Title: Nuclear Resurgence Amid Safety Concerns: The Case of TEPCO’s Kashiwazaki-Kariwa Unit 6 Restart and Immediate Suspension in January 2026
Abstract
On January 21, 2026, Tokyo Electric Power Company Holdings (TEPCO) restarted Unit 6 at the Kashiwazaki-Kariwa Nuclear Power Plant—the first reactor reactivated by the utility since the 2011 Fukushima Daiichi nuclear disaster. However, within hours, operations were suspended after an alarm was triggered during control rod withdrawal, reigniting public and regulatory scrutiny over Japan’s nuclear renaissance. This paper examines the technical, institutional, and socio-political dimensions of this event, analyzing the implications for Japan’s energy policy, nuclear safety culture, and public trust in post-Fukushima governance. Drawing on regulatory statements, technical reports, and media coverage, the study highlights the fragility of nuclear restart programs in seismically active countries with complex stakeholder landscapes. The incident underscores persistent challenges in operational discipline, technological reliability, and institutional accountability—critical factors for any nation pursuing nuclear energy as a climate and energy security solution.
Keywords: Nuclear energy, TEPCO, Kashiwazaki-Kariwa, Fukushima, control rods, nuclear safety, Japan energy policy, nuclear regulation, post-Fukushima Japan
- Introduction
The restart of Unit 6 at the Kashiwazaki-Kariwa Nuclear Power Plant (KK-NPP) on January 21, 2026, marked a symbolic milestone in Japan’s gradual return to nuclear energy following the Fukushima Daiichi catastrophe of March 2011. For Tokyo Electric Power Company (TEPCO), the operator of both Fukushima and Kashiwazaki-Kariwa, this was the first successful reactor restart in over a decade—a key development in the company’s ongoing rehabilitation and Japan’s broader decarbonization strategy. However, less than 24 hours later, on January 22, TEPCO suspended operations after an alarm activated during control rod withdrawal, raising immediate concerns about operational readiness, equipment integrity, and long-term safety culture.
This paper contextualizes the technical failure within Japan’s nuclear reactivation program, evaluating the regulatory, technical, and public trust challenges facing TEPCO and the Nuclear Regulation Authority (NRA). It argues that while nuclear energy remains a strategic component of Japan’s energy mix, recurrent technical hiccups—especially in historically problematic facilities—threaten the credibility of the restart process. By analyzing the January 2026 incident, the study provides insights into the tension between energy policy imperatives and the enduring legacy of systemic failures in Japan’s nuclear industry.
- Background: The Fukushima Disaster and Japan’s Nuclear Policy Shift
The Fukushima Daiichi nuclear disaster, triggered by the Tōhoku earthquake and tsunami on March 11, 2011, led to the meltdown of three reactors at the Fukushima plant operated by TEPCO. The event resulted in widespread radioactive contamination, mass evacuations, long-term health and environmental impacts, and the collapse of public confidence in nuclear energy.
In the aftermath, Japan shut down all 54 of its nuclear reactors. By 2012, nuclear power contributed less than 1% of national electricity, compared to around 30% in 2010. The government established the independent Nuclear Regulation Authority (NRA) in 2012 to replace the discredited Nuclear and Industrial Safety Agency (NISA), introducing stringent new safety standards requiring protection against severe earthquakes, tsunamis, terrorism, and other extreme events.
Despite political vacillation across successive administrations, post-2020 Japan has pursued a nuclear reactivation strategy. The 2022 Strategic Energy Plan reaffirmed nuclear energy as a “stable base-load power source” essential for achieving carbon neutrality by 2050, planning for reactors to supply 20–22% of electricity by 2030. As of early 2026, 12 reactors across 7 plants had been restarted, with dozens more undergoing safety reviews.
- The Kashiwazaki-Kariwa Plant: A Troubled Legacy
The Kashiwazaki-Kariwa Nuclear Power Plant in Niigata Prefecture, about 220 km northwest of Tokyo, is the largest nuclear power station in the world by net electrical capacity (7,965 MW across seven units). Operated by TEPCO, the plant has been offline since 2011, with all units suspended indefinitely due to safety concerns and local opposition.
The site has a history of operational and safety failures:
In 2007, a magnitude 6.6 earthquake (the Niigata-Chuetsu-Oki earthquake) caused fires, radiation leaks, and structural damage, revealing inadequate seismic preparedness.
