Last Energy wins DOE safety approval for Texas A&M pilot reactor

Last Energy has crossed a key licensing gate for its Texas A&M-RELLIS pilot, but the hard part is still ahead: turning a safety file into a reactor that can be built, fueled and brought to criticality.

The U.S. Department of Energy approved the Preliminary Documented Safety Analysis for Last Energy’s PWR-5 on May 29, 2026, giving the 5-megawatt pilot reactor a formal safety basis under the DOE authorization pathway. For this project, the PDSA is not the finish line. It is the document that lays out the preliminary safety case for the reactor, the facility and planned operations, which means the project has moved deeper into the agency’s process but has not yet reached fuel loading or routine operation.

That distinction matters for anyone tracking whether first-of-a-kind small reactors are leaving the slide deck and entering the yard. Last Energy’s vice-president of development, Adam Lenarz, said the approval was a major step in moving the PWR-5 from construction into operations. The company said it has been advancing construction, equipment procurement, fuel fabrication and safety documentation in parallel, a strategy that can compress schedules if all of the workstreams stay aligned.

The PWR-5 is being developed under the DOE Reactor Pilot Program, which the agency launched on August 12, 2025, with 11 advanced reactor projects selected for the fast-track effort. DOE said its goal was to construct, operate and achieve criticality of at least three test reactors by July 4, 2026, using the DOE authorization process rather than the traditional commercial licensing route through the Nuclear Regulatory Commission.

At Texas A&M-RELLIS in Bryan-College Station, the project has already moved beyond paperwork. Texas A&M System materials say the land lease has been signed, construction began in 2026, key reactor components have been delivered to the site and the reactor building has advanced. The system also says the pilot is fully financed with private capital and that testing is expected to begin in the summer of 2026.

Last Energy says the PWR-5 uses the same physical reactor geometry as its planned 20-megawatt PWR-20 commercial design, but scaled down and paired with reduced fuel enrichment. The company’s first target is safe, low-power criticality, with electricity generation to follow. That makes this more than a laboratory exercise: it is intended as a bridge from a pilot site at Texas A&M-RELLIS to a larger microreactor deployment model built around factory fabrication, transportable equipment and existing supply chains.

The milestone is real, and so is the remaining checklist. The approval means the safety case is now on the record; the reactor still has to finish the race from paper to steel, from fabricated fuel to fuel on site, and from construction activity to the first criticality pulse.