Microreactors Reach Criticality; Walmart Signs Nuclear Deal

Deployable Energy’s Unity microreactor reached criticality at Idaho National Laboratory, completing the third advanced reactor demonstration called for in a May 2025 presidential executive order. Constellation Energy also signed a long-term power purchase agreement to supply about 176 megawatts from the Dresden Clean Energy Center in Illinois to a Walmart distribution center in Belvidere.

The executive order set a target for three advanced reactors to reach criticality by July 4, 2026. Antares Nuclear and Valar Atomics achieved the first two criticalities in June. The demonstrations took place as part of the Department of Energy’s Reactor Pilot Program at Idaho National Laboratory.

Companies including BWX Technologies and Mirion Technologies are supplying fuel components and instrumentation for the microreactor projects. Suppliers of fabrication and measurement equipment reported increased orders tied to demonstration programs and test schedules. The Department of Energy has announced programs and funding, including a loan initiative, to accelerate domestic manufacturing for fuel, components and instrumentation.

Constellation’s power purchase agreement covers about 176 MW from Dresden and is intended to serve Walmart’s high-technology distribution center in Belvidere. The Dresden site houses two boiling water reactors. The contract includes provisions to support reactor uprates aimed at increasing output from existing units.

A reactor uprate is a set of equipment upgrades, testing and regulatory steps that raise a plant’s generation capacity without constructing a new reactor. Uprates typically require engineering work, testing and approval from regulators and can increase available output for local customers.

Market products that track the nuclear sector include companies positioned to supply both advanced reactor demonstrations and upgrades at operating plants. An index used by one exchange-traded fund includes firms such as BWX Technologies, GE Vernova, Flowserve and Mirion Technologies across fuel, equipment and services supply chains.

The recent events cover both testing of new microreactor designs and contracted power from existing commercial reactors. The DOE program, supplier activity and the Constellation-Walmart agreement are part of planned testing schedules and plant enhancement projects now under way.