The Electric Power Research Institute (EPRI) released a report April 10 that examines the underlying technical factors leading to the loss of critical systems at the Fukushima Daiichi reactors following the earthquake and tsunami in Japan in March 2011.
The report found that parameters set for tsunami flood protection were inadequate, which led to the eventual loss of all cooling paths for the reactors and loss of access to off-site alternate current power due to the submergence of backup power and distribution systems. Also, backup DC power was lost due to the submergence of electrical distribution systems and the depletion of power stored in batteries.
The analysis traced the flooding and submergence to the difference between the tsunami height the plant was designed for and the one that impacted the plant. The plant’s primary tsunami protection strategy consisted of locating critical equipment above the design tsunami height. In establishing a maximum tsunami height that might impact the generating station, the Japanese design method did not factor in multiple geological fault ruptures.
The report’s results were based on event information, incident timelines, plant design features, and regulatory and design code requirements.
Click here to download the full report (PDF).
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