Including severe accidents in the design basis of nuclear power plants: An organizational factors perspective after the Fukushima accident

• The Fukushima accident was man-made and not caused by natural phenomena.
• Vulnerabilities were known by regulator and licensee but measures were not taken.
• There was lack of independence and transparency of the regulatory body.
• Laws and regulations have not been updated to international standards.
• Organizational failures have played an important role in the Fukushima accident.

The Fukushima accident was clearly an accident made by humans and not caused by natural phenomena as was initially thought. Vulnerabilities were known by both regulators and operator but they postponed measures. The emergency plan was not effective in protecting the public, because the involved parties were not sufficiently prepared to make the right decisions. The shortcomings and faults mentioned above resulted from the lack of independence and transparency of the regulatory body. Even laws and regulations, and technical standards, have not been upgraded to international standards. Regulators have not defined requirements and left for the operator to decide what would be more appropriate. In this aspect, there was clearly a lack of independence between these bodies and operator’s lobby power. The above situation raised the question of urgent updating of institutions, in particular those responsible for nuclear safety. The above evidences show that several nuclear safety principles were not followed. This paper intends to highlight some existing safety criteria that were developed from the operational experience of the severe accidents that occurred at TMI and Chernobyl that should be incorporated in the design of new nuclear power plants and to provide appropriate design changes (backfittings) for reactors that belong to the previous generation prior to the occurrence of these accidents, through the study of design vulnerabilities. Furthermore, the main criteria that define an effective regulatory agency are also discussed. Although these criteria appear in IAEA guides and requirements, this paper proposes that some of these requirements should be more detailed in line with what has been learned as the most important lessons of Fukushima in order to prevent organizational failures.