Overview
- The No. 6 unit at the Kashiwazaki-Kariwa plant reached criticality on Jan. 21 before an overnight alarm during control‑rod withdrawal led TEPCO to stop the startup and move to a full shutdown for checks.
- TEPCO said the reactor remains stable, operators reinserted control rods, and no abnormal radiation levels were recorded; the site chief cautioned the probe will take longer than a day or two.
- The restart is TEPCO’s first since the 2011 Fukushima disaster and the 15th reactor brought back online in Japan under post‑Fukushima standards.
- Plans called for a gradual ramp to about 50% output within a week, a temporary inspection, and commercial operation in late February, but the timeline now depends on the investigation and regulatory confirmation.
- Kashiwazaki-Kariwa is the world’s largest nuclear plant at roughly 8.2 GW, with the No. 6 reactor at about 1.35–1.36 GW, and the resumption has faced notable local opposition, including a petition of nearly 40,000 signatures and polling showing majority resistance.