Nuclear startup Last Energy raises $100M for its steel-encased micro reactor

Last Energy, a nuclear startup focused on small modular reactors (SMRs), has raised $100 million in a Series C funding round led by the Astera Institute, with participation from multiple investors. The company aims to produce compact nuclear power plants capable of generating 20 megawatts of electricity—enough to power about 15,000 homes. This funding will support the construction of a 5-megawatt pilot reactor at a Texas A&M-leased site, with plans to activate it next year and begin commercial production of the larger 20-megawatt units by 2028. Last Energy’s approach revives a decades-old pressurized water reactor design originally developed for the world’s first nuclear-powered merchant ship, scaling it up to commercial use. A distinctive feature of Last Energy’s reactors is their steel-encased cores, which are permanently sealed within 1,000 tons of steel—estimated to cost around $1 million—rather than using nuclear-grade concrete. The reactors