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. Operating 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.

Developer: Westinghouse

Site: DOME test bed (NRIC), Idaho National Laboratory, Idaho

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DOME test bed (NRIC), Idaho National Laboratory, Idaho43.5850° N, 112.8500° W
Summary:

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. Westinghouse completed zero-power criticality testing for the eVinci design on 2026-08-24 at LANL's NCERC, Nevada National Security Site — a design-validation critical experiment, not this reactor; no source names the hardware or NCERC assembly used, and no source describes it as a first criticality.

Details

DesignHeat-pipe-cooled, graphite-moderated, HALEU TRISO-fueled microreactor — a 3 MWt scaled (roughly one-fifth) version of the 5 MWe / 15 MWt commercial eVinci
CapacityUndisclosed

Milestone history

  1. Announced —
  2. Construction start —
  3. Fuel load —
  4. First criticality —

References

  1. Westinghouse, eVinci microreactor achieves zero-power criticality (25 August 2026)
  2. POWER Magazine (26 Aug 2026) — distinguishes the NCERC physics-validation experiment from the 3 MWth DOME test reactor
  3. WNN, approval of Westinghouse test microreactor progresses
  4. NRIC, DOME demonstrators