Experts Consider Fukushima Accident Causes

Denis Flory, IAEA Deputy Director General, Department of Nuclear Safety and Security, addressing participants at the meeting. (Photo: D. Calma/IAEA)

At the IAEA headquarters in Vienna, around 250 experts, representing 50 Member States and other relevant organisations, are discussing the root causes of the accident at TEPCO's Fukushima Daiichi Nuclear Power Plant, focussing on reactor and spent fuel management safety. The IAEA organized this meeting as a part of the Action Plan on Nuclear Safety that provides a comprehensive programme and all nuclear safety tools to systematically strengthen the global nuclear safety framework at the national, regional and international levels.

The experts from the IAEA Member States' utilities, research and design organizations, regulatory organizations, manufacturing and service companies and other stakeholders are analysing all technical aspects of reactor and spent nuclear fuel management safety and performance related to severe accidents in the light of the Fukushima Daiichi accident.

Culture of Constant Vigilance

At the meeting's opening on Monday, 19 March 2012, Denis Flory, IAEA Deputy Director General of the Department of Nuclear Safety and Security, said that significant progress has been made to strengthen nuclear safety worldwide, and to make nuclear energy safer, noting that many Member States have taken steps to assess the safety vulnerabilities of their nuclear power plants and to introduce necessary improvements. He reiterated the IAEA Director General's call for "a culture of constant vigilance and improvement" and warned that "complacency can kill."

Regulatory Independence

Flory emphasized that the independence of regulatory bodies has been recognised as "a foundation stone of nuclear safety," and that "regulatory bodies must have the necessary authority, competence and resources to discharge their regulatory mandate." Some Member States are now in the process of answering the weaknesses identified in this field.

Compliance with Safety Standards

Flory said that expert reviews of the accident highlight the clear need for a global nuclear safety framework and the effective implementation of the IAEA safety standards to provide the basis for a high level of safety.

Among other lessons learned, plant design and severe accident management procedures need to be consistent with the IAEA Safety Standards. The nuclear safety culture that informs regulators and operators actions should be sufficiently developed "to acknowledge critical safety problems and related international developments and experience."

Vulnerabilities Related To Extreme Hazards

In the light of the Fukushima accident, Flory said that the "design basis for a nuclear power plant can no longer be taken for granted." He emphasised the need for the close relation "that should exist between science, safety assessment and safety regulation."

Severe Accident Management

The Fukushima accident demonstrates how earthquakes and floods can combine, leading to prolonged power loss and the total loss of the heat sink. These events may be compounded by human error, further impairing the operator's accident management capability. Flory recommended that future plant safety assessments should consider site flooding and the subsequent complete and prolonged loss of power among the severe accident scenarios.

During the Fukushima Daiichi accident, the plant operators had no reliable instrumentation to monitor essential safety parameters such as the reactor temperature and coolant level. Flory identified "a need for updated principles for accident monitoring instrumentation," as a basis for developing national and international standards.

Since the countermeasures to alleviate the severe accident's consequences had not adequately prepared the plant to respond without significant damage, Flory advised that the Severe Accident Management Guides must be enhanced to deal with extreme events in the presence of severely damaged infrastructure.

Emergency Preparedness and Response

The IAEA Safety Standards for emergency preparedness and response at the national level are crucial, Flory said, since "they improve preparedness and response, facilitate communication in an emergency and contribute to the harmonization of national criteria for protective actions."

Information-sharing

Sharing and distributing information is one of the IAEA's essential tasks during a nuclear emergency. The IAEA's formal role in information-sharing resulted from decisions taken in the wake of the 1986 Chernobyl accident, Flory said. This role was largely limited to distributing information validated by the State that suffered the accident. He highlighted the fact that "in an era of instant communication, the Fukushima accident demonstrated the need for a stronger role of the IAEA to meet the expectations of Member States and the public."

In conclusion, Flory urged all nuclear regulators, plant operators, governments or international organisations, "to maintain the momentum gained over the last 12 months in our collective drive to improve nuclear safety around the world."

This International Experts Meeting is chaired by Richard Meserve, chairman of the International Nuclear Safety Group and president of the Carnegie Institution for Science, and co-chaired by Jacques Repussard, Director General of the French Institut de Radioprotection et Sureté Nucléaire, and S.K. Chande, Vice Chairman of the Atomic Energy Regulatory Board of India.

Last update: 18 November 2014