Sendai Nuclear Power Plant: Japan's First Post-Fukushima Restart
The Sendai Nuclear Power Plant (Sendai NPP) is a critical energy facility located in Satsumasendai, Kagoshima Prefecture, Japan. Operated by the Kyūshū Electric Power Company, the plant serves as a landmark in Japan's energy history, notably becoming the first nuclear facility in the country to resume operations following the nationwide shutdown triggered by the 2011 Fukushima Daiichi disaster.
The facility spans 1.45 kilometers (approximately 358 acres) and provides significant employment to the region, with 277 direct employees and an additional 790 indirect jobs. Its strategic location allows it to utilize the East China Sea as its primary cooling source.
[ไม่มีภาพประกอบ]
Key Facts
- Location: Satsumasendai, Kagoshima Prefecture, Japan.
- Operator: Kyūshū Electric Power Company.
- Reactor Type: 3-loop M type Pressurized Water Reactors (PWR).
- Total Capacity: 1780 MW (2 x 890 MW units).
- Historical Milestone: First Japanese nuclear plant to restart after the 2011 shutdown.
- Cooling Source: East China Sea.
Technical Specifications and Infrastructure
The Sendai NPP utilizes Pressurized Water Reactors (PWR)—a type of light-water reactor that keeps water under high pressure to prevent it from boiling. These specific 3-loop M type reactors were supplied and built by Mitsubishi Heavy Industries (MHI).
The site consists of two primary units, Sendai-1 and Sendai-2. Each reactor has a nameplate capacity of 890 MW and utilizes a core tonnage of 72 tons of uranium dioxide. Sendai-1 began operations on July 4, 1984, with a construction cost of 278.7 billion yen, while Sendai-2 followed on November 28, 1985, costing 228.7 billion yen.
| Feature | Details |
|---|---|
| Operational Units | 2 x 890 MW |
| Total Nameplate Capacity | 1780 MW |
| Capacity Factor | 79.7% |
| Annual Net Output | 12,427 GW·h |
| Reactor Supplier | Mitsubishi Heavy Industries (MHI) |
Safety Assessments and Stress Tests
Following the 2011 crisis, the Kyūshū Electric Power Company conducted rigorous "stress tests" to evaluate the plant's resilience. Initial reports published in December 2011 suggested the reactors could withstand seismic shocks between 945 and 1,020 gals and tsunami waves reaching 13 to 15 meters.
Between 2013 and 2014, the Japanese Nuclear Regulation Authority (NRA) introduced even stricter safety standards. To meet these, the Sendai plant implemented several enhancements:
- Seismic Upgrades: The maximum earthquake strength assumption was raised from 540 gal to 620 gal.
- Tsunami Protection: The maximum tsunami height assumption was increased from 4 meters to 5 meters, and a 10-meter-high protection wall was constructed.
- Comprehensive Planning: Design standards were updated to account for volcanic eruptions, tornadoes, and potential terrorist attacks.
To further mitigate volcanic risks, the NRA announced in 2019 the installation of seabed sensors to monitor the Aira Caldera, located 40 km from the plant. This allows for the potential removal of nuclear fuel if major volcanic activity is detected.
The Path to Restarting Operations
The process of returning to service was met with significant legal and social challenges. Despite opposition from NGOs and public figures—including former Prime Minister Naoto Kan—the NRA declared the plant safe in September 2014. After a Japanese court rejected a complaint against the restart in April 2015 and emergency plans were approved in May 2015, the plant began fuel loading.
Sendai Unit 1 officially restarted on August 11, 2015. Unit 2 followed, reaching full capacity by November 1, 2015. While Unit 1 underwent maintenance in late 2016, it resumed commercial operation on January 7, 2017.
Recent Operational Adjustments
In 2020, both reactors faced temporary shutdowns due to new anti-terrorism safety requirements. Unit 1 was shut down in March 2020 and restarted in November 2020 after completing the necessary upgrades. Unit 2 was shut down in May 2020, with a planned restart in January 2021 following similar safety installations.
Frequently Asked Questions
What makes the Sendai Nuclear Power Plant historically significant?
It was the first nuclear power plant in Japan to be restarted after the nationwide shutdown that followed the 2011 Fukushima Daiichi nuclear disaster.
What type of reactors are used at the Sendai NPP?
The plant uses two 3-loop M type Pressurized Water Reactors (PWR) supplied by Mitsubishi Heavy Industries.
How has the plant improved its safety since 2011?
Improvements include building a 10-meter-high protection wall, increasing seismic and tsunami resistance assumptions, and installing seabed sensors to monitor the nearby Aira Caldera for volcanic activity.
Why were the reactors shut down in 2020?
The reactors were temporarily shut down to implement mandatory anti-terrorism safety measures required by Japanese regulators.
Who operates the Sendai Nuclear Power Plant?
The facility is owned and operated by the Kyūshū Electric Power Company.