Tokyo Electric Power Co. Announces Partial Restart of the Kashiwazaki‑Kariwa Nuclear Plant
Tokyo Electric Power Co. Holdings Inc. (TEPCO) confirmed that the first unit of its Kashiwazaki‑Kariwa nuclear power plant, the largest nuclear facility in the world, will resume operation on 20 January 2026. The announcement came during a press briefing held in Tokyo on 24 December 2025, in which President Tomiaki Kobayakawa outlined the technical and regulatory steps that led to the decision.
Background of the Kashiwazaki‑Kariwa Site
The Kashiwazaki‑Kariwa complex, located in Niigata Prefecture, hosts four nuclear reactors built between 1973 and 1995. After the Fukushima‑Daiichi disaster in 2011, all reactors were permanently shut down and the plant’s status changed from “operational” to “decommissioned.” The site has since become a focal point in Japan’s broader strategy to re‑integrate nuclear power into the national grid, balancing energy security with stringent safety standards.
The plant’s first unit, which has a capacity of approximately 1,260 MW, was the first to be restarted in the post‑Fukushima era. Its reactivation marked a milestone for TEPCO and the Japanese government, demonstrating that the country can maintain its nuclear supply chain while addressing public concerns about safety.
Regulatory Pathway
The restart was authorized by the Ministry of Economy, Trade and Industry (METI) after TEPCO submitted a comprehensive safety review and remediation plan. Key components of the plan included:
| Component | Description |
|---|---|
| Structural Integrity | Detailed seismic testing and reinforcement of critical containment structures to meet updated earthquake‑resilience standards. |
| Radiological Monitoring | Installation of advanced radiation‑detector arrays and real‑time data‑analysis systems to detect any anomalous releases. |
| Emergency Response | Updated evacuation drills, community engagement programs, and coordination with local prefectural emergency services. |
| Operational Oversight | Introduction of a dual‑control system, with independent operators monitoring critical processes. |
The Ministry’s approval was contingent upon a public consultation period, during which community representatives and industry experts provided feedback. The consultation concluded on 15 December 2025, with the majority of concerns addressed.
Implications for TEPCO’s Energy Portfolio
TEPCO’s decision to restart the Kashiwazaki‑Kariwa unit aligns with its broader energy mix strategy. The company operates across hydroelectric, thermal, and nuclear segments and also offers information‑communication services in the Kanto region. Re‑activating the plant will:
- Increase Baseload Generation – The 1,260 MW capacity will provide a stable, low‑carbon power supply that complements renewable sources and helps mitigate grid fluctuations.
- Support Carbon‑Neutral Targets – By reducing dependence on fossil‑fuel‑based thermal units, TEPCO can advance Japan’s commitments to net‑zero emissions by 2050.
- Enhance Economic Stability – Nuclear power contributes to a predictable energy cost structure, benefiting both commercial customers and the broader Japanese economy.
Financially, TEPCO’s market presence is reflected in a market cap of ¥1.065 × 10¹² and a closing share price of ¥665 as of 22 December 2025. While the plant’s restart may involve short‑term capital outlays, the long‑term revenue from sustained nuclear output is expected to strengthen the company’s dividend prospects and shareholder value.
Market Reception
The announcement was met with cautious optimism in financial markets. TEPCO’s shares experienced a modest uptick in the early trading session on 24 December, reflecting investor confidence in the regulatory clearance and the company’s management of safety protocols. Analysts noted that the restart could serve as a benchmark for other utilities contemplating nuclear revival, potentially stimulating broader discussions on energy policy across Asia.
Looking Ahead
TEPCO’s next steps include initiating the final commissioning tests, which will be conducted in collaboration with the Japan Nuclear Safety Commission. The plant’s first unit is slated to go online by 20 January 2026, after which TEPCO plans to reassess the feasibility of restarting additional reactors at the site in alignment with national energy objectives.
By moving forward with the Kashiwazaki‑Kariwa restart, Tokyo Electric Power Co. demonstrates a commitment to balancing rigorous safety standards with the imperative of sustaining Japan’s energy supply in a post‑Fukushima era.
