Sellafield is Britain's largest and most hazardous nuclear clean-up, covering the Calder Hall Magnox reactors (the world's first industrial-scale grid-connected nuclear station, 1956-2003) alongside legacy reprocessing plants, ponds and silos. The NDA expects clean-up to run until 2125 at an undiscounted cost of £136bn; Calder Hall was defueled in 2019 and its reactors are in care and maintenance.
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Current state
| Status | Active dismantling |
| Country | United Kingdom |
| Location | Seascale, Cumbria, England |
| Site | Sellafield |
| Units | Calder Hall 1, Calder Hall 2, Calder Hall 3, Calder Hall 4 |
| Unit count | 4 |
| Reactor types | Magnox |
| Net capacity (MWe) | 200 |
| Owner / licensee | Nuclear Decommissioning Authority (site licensee: Sellafield Ltd) |
| Decommissioning contractor | Sellafield Ltd |
| Strategy | Mixed |
| Final shutdown | 2003-03-31 |
| Decommissioning start | 2003 |
| Target completion | 2125 |
| Cost estimate | GBP 136bn (as of 2025-06-04) |
| Spent fuel | Calder Hall defueled by September 2019 (38,953 fuel rods sent for Magnox reprocessing); site stores much of the UK's spent fuel and plutonium. |
| Notable issue | Public Accounts Committee criticises repeated cost overruns and delays on major Sellafield projects; cost estimate up 18.8% since 2019. |
Notes
Scope is the whole Sellafield site clean-up (reactors are a small part). Cost is undiscounted and covers all Sellafield decommissioning, not just Calder Hall. Calder Hall 4 x 50 MWe net per WNN. PAC report published 4 June 2025.
Timeline
- 1956-10-17 — Calder Hall was opened as the world's first industrial-scale nuclear power station connected to a national grid. (source)
- 2003-03-31 — Calder Hall closed after 47 years of operation. (source)
- 2007-09 — Calder Hall's four cooling towers were demolished. (source)
- 2011 — Defueling of Calder Hall's reactors began. (source)
- 2019-09-03 — Sellafield Ltd completed defueling of Calder Hall; the reactor buildings entered care and maintenance. (source)
- 2025-06-04 — Parliament's Public Accounts Committee reported the Sellafield clean-up would cost £136bn and last until 2125. (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
- Decommissioning Sellafield (Public Accounts Committee report) — UK House of Commons Public Accounts Committee (primary), checked 2026-10-11
- Decommissioning the world's first commercial nuclear power station — Nuclear Decommissioning Authority (primary), checked 2026-10-11
- Sellafield completes defueling of Calder Hall — World Nuclear News, checked 2026-10-11
- Nuclear Power in the United Kingdom — World Nuclear Association, checked 2026-10-11