Tokyo Electric Power Company Holdings Inc. (TEPCO) on Wednesday, January 21, 2026, successfully restarted Reactor No. 6 at the Kashiwazaki-Kariwa nuclear power plant in Niigata Prefecture, marking the facility's first reactor reactivation and TEPCO's first operational restart of any nuclear unit since the catastrophic Fukushima Daiichi accident in March 2011.
The 1.36-gigawatt boiling water reactor (BWR) was brought online at 19:02 local time (11:02 GMT) after TEPCO completed final inspections and reported to the Nuclear Regulation Authority (NRA) that issues with a control-rod alarm had been fully resolved. The restart process had been delayed by one day from the originally planned Tuesday, January 20, due to a malfunction detected during pre-startup testing involving alarm settings for 88 of the reactor's 205 control rods, which are essential for suppressing nuclear fission reactions. TEPCO confirmed the fault—a setting error—was corrected by early Wednesday morning, allowing the withdrawal of control rods and initiation of criticality.
Kashiwazaki-Kariwa, with seven reactors and a total capacity of 8.2 gigawatts when fully operational, remains the world's largest nuclear power station by installed capacity. All units have been idle since a routine inspection in 2012, prompted by heightened public safety concerns and regulatory scrutiny following the Fukushima meltdown. That disaster—triggered by a massive earthquake and tsunami—led to core meltdowns in three reactors at Fukushima Daiichi, widespread radioactive contamination, and the evacuation of over 150,000 people. It prompted Japan to shut down all 54 operable reactors nationwide for safety reviews.
The Kashiwazaki-Kariwa plant shares the same BWR design as Fukushima Daiichi and is operated by the same utility, TEPCO, factors that fueled skepticism about the company's ability to manage such facilities safely. Post-Fukushima reforms introduced stringent safety standards, including enhanced tsunami defenses, seismic reinforcements, anti-terrorism measures, and improved emergency preparedness. The NRA granted approval for restarts at Kashiwazaki-Kariwa Units 6 and 7 in December 2023 after rigorous assessments, though only Unit 6 has advanced to this stage. Unit 7's restart is tentatively targeted for around 2030, while the future of Units 1–5 remains uncertain, with potential decommissioning under consideration.
This reactivation brings the total number of restarted reactors in Japan to 15 out of 33 that remain operable following post-Fukushima safety upgrades. Japan's government, under Prime Minister Shigeru Ishiba's administration, has prioritized maximizing nuclear utilization to ensure energy security, reduce reliance on imported fossil fuels, and meet ambitious decarbonization targets amid rising electricity demand from data centers, semiconductor manufacturing, and electrification efforts.
The restart is expected to bolster power supply to the Tokyo metropolitan area—Japan's most populous and economically vital region—once Unit 6 reaches commercial operation by the end of February 2026. After achieving 50% power output in about a week, the reactor will undergo a temporary shutdown for further inspections (likely late January to early February), followed by gradual ramp-up to full capacity. TEPCO estimates the unit could supply electricity equivalent to powering millions of households.
Public opinion remains deeply divided. In Niigata Prefecture and nearby communities, residents express mixed views: some welcome the economic benefits, including job creation, local tax revenue, and revitalization of the regional economy, while others harbor persistent fears over safety, evacuation planning, and the risk of another major incident. Local protests and petitions have highlighted concerns about TEPCO's track record, including past data falsification scandals and ongoing Fukushima decommissioning challenges. Niigata Governor Hideyo Hanazumi approved the restart in late 2025 after consultations, but emphasized continuous monitoring and transparency.
The NRA and TEPCO have stressed that the plant now incorporates world-class safety enhancements, such as elevated seawalls, additional backup power systems, filtered vent installations, and rigorous staff training. International observers, including the International Atomic Energy Agency (IAEA), have reviewed Japan's post-Fukushima framework positively, though they continue to advocate for sustained vigilance.
This development signals a cautious but determined revival of Japan's nuclear sector, which once provided about 30% of the nation's electricity before 2011. Post-accident, nuclear's share plummeted to near zero, forcing greater dependence on liquefied natural gas, coal, and renewables. With energy prices volatile and climate goals pressing, the government aims to raise nuclear's contribution to 20–22% by 2030.
For TEPCO, the Kashiwazaki-Kariwa restart is pivotal for financial recovery. The utility has shouldered massive costs from Fukushima cleanup (estimated at trillions of yen) and compensation, compounded by years of idled assets. Successful operation could improve profitability and restore investor confidence, though full plant reactivation remains years away.
As Japan navigates its nuclear future, the Kashiwazaki-Kariwa milestone underscores the tension between energy needs, technological advancements, and enduring public trauma from Fukushima. Close scrutiny from regulators, local communities, and the international community will accompany every step of Unit 6's operation, with implications for broader restarts and Japan's energy transition strategy.
