Trawsfynydd, the UK's only inland Magnox station (392 MWe), closed in 1991 and is the NDA's 'lead and learn' site for accelerated Magnox reactor decommissioning. All intermediate-level waste was retrieved by March 2026, and in October 2026 contractor Costain took over the reactor buildings to cut them from 54 m to about 25 m.
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Current state
| Status | Active dismantling |
| Country | United Kingdom |
| Location | Gwynedd (Snowdonia National Park), Wales |
| Site | Trawsfynydd |
| Units | Reactor 1, Reactor 2 |
| Unit count | 2 |
| Reactor types | Magnox |
| Net capacity (MWe) | 392 |
| Owner / licensee | Nuclear Decommissioning Authority (site licensee: Nuclear Restoration Services) |
| Decommissioning contractor | Costain (reactor height reduction) |
| Strategy | Mixed |
| Final shutdown | 1991 |
| Decommissioning start | 1995 |
| Spent fuel | Defueling completed by 1997. |
| Notable issue | Four-year reactor building height-reduction programme in a national park. |
Notes
Strategy mixed: early safestore-style approach being replaced by continuous/accelerated reactor dismantling.
Timeline
- 1965 — Trawsfynydd began operation. (source)
- 1991 — The station was retired. (source)
- 1997 — Defueling was completed. (source)
- 2020-07 — The NDA named Trawsfynydd the 'lead and learn' site for accelerated Magnox decommissioning. (source)
- 2026-03 — The final of almost 2,300 intermediate-level waste packages was placed in interim storage. (source)
- 2026-10-08 — NRS handed the reactor buildings area to Costain to begin height reduction. (source)
The timeline is append-only: corrections are added as new entries. Stated targets appear in the current-state table, never as milestones.
Related sites
- Berkeley (Magnox) SAFSTOR · United Kingdom
- Bradwell (Magnox) SAFSTOR · United Kingdom
- Brennilis (Monts d'Arrée EL-4) Active dismantling · France
- Dounreay (DFR and PFR fast reactors) Active dismantling · United Kingdom
- Dungeness B Fuel removal · United Kingdom
- Fermi Unit 1 (Enrico Fermi Atomic Power Plant) SAFSTOR · United States
- GE Vallecitos (VBWR and EVESR) Active dismantling · United States
- Hinkley Point B Active dismantling · United Kingdom
See all 72 sites in the Nuclear Decommissioning Tracker →
Sources
- Costain to reduce height of Trawsfynydd reactor buildings — World Nuclear News, checked 2026-10-11
- Trawsfynydd site — NRS Site Stakeholder Groups (primary), checked 2026-10-11
- Trawsfynydd takes next step towards Reactor Height Reduction — Nuclear Industry Association, checked 2026-10-11
- ONR introduces new regulatory approach for former Magnox nuclear sites — Office for Nuclear Regulation (primary), checked 2026-10-11