goingcritical:evinci-ntrUnited States · Microreactor
eVinci Nuclear Test Reactor
Status: Announced 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: DOME test bed (NRIC), Idaho National Laboratory, Idaho
The first eVinci unit intended for fueled operation, to be sited in NRIC's DOME test bed at Idaho National Laboratory
No criticality date announced; DOE approval of the Preliminary Safety Design Report is one of four submissions required to site it at DOME, and DOME is occupied by Radiant's Kaleidos under exclusive access from August 2026. Two zero-power critical experiments for the eVinci design have now run at LANL's NCERC, Nevada National Security Site — the first on 2026-08-24, and a second high-temperature run on 2026-09-03 that reached criticality at 663 °C with a peak core temperature of 1,011 °C, a record for a reactivity measurement at NCERC. Both are design-validation critical experiments, not this reactor going critical; DOE and Westinghouse describe only "the eVinci test", no source names the hardware or NCERC assembly used, and no source describes either run as a first criticality.
Details
| Design | Heat-pipe-cooled, graphite-moderated, HALEU TRISO-fueled microreactor — a 3 MWt scaled (roughly one-fifth) version of the 5 MWe / 15 MWt commercial eVinci |
| Capacity | Undisclosed |
Milestone history
- Announced —
- Construction start —
- Fuel load —
- First criticality —
References
- Westinghouse, eVinci microreactor achieves zero-power criticality (25 August 2026)
- POWER Magazine (26 Aug 2026) — distinguishes the NCERC physics-validation experiment from the 3 MWth DOME test reactor
- WNN, approval of Westinghouse test microreactor progresses
- NRIC, DOME demonstrators
- DOE Office of Nuclear Energy (16 Sep 2026) — "On September 3, 2026, the eVinci test reached criticality at 663 degrees Celsius"; peak core 1,011 °C, a record for a reactivity measurement at NCERC
- Westinghouse (15 Sep 2026) — eVinci achieves zero-power high-temperature criticality
- WNN (15 Sep 2026) — eVinci sets temperature record during zero-power criticality tests