"It was a profoundly man-made disaster -- that could and should have been foreseen and prevented," said Kiyoshi Kurokawa, chairman of the Fukushima Nuclear Accident Independent Investigation Commission in the introduction of its 641-page report on the worst nuclear crisis since the 1986 Chernobyl disaster in Ukraine.
"And its effects could have been mitigated by a more effective human response," added Kurokawa, who is a former president of the Science Council of Japan.
The commission's findings confirm that the tremors caused by the March 11, 2011, earthquake were powerful enough to cause damage and that seismic checks to the reactors, ordered before the disaster, had not been conducted.
Plant operator Tokyo Electric Power Co., on the contrary, has said that the plant withstood the earthquake unharmed but was affected by the ensuing massive tsunami.
The report states that "it is impossible to limit the direct cause of the accident to the tsunami without substantive evidence." Putting all the blame on the "unexpected" tsunami rather than "on the more foreseeable quake," the authors said, "is an attempt to avoid responsibility."
The commission's report was based on more than 900 hours of hearings and interviews with 1,167 people involved in the Fukushima disaster response.
The report quotes Masao Yoshida, then chief of the crippled nuclear power plant, as saying "the chain of command was a total mess."
The authors were critical of the excessive level of involvement of then Prime Minister Naoto Kan and his office.
"The direct intervention by the [prime minister's office] ... disrupted the chain of command and brought disorder to an already dire situation" at the nuclear power plant, the report states.
The report said that while Tepco headquarters was supposed to provide support to the Fukushima facility, "in reality it became subordinate to the [prime minister's office], and ended up simply relaying the [prime minister's office's] intentions."
Yet the report concluded that Tepco was not a victim of excessive intervention by the prime minister's office, but had instead invited it.
The report says the Fukushima disaster "was the result of collusion between the government, the regulators and Tepco, and the lack of governance by said parties ... we conclude that the accident was clearly 'man-made.' "
Commission chief Kurokawa, in presenting the report, told reporters, "The crisis is not yet over. I believe that Japan must take steps toward realizing the commission's proposals to regain the world's trust," he said.