Mihama 3 is a 780 MWe (net) Kansai Electric PWR that in June 2021 became the first Japanese reactor restarted to operate beyond 40 years, after a decade offline. It is operable; it entered a periodic inspection in June 2026 after a turbine steam-leak shutdown in May.
Background: Palisades fuel loading: Holtec restart timeline and what comes next · NRC reactor licensing process, explained
Current state
| Status | Restarted |
| Country | Japan |
| Location | Mihama, Fukui Prefecture |
| Plant | Mihama |
| Unit | 3 |
| Operator | Kansai Electric Power |
| Reactor type | PWR |
| Net capacity (MWe) | 780 |
| Restart type | Post-Fukushima restart |
| Shut down | 2011-05-14 |
| Restarted | 2021-06-23 |
| Years offline | 10.1 |
| Regulator | NRA conformity approval 2016-10-05; beyond-40-year operation approved 2016-11-16 |
Notes
Kansai halted the unit in October 2021 because its specialised anti-terrorism facility was not complete (JAIF); it was available again from July 2022. Local consent date not verified.
Timeline
- 2011-05-14 — Mihama 3 entered a periodic inspection outage. (source)
- 2016-10-05 — The NRA officially approved the unit. (source)
- 2016-11-16 — The NRA approved operation beyond 40 years. (source)
- 2021-06-23 — Kansai restarted Mihama 3, the first Japanese restart of a reactor over 40 years old. (source)
- 2021-07-27 — The unit resumed commercial operation. (source)
- 2026-05-08 — Mihama 3 was manually shut down to inspect a steam leak from the high-pressure turbine. (source)
- 2026-06-16 — The unit was shut down for a periodic inspection. (source)
The timeline is append-only: corrections are added as new entries. Stated targets appear in the current-state table, never as milestones.
Related units
- Genkai Unit 3 Restarted · Japan
- Genkai Unit 4 Restarted · Japan
- Hamaoka Unit 3 Cancelled · Japan
- Hamaoka Unit 4 Cancelled · Japan
- Higashidori Unit 1 (Tohoku Electric) Under review · Japan
- Ikata Unit 3 Restarted · Japan
- Kashiwazaki-Kariwa Unit 6 Restarted · Japan
- Kashiwazaki-Kariwa Unit 7 Approved · Japan
See all 45 units in the Nuclear Plant Restarts Tracker →
Sources
- Current Status of Nuclear Power Plants in Japan as of August 7, 2026 — Japan Atomic Industrial Forum (JAIF) (primary), checked 2026-10-11
- Current Status of Nuclear Power Plants in Japan as of March 14, 2019 — Japan Atomic Industrial Forum (JAIF) (primary), checked 2026-10-11
- Nuclear Power in Japan — World Nuclear Association, checked 2026-10-11
- Mihama-3 Restarted After Decade-long Hiatus: First Restart in Japan of a Reactor Operating Beyond 40 Years — JAIF, checked 2026-10-11