On 22 March 2012, international experts concluded their meeting at the IAEA headquarters in Vienna. In their presentations and discussions, the experts sought to identify the root causes of the accident at TEPCO’s Fukushima Daiichi Nuclear Power Plant.
Over 230 experts from 44 IAEA Member States and four international organizations undertook wide-ranging and open discussion to analyze all the relevant technical aspects of reactor and spent fuel safety in light of the accident.
The Task is Never Done
The meeting’s Chairman, Richard Meserve, Chairman of the International Nuclear Safety Group and President of the Carnegie Institution for Science, said, “In the nuclear business you can never say, ‘the task is done’.” It is an inherent responsibility to explore, examine, and assess the significance of nuclear safety and security vulnerabilities continuously.
The meeting gathered a wide range of expertise and perspectives to discuss the lessons now being learned from the accident. For instance, many Member States assessed the safety vulnerabilities of their nuclear power plants. These national assessments are supported by the IAEA’s complementary methodology for assessing nuclear power plants’ safety vulnerabilities, which was released in November 2011. The complementary methodology provides practical methods to assess whether structures, systems, components and operator actions are sufficiently resilient to be able to fulfill necessary safety functions when extreme events occur.
The results of the national assessments were discussed in detail at this experts meeting, which the IAEA organized as a part of its implementation of the Action Plan on Nuclear Safety. Approved in September 2011 by all IAEA Member States, the Action Plan provides a comprehensive programme and all the nuclear safety tools to systematically strengthen the global nuclear safety framework at the national, regional and international levels. The meeting served to meet one of the Action Plan’s objectives to facilitate a fully transparent assessment of the accident in cooperation with Japan.
In summarizing the Member States’ and the IAEA’s work to analyze the Fukushima accident and to take appropriate actions to respond, Meserve characterized these effort as “comprehensive, thoughtful and quite impressive.”
Presentations at the international experts meeting included a detailed update by Japan of the current understanding of the accident’s sequence. Meserve noted that much remains to be learned and continuing investigations will progressively allow for an even deeper analysis of the accident.
Together with the meeting’s co-chairs, 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, Meserve summarized the meeting’s conclusions, noting that the IAEA Member States’ regulators, industry, operators and technical support organizations, and other relevant organizations had made “good progress in improving safety and a large number of activities are in process.” Member States, both regulatory bodies and operators, are “taking aggressive actions to increase safety.” And the IAEA Action Plan is providing an appropriate framework for the development and sharing of essential lessons learned.
While the Member States’ analyses were independent and utilized different approaches to study different aspects of the accident, Meserve said that the set of conclusions has converged around similar recommended actions to be taken. “I take confidence from the fact that these similarities suggest that significant issues have not been overlooked.”
The Member States’ analyzed and shared several common safety improvement priorities, including, enhancing nuclear power plant protection against extreme events, earthquakes, tsunamis, flooding, and tornadoes and their consequences, such as total “station blackout”, loss of reactor and spent fuel pool cooling and loss of communications. Several recommendations were presented on enhancing emergency response and hydrogen explosion control, as well as providing for more robust instrumentation that can withstand accident conditions to ensure the continued monitoring of key safety parameters in the reactors and spent fuel pools. Experts recommended that more attention be paid to implementing stronger accident mitigation measures and improving emergency management capabilities.
Nuclear power plants are designed to handle “design basis” accidents as a part of their licensing process in accordance with established design criteria and conservative methodology. Experts also discussed the establishment of a much more robust capacity to deal with accident conditions that are more challenging to the design.
Several of the presentations proposed establishing an additional layer of protection to prevent a severe accident, regardless of the initiating event. This additional protection would prevent an accident’s progression to a situation that results in fuel damage and melting. Additional fixed and mobile equipment should be considered to provide the increased capacity to meet essential functions, such as delivering power and cooling water. This should result in “greatly strengthened defense in depth,” Meserve said.
Since many lessons from the accident are yet to be learned, participants felt that preparing a full report on all the important information presented at this experts meeting would be beneficial, and also suggested that an International Experts’ Meeting of similar scope could be convened in the future. Lessons derived from the meeting should inform the implementation of the Nuclear Safety Action Plan and should be evaluated for possible incorporation into IAEA safety standards.
Many countries are strengthening severe accident management and these efforts will benefit from continuing such interaction among international experts. The experts also proposed that further research be undertaken to better understand how accidents progress and to develop scenarios to expeditiously identify the relevant lessons from the accident.
“The Three Mile Island and Chernobyl accidents brought about an overall strengthening of the safety system, it is already apparent that the Fukushima accident will have a similar effect,” Meserve said.
Action to Strengthen Nuclear Safety
Under the Nuclear Safety Action Plan, IAEA Member States conduct assessments of the safety vulnerabilities of nuclear power plants in the light of lessons learned from the Fukushima accident. The framework for IAEA peer reviews is being strengthened. The effectiveness of national and international emergency preparedness and response arrangements, IAEA safety standards and the international legal framework is also being reviewed. National regulatory bodies, as well as the management systems, safety culture, human resources management and scientific and technical capacities in operating organizations are being regularly reviewed. The IAEA helps newcomers create an appropriate nuclear infrastructure based on IAEA Safety Standards. National capacity building programmes that sustain nuclear safety are being expanded. The IAEA is cooperating on monitoring, decontamination and remediation with Japan. The effectiveness, transparency and dissemination of communications during a nuclear emergency are being improved. Research and development is underway in areas highlighted by the accident, such as extreme natural hazards.
The International Nuclear Safety Group was convened in 1985 by the IAEA. The Group’s members are recognized nuclear safety experts who provide authoritative guidance, recommendations and opinions on current and emerging nuclear safety issues to the IAEA, the nuclear community and the public.