Multiple safety violations were uncovered over the years, including falsified inspection records and poor crisis management protocols.
In 2017, the NRA denied restart approvals due to insufficient anti-terrorism measures and safety culture deficiencies.
Despite these setbacks, TEPCO and the national government have pushed for the restart of Units 6 and 7 (both Advanced Boiling Water Reactors, or ABWRs) as flagship projects in the nuclear comeback. Niigata Prefecture, traditionally cautious, granted conditional approval for restarts in 2023, contingent on rigorous safety demonstrations and emergency preparedness.
- The January 2026 Restart: Technical Sequence and Immediate Failure
4.1. Reactivation Timeline
January 20, 2026: Final pre-startup tests began.
January 21, 19:02 JST: Unit 6 was reactivated, marking the first reactor restart by TEPCO since Fukushima.
20:30 JST (approx.): The reactor achieved criticality, indicating the initiation of a self-sustaining nuclear chain reaction.
January 22, 00:28 JST: An alarm triggered during the withdrawal of control rods—a crucial step in increasing reactor power output.
Control rods, typically made of neutron-absorbing materials (e.g., boron or hafnium), regulate the rate of fission by absorbing neutrons in the reactor core. Their precise and synchronized movement is essential for safe reactor startup and load-following operations.
4.2. Nature of the Incident
According to TEPCO, the alarm was set off due to an anomaly in the “equipment to manoeuvre the control rods”—likely related to the drive mechanism or position detection system. The system failed to confirm expected rod positions, prompting automatic safety protocols to halt further withdrawal.
The plant remained in a subcritical state after the alarm, with no release of radiation detected. The NRA confirmed that the reactor was stable and posed no immediate safety risk. No abnormal radiation levels were reported in surrounding areas, including monitoring posts operated by the Niigata Prefectural Government.
Nonetheless, TEPCO suspended all control rod operations and initiated an investigation into the root cause, including a review of equipment logs, maintenance records, and software interfaces.
- Technical and Human Factors: A Multilayered Failure?
While the immediate shutdown was a success of the fail-safe design, the incident raises deeper questions about the technical and organizational readiness of TEPCO.
5.1. Equipment Reliability
The control rod drive mechanism (CRDM) is a high-precision electromechanical system. Failures can stem from:
Degradation due to long-term disuse (Unit 6 had been offline since 2011).
Inadequate testing of backup systems.
Software or sensor calibration errors in digital control systems.
Given the 15-year dormancy of the reactor, latent equipment weaknesses are plausible. Other Japanese reactors that underwent long-term shutdowns (e.g., Mihama Unit 3) also experienced technical glitches upon restart.
5.2. Organizational and Safety Culture Issues
TEPCO has historically struggled with a weak safety culture, including:
Suppression of dissenting opinions.
Inadequate training and oversight.
A hierarchical structure that discouraged reporting of anomalies.
Although reforms have been mandated since 2011, the 2026 incident echoes past failures. The timing—just hours after restart—is emblematic of residual flaws in operational discipline. Moreover, the initial delay in restart (January 21 instead of 20) due to a prior control rod alarm suggests unresolved technical vulnerabilities.
The NRA has repeatedly warned TEPCO about insufficient progress in reforming safety culture. In 2023, it cited TEPCO for failing to fully implement recommendations from external review panels. This context strengthens concerns that technical failures may reflect deeper institutional pathologies.
- Regulatory Oversight and Public Response
6.1. NRA’s Role and Response
The Nuclear Regulation Authority responded promptly, confirming that safety systems functioned as designed and no radiation exposure occurred. However, it emphasized the need for TEPCO to conduct a thorough investigation and report findings transparently.
The NRA has maintained a strict posture since Fukushima, denying restart approvals for reactors with unresolved safety issues. Nevertheless, critics argue that the regulator may be under political pressure to approve restarts as part of national energy goals—a phenomenon known as “regulatory capture” risk.
6.2. Public and Local Reactions
Public opinion in Japan remains divided on nuclear energy. A 2025 NHK survey found that 49% of respondents opposed nuclear restarts, while 37% supported them—indicating persistent public skepticism.
In Niigata, local residents and anti-nuclear groups condemned the incident as proof of TEPCO’s unreliability. Governor Hideyo Hanazumi, who approved the restart under strict conditions, called for full transparency and urged TEPCO to prioritize safety over schedule.
