence the future development of the nuclear industry.