goingcritical:last-energy-pwr-5United States · Microreactor
Last Energy PWR-5
Status: Under construction target criticality Q3 2026 (confidence: medium) Reactor status full glossary → Announced Publicly announced — a site and design are proposed, but construction has not begun. Site preparation Early site and civil works are under way; the first safety-related ("nuclear") concrete has not yet been poured. Under construction Formal construction has begun, marked by the first nuclear concrete. Fuel loaded Nuclear fuel has been loaded into the core. The reactor is fuelled but has not yet gone critical. Critical Has reached first criticality — a self-sustaining chain reaction, usually at low power — but is not yet connected to the grid. Grid connected Synchronised to the electrical grid and exporting power for the first time, but still in commissioning and power-ascension testing — not yet in commercial service. In commercial operation — the operator has formally declared the unit in regular commercial service. Shut down Permanently shut down and no longer generating; may be defuelled, undergoing decommissioning, or preserved in place. Canceled Abandoned before completion.
Site: Texas A&M University RELLIS Campus, Bryan, Texas
Pilot-scale PWR at Texas A&M RELLIS (land lease Oct 2025; PDSA approved late May 2026)
Company targets initial criticality test in summer 2026, pending DOE authorization; construction reported complete with critical components installed as of early July 2026
Details
| Design | PWR-5 — 5-MWe scaled pressurized water reactor prototype of the commercial 20-MWe PWR-20 |
| Capacity | 5 MW (thermal where reported) |
Milestone history
- Announced August 12, 2025
- Construction start —
- Fuel load —
- First criticality target Q3 2026