Last Energy secures approval for Texas pilot microreactor documented safety analysis

U.S. commercial developer Last Energy has received approval for the documented safety analysis (DSA) for its pilot facility at Texas A&M University's RELLIS campus. The DSA is the final step in the U.S. Department of Energy (DOE) review process, after which a startup authorization for reactor criticality and operation will be issued. Demand for carbon-free energy is driving a nuclear resurgence, promising emissions-free, on-demand power. Historically, nuclear energy has required massive facilities and has often been associated with delays and cost overruns, but the future of nuclear seeks to build smaller reactors to control costs.

Small modular reactors (SMRs) and microreactors are designed with the future of nuclear energy in mind. SMRs can generate up to 300 megawatts (MW) of electricity, while microreactors are even smaller structures with outputs not exceeding 20 MW.

Microreactor Design and Technology

Last Energy, the commercial arm of the Washington, D.C.-based clean energy research organization Energy Impact Center, is building a pilot facility at Texas A&M RELLIS that will use the same nuclear core as its commercial-scale reactors. Last Energy's microreactor employs proven pressurized water reactor (PWR) technology and uses a proprietary steel containment design that seals it inside a 1,000-ton vault. This approach helps the company fit the reactor compactly within a nuclear island of no more than 114 square feet, roughly the size of a single-car parking space.

Multiple such nuclear islands can be connected in series or in parallel to Last Energy's factory-built modular steam plants to scale output or extend facility uptime.

These reactors use low-enriched uranium (LEU) fuel with less than 5% uranium content, ensuring supply for commercial use. The company plans to offer full-service reactor solutions, including design, ownership, and operation as an independent power producer, and will supply power to data centers and off-grid, energy-intensive industrial sites via power purchase agreements.

Pilot Facility Progress and Plans

In October 2025, Last Energy reached an agreement with Texas A&M University to build a 5 MW microreactor, called the PWR-5, at the university's RELLIS facility; the pilot will use the same full-scale reactor core as the commercial reactors. The company was selected in August of the same year for the DOE's reactor pilot program to accelerate reactor demonstration. In May 2026, the Texas pilot facility completed its preliminary documented safety analysis (PDSA). With the recent DSA approval, Last Energy has completed the most comprehensive safety analysis for the reactor and the Texas facility, paving the way for the review.

This is the final step in the DOE review process, after which a startup authorization for reactor criticality and operation will be issued. All of these steps apply only to the demonstration reactor. Last Energy must follow procedures established by the Nuclear Regulatory Commission (NRC) to obtain the approvals needed for future commercial deployments.

Impact of Microreactors on the Future of Nuclear Energy

As demand for carbon-free energy grows, the development of microreactors signals a nuclear resurgence. Last Energy's microreactor design is not only compact but also effectively controls costs, which is critical for the future commercial operation of nuclear energy. By using proven technology and low-enriched uranium fuel, Last Energy aims to provide safe and sustainable power supply. Moreover, the documented safety analysis approval marks significant progress for the company's further development in the nuclear sector, paving the way for future commercial deployments.