BERLIN – The widespread assumption that nuclear plants were safe was behind the March 2011 accident at the Fukushima No. 1 nuclear plant, the International Atomic Energy Agency said in its final report on the crisis.
Before the catastrophe, “there was a basic assumption in Japan that the design of nuclear power plants and the safety measures that had been put in place were sufficiently robust to withstand external events of low probability and high consequences,” the report, released Monday, says.
Because of this assumption, “there was a tendency for organizations and their staff not to challenge the level of safety,” the report says. This “resulted in a situation where safety improvements were not introduced promptly.”
The IAEA report stresses the need to “take an integrated approach that takes account of the complex interactions between people, organizations and technology” in order to better identify plant vulnerabilities to natural disasters and other unexpected events.
The report was compiled by around 180 experts from 42 countries. The plant was damaged in the tsunami caused by the powerful earthquake that hit off the Tohoku coast on March 11, 2011.
Some of the factors that contributed to the accident were “not unique to Japan,” IAEA Director General Yukiya Amano says in the report, adding that “continuous questioning and openness to learning from experience are key to safety culture and are essential for everyone involved in nuclear power.”
The Fukushima No. 1 plant’s vulnerability “to external hazards had not been reassessed in a systematic and comprehensive manner during its lifetime,” the IAEA report says.
“The assessment of natural hazards needs to consider the potential for their occurrence in combination, either simultaneously or sequentially,” it says.
Tokyo Electric Power Co. was “not fully prepared for the multiunit loss of power and the loss of cooling caused by the tsunami.”
“Operators had therefore not received appropriate training and had not taken part in relevant severe accident exercises, and the equipment available to them was not adequate in the degraded plant conditions,” the report says.
Furthermore, the report argues that “it was not fully clear which organizations had the responsibility and authority to issue binding instructions on how to respond to safety issues without delay.”
It points to a lack of “coordinated arrangements for responding to a nuclear emergency and a natural disaster occurring simultaneously.”
On the accident’s effects on human health, the Vienna-based IAEA said that thyroid cancer in children is “the most likely health effect.”
However, it adds that “because the reported thyroid doses attributable to the accident were generally low, an increase in childhood thyroid cancer attributable to the accident is unlikely.”
Still, the report notes that uncertainties remain “concerning the thyroid equivalent doses incurred by children immediately after the accident.”
As for the return home of people who have been evacuated following the accident, the IAEA stressed the need to consider “factors such as the restoration of infrastructure, and the viability and sustainable economic activity of the community.”
The long-term goal of post-accident recovery is to re-establish an acceptable basis for a fully functioning society in areas affected by the nuclear crisis, the report notes.
“Communication with the public on recovery activities is essential to build trust,” it says. For effective communication, “it is necessary for experts to understand the information needs of the affected population and to provide understandable information through relevant means.”