The parameters set for tsunami flood protection at the Fukushima Daiichi site were ‘inadequate’ and eventually led to the loss of all practical cooling paths for the reactors, a new report from the Electric Power Research Institute has concluded.
The EPRI report, released 10 April, examines the underlying technical factors that lead to the loss of critical systems at the Fukushima Daiichi reactors following the earthquake and tsunami in Japan on 11 March 2011.
The report reviews the plant’s design basis for seismic and tsunami events, examines its response capabilities with respect to seismic and tsunami events, and then compares the plant’s design capabilities with the actual events in March 2011.
The analysis traced the flooding and submergence to the significant difference between the tsunami height the plant was designed for and the one that impacted the plant. “That difference limited the ability of tsunami protection and mitigation measures to effectively address the event,” EPRI said.
The plant’s primary tsunami protection strategy consisted of locating critical equipment above the design tsunami height. EPRI also found that in establishing a maximum tsunami height that might impact the plant, the Japanese design method did not factor in multiple geological fault ruptures.
Many of the findings of the EPRI report, released 10 April, echo those in other post-Fukushima analyses that were published around the first anniversary for the accident (see May 2012 print issue; soon to be published)