Mochovce-4

Current state

Notes

Soviet-era start; completion resumed decades later - unit 3 entered service 2023. Fuel load began 2026-06-29; physical start-up tests from 2026-07-20; first criticality reported 2026-08-05 by NucNet but not yet confirmed by a second independent source (operator press page and PRIS not yet updated) - confidence medium until confirmed. Grid connection and 144-hour demonstration run still ahead; COD estimate 2026 unchanged.

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)

The milestone log is append-only: corrections are recorded as new entries, never rewrites. Full history via /api/v1/changes.

Sources

1. https://world-nuclear.org/information-library/current-and-future-generation/plans-for-new-reactors-worldwide
2. https://www.world-nuclear-news.org/articles/fuel-loading-begins-at-slovakias-mochovce-4
3. https://www.world-nuclear-news.org/articles/mochovce-4-reactor-assembly-completed
4. https://www.nucnet.org/news/slovakia-s-mochovce-4-nuclear-power-plant-reaches-first-criticality-8-5-2026
5. https://pris.iaea.org/pris/
6. https://pris.iaea.org/PRIS/CountryStatistics/CountryDetails.aspx?current=SK