Current state
| Status | Commissioning |
| Design | VVER-440/V-213 (PWR) |
| Net capacity | 440 MWe |
| Country | Slovakia |
| Vendor | Škoda/Rosatom lineage |
| Owner / operator | Slovenské elektrárne |
| Construction start | 1987 |
| Original COD target | — |
| Current COD estimate | 2026 |
| Schedule slippage | — |
Notes
Soviet-era start; completion resumed decades later - unit 3 entered service 2023. First criticality (2026-08-05/06) now confirmed by operator press release, ANS Nuclear Newswire and trade press. Power generation from 2026-09-21; grid synchronisation at 20% and 144-hour demonstration run still ahead, so commercial operation likely late 2026 to Q1 2027.
Milestone log
- 2026-06-16 — Listed as under construction in the WNA world table, grid connection estimated 2026 (source)
- 2026-06-29 — First fuel assembly loaded into the reactor at 15:45 local time, beginning fuel load (operator announcement via WNN, 2026-06-30) (source)
- 2026-07-20 — Reactor assembly and sealing completed; unit entered physical start-up tests preceding first criticality (Slovenske elektrarne via WNN) (source)
- 2026-08-05 — First criticality reported (NucNet, published 2026-08-07 with 2026-08-05 dateline); single trade-press source so far - awaiting Slovenske elektrarne / IAEA PRIS confirmation (source)
- 2026-08-06 — First criticality confirmed by operator Slovenske Elektrarne (press release 2026-08-07): reactor critical at 22:10, minimum controlled power at 22:31; power ascension tests to follow (source)
- 2026-09-21 — Power generation begins at 15:33 (operator via WNN); staged commissioning at 5/20/35/55/75/90% with grid synchronisation at 20%, then 144-hour full-power run before commercial operation (source)
The milestone log is append-only: corrections are recorded as new entries, never rewrites. Full history via /api/v1/changes.
NNN coverage
About Mochovce-4
On the VVER-440 design
Sources
- https://world-nuclear.org/information-library/current-and-future-generation/plans-for-new-reactors-worldwide
- https://www.world-nuclear-news.org/articles/fuel-loading-begins-at-slovakias-mochovce-4
- https://www.world-nuclear-news.org/articles/mochovce-4-reactor-assembly-completed
- https://www.nucnet.org/news/slovakia-s-mochovce-4-nuclear-power-plant-reaches-first-criticality-8-5-2026
- https://www.seas.sk/pre-media/tlacove-spravy/slovenske-elektrarne-ozivili-reaktor-4-bloku-jadrovej-elektrarne-mochovce/
- https://www.ans.org/news/article-8287/slovakias-newest-reactor-achieves-criticality/
- https://pris.iaea.org/pris/
- https://pris.iaea.org/PRIS/CountryStatistics/CountryDetails.aspx?current=SK
- https://www.world-nuclear-news.org/articles/power-start-up-for-mochovce-4