The investigation committee on the accident at the Fukushima I nuclear power stations of Tokyo Electric Power Company (TEPCO) set up by the Japanese government compiled its final report on July 23. Contrary to the final report released previously by the Fukushima Nuclear Accident Independent Investigation Commission set up by the National Diet, which pointed out the possibility that the piping of Fukushima I unit 1 may have been damaged by the earthquake before the tsunami hit. The government-appointed investigation panel recently concluded that the piping suffered no major damage from the earthquake and the nuclear accident was caused by the subsequent tsunami.
This conclusion was reached after estimating the pressure inside the containment vessel on the hypothesis that damaged piping was leaking steam, and comparing the calculation results with the values actually measured at the site. The comparison revealed a significant difference between the estimated and actual values.
The National Diet’s investigation panel, however, had argued based on the testimony obtained from workers at the accident site that steam was leaking from the piping immediately after the earthquake. While the two panels are presenting conflicting accounts of the accident, it is difficult to verify which of the two reports explains what really happened at the site.
Meanwhile, the two sides’ views are in alignment in that the excessive intervention by then prime minister Naoto Kan and his office posed a hindrance to emergency response efforts at the site.
The government’s investigation panel was instituted in May last year, and it has interviewed 722 individuals to date. It issued an interim report in December last year and has since been examining issues that required further investigation or analysis. Yotaro Hatamura, the panel’s chair, held a press conference on July 23 and made an objection against the National Diet’s investigation panel for asserting that the Fukushima I accident was a “man-made disaster” [resulting from the negligence of TEPCO that failed to take sufficient measures against severe accidents].
Hatamura said, “Although labeling the accident as man-made provides an easy clarification, making such a conclusion prematurely could be dangerous. If we narrowly conclude that it was merely a man-made disaster, it may blind us to other factors.”
