Fukushima Daini Nuclear Power Plant (Fukushima II)

Site, design and suppliers

Fukushima Daini uses boiling water reactor (BWR) technology. The facility includes reactor pressure vessels, containment structures, turbine buildings and multiple safety system layers designed for normal operation and emergency cooling. Major Japanese engineering firms supplied the reactor units: reactors 1 and 3 were built with components from Toshiba, while reactors 2 and 4 were built with contributions from Hitachi. Technical and regulatory documentation for the site is maintained by local and national authorities in Fukushima Prefecture and Japan.

Reactors and safety systems

The plant's four reactor units are equipped with multiple redundant safety subsystems, including control rod insertion and emergency core cooling. Automatic shutdown systems activate to halt fission on detection of abnormal seismic or operational conditions; these systems were a key factor during events in 2011 (automatic shutdown systems).

2011 earthquake, tsunami and immediate response

All four reactors at Fukushima Daini automatically shut down following the 2011 Tōhoku earthquake and tsunami. Operators and emergency teams worked to stabilize reactors and maintain cooling; authorities reported that the units reached cold shutdown conditions within days, helping to prevent the level of core damage that occurred at the nearby Fukushima Daiichi site. The sequence of actions and the wider natural disaster context are documented in reports on the 2011 earthquake and tsunami.

Contaminated water, environmental concerns and fisheries

Tsunami flooding introduced seawater into plant structures. TEPCO reported that several thousand tons of seawater and accumulated water remained onsite after the tsunami, and a portion contained detectable radioactive isotopes. Proposals to discharge treated or uncontaminated water were reviewed amid concerns from local fishing communities and regulatory authorities; the incident highlighted tensions among emergency response, environmental monitoring, and protection of local fisheries.

Post-2011 operations, remediation and decommissioning

National and company statements indicated that the acute nuclear emergency at Fukushima Daini was declared over in late 2011, after on-site activities had stabilized reactor conditions. Since then, the units have remained offline and subject to long-term tasks including fuel management, decontamination of affected areas, environmental monitoring and planning for decommissioning. Oversight and technical work involve TEPCO, national regulators and local authorities; more detailed reactor unit information is available in technical summaries (reactor information).

Distinctions and legacy

• Proximity but distinction: Fukushima Daini is a separate installation from the more widely publicized Fukushima Daiichi site; the two complexes are operated independently but are relatively close geographically.
• Performance under stress: Emergency systems at Daini achieved stable shutdowns that limited core damage; this performance is often cited in comparative analyses of the 2011 nuclear responses.
• Long-term community impact: The plant’s post-accident management continues to affect local recovery, fisheries and planning for decommissioning, illustrating the intersection of technical, environmental and social issues.

For authoritative and current operational records, consult official operator and government publications. Further technical background and local information can be found via TEPCO materials (TEPCO), prefectural resources (Fukushima Prefecture) and manufacturer reports from Toshiba and Hitachi. See the plant overview (overview) and reactor details (details) for additional reading.

Note: This article summarizes widely reported facts about Fukushima Daini and its situation following the 2011 disaster. For precise operational data, regulatory filings and the latest status, consult official documents and regulatory updates.