BWRX-300
GE-Hitachi's boiling water SMR, derived from the ABWR, under construction at Darlington since 2025.
Natural-circulation boiling-water SMR. ARIS 2024 states 870 MWt and approximately 300 MWe net in its electricity-only configuration; the Canadian licence applies to one specific Darlington unit, not to a universal design certification.
- Stated output
- 870 MWt · 300 MWe net · per unit
- Maturity
- Detailed design
- Developer
- GE Vernova Hitachi Nuclear Energy
- Origin
- United States / Japan
Energy and applications
Published magnitudes; this is not an engineering diagram.
Three different states
Maturity, licensing and deployment are not equivalent.
Maturity
Detailed designHow far the published engineering has progressed.
Licensing and review
3 regulatory readingsWhat a regulator decided, where and on what date.
Linked deployment
1 geolocated unitWhich projects or units are linked to the design.
Linked deployment
| Plant | Unit | Country | Dataset status |
|---|---|---|---|
| Darlington New | 1 | Canada | construction |
Licensing and review
What a regulator decided, where and on what date.
| Jurisdiction | Reading | Method | Date |
|---|---|---|---|
| Canada · Darlington | Site construction authorized | Power reactor construction licence for one BWRX-300, valid through 31 March 2035 | 2025-04-04 |
| Canada | Pre-licensing review | Combined Phase 1 and 2 vendor design review completed; the CNSC states that this review is not a licence | 2023-03-15 |
| United States | Pre-licensing review | NRC pre-application review of topical reports and design white papers | 2026-09-09 |
Technical sources
- IAEA ARIS · SMR Catalogue 2024IAEA · 2024
- CNSC · BWRX-300 combined Phase 1 and 2 vendor design reviewRegulator · 2023-03-15
- CNSC · Darlington New Nuclear ProjectRegulator · 2026-03-30
- U.S. NRC · GVH BWRX-300 pre-application activitiesRegulator · 2026-09-09
How it works and why it matters
The BWRX-300 is a 300 MWe natural-circulation BWR that simplifies the ABWR: no recirculation pumps, isolation valves integrated into the vessel and passive cooling by isolation condensers for seven days. It is the only boiling water SMR under construction.
Ontario Power Generation started building the first unit at Darlington in May 2025, with four planned by 2035. Tennessee Valley Authority, in the United States, and Poland follow.
Quick facts
| Power | ≈ 300 MWe |
|---|---|
| Type | natural-circulation BWR |
| Construction | Darlington, Canada, since May 2025 |
| First operation | 2029 to 2030 |