The proximity of the Kashiwazaki-Kariwa plant to active seismic zones amplifies fears. Japan lies within the Pacific Ring of Fire, with high tectonic activity. Critics argue that restarting reactors in such regions—especially those with prior earthquake damage—remains inherently risky.
- Policy Implications for Japan’s Nuclear Energy Strategy
The January 2026 incident at Kashiwazaki-Kariwa has significant implications for Japan’s nuclear ambitions:
7.1. Energy Security and Decarbonization
Japan imports over 88% of its energy, making it highly vulnerable to global fuel price volatility and supply disruptions. With liquefied natural gas (LNG), coal, and oil still dominating the mix, energy costs remain high. Nuclear energy offers a low-carbon, domestically managed alternative critical to achieving Japan’s 2050 net-zero target.
However, the delayed and troubled restarts undermine confidence in nuclear as a reliable baseload. As of 2026, nuclear contributes only ~7% to electricity generation. Further setbacks could force Japan to extend fossil fuel use or accelerate renewable deployment—both costly and technically challenging.
7.2. Impact on Restart Pipeline
The Kashiwazaki-Kariwa incident may delay the approval of other idle reactors. Units 7 at Kashiwazaki-Kariwa, as well as reactors at Hamaoka and Tsuruga, face similar scrutiny. Regulators may impose additional requirements, including enhanced control system testing and longer dry-run simulations.
Furthermore, the incident may strengthen legal challenges from citizen groups. Since 2011, multiple restarts have been halted by court injunctions citing insufficient safety assessments.
- Comparative Perspectives: Lessons from Global Nuclear Programs
Japan’s experience contrasts with global trends. France and the UK are pursuing nuclear expansion with new EPR reactors. China has over 25 reactors under construction, emphasizing rapid deployment. South Korea has reversed its anti-nuclear policy, restarting reactors and exporting technology.
Yet these programs also face challenges:
France’s Flamanville EPR has experienced decade-long delays and cost overruns.
South Korea faced a 2013 scandal involving counterfeit parts in nuclear plants.
The U.S. sees limited new construction due to high costs and regulatory hurdles.
What distinguishes Japan is the combination of severe natural hazards, a powerful anti-nuclear civil society, and a utility with a tarnished operational record. As such, trust-building is as critical as technical compliance.
- Conclusion
The brief restart and immediate suspension of TEPCO’s Kashiwazaki-Kariwa Unit 6 in January 2026 symbolize both progress and persistent vulnerability in Japan’s post-Fukushima nuclear renaissance. While the safe shutdown response reflects improvements in safety engineering, the triggering of a control rod alarm—twice in two days—reveals unresolved technical and organizational weaknesses.
For Japan to realize its nuclear energy goals, TEPCO must demonstrate not only technical proficiency but also cultural transformation. The incident underscores the need for:
Rigorous testing of dormant systems.
Transparent failure investigations.
Continuous investment in human and institutional capacity.
Moreover, policymakers must balance energy needs with societal trust. Rapid restarts driven by political or economic urgency risk repeating the complacency that led to Fukushima. The roadmap to nuclear revival must be guided not by timelines, but by unwavering adherence to safety-first principles.
As Asia’s energy landscape evolves—with rising demand, climate pressures, and geopolitical uncertainty—Japan’s nuclear journey offers cautionary lessons for any nation navigating the complex trade-offs of high-stakes energy transitions.
References
Tokyo Electric Power Company Holdings (TEPCO). (2026). Press Release: Status Update on Kashiwazaki-Kariwa Nuclear Power Station Unit 6. January 22, 2026.
Nuclear Regulation Authority (NRA), Japan. (2026). Statement on Kashiwazaki-Kariwa Unit 6 Incident. January 22, 2026.
NHK. (2025). Public Opinion Survey on Nuclear Power in Japan.
Ministry of Economy, Trade and Industry (METI). (2022). Strategic Energy Plan.
International Atomic Energy Agency (IAEA). (2015). The Fukushima Daiichi Accident: Technical Summary.
World Nuclear Association. (2025). Nuclear Power in Japan.
Asahi Shimbun. (2026). “Kashiwazaki-Kariwa restart halted by alarm.” Asahi Shimbun Online, January 22, 2026.
Reuters. (2026). “TEPCO shuts reactor after alarm, a day after restart.” Reuters News, January 22, 2026.
BBC News. (2011). Japan’s nuclear crisis: timeline.
OECD Nuclear Energy Agency. (2023). Safety Culture in Nuclear Installations: Guidance and Practices.
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