goingcritical:hamaoka-4Japan · Power reactor
Hamaoka 4
Status: Operating critical since December 2, 1992 Reactor status full glossary → Announced Publicly announced — a site and design are proposed, but construction has not begun. Site preparation Early site and civil works are under way; the first safety-related ("nuclear") concrete has not yet been poured. Under construction Formal construction has begun, marked by the first nuclear concrete. Fuel loaded Nuclear fuel has been loaded into the core. The reactor is fuelled but has not yet gone critical. Critical Has reached first criticality — a self-sustaining chain reaction, usually at low power — but is not yet connected to the grid. Grid connected Synchronised to the electrical grid and exporting power for the first time, but still in commissioning and power-ascension testing — not yet in commercial service. In commercial operation — the operator has formally declared the unit in regular commercial service. Shut down Permanently shut down and no longer generating; may be defuelled, undergoing decommissioning, or preserved in place. Canceled Abandoned before completion.
Site: Omaezaki, Shizuoka
Idle since the government-requested Hamaoka shutdown of 2011; Chubu withdrew its NRA restart screening application on 25 September 2026 (board decision 14 September) after an outside inquiry found design-basis seismic data had been understated since around 2012 — screening resets to the pre-application stage and Chubu says it intends to re-apply after internal reform, with no timetable. Not permanently closed and not being decommissioned.
Details
| Design | BWR-5 |
| Electrical output | 1,092 MWe |
Milestone history
- Announced —
- Construction start October 13, 1989
- Fuel load —
- First criticality December 2, 1992
- Grid connection January 27, 1993
- Commercial operation September 3, 1993