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Nuclear Safety: A Maturing Discipline

Berlin Germany

In the first controlled nuclear chain reaction in history - Enrico Fermi's 1942 Chicago Pile experiment - the concept of 'nuclear safety' consisted of three cadmium rods. The first was operated by hand. The second, driven by a motor, was to be triggered automatically when core reactivity reached a certain level. The third rod, held by a rope and pulley, was dependent on the reflexes of a man with an axe, standing by to chop the rope and shut down the reaction before things got out of control.

It is gratifying to note, 61 years later, that our concepts of 'Defence in Depth' - and nuclear safety overall - have evolved considerably. But it is also interesting to observe that the basic elements of the equation remain essentially the same: automatic safety features, emergency back-ups, and the human interface, all coordinated in an effort to manage and minimize the risks associated with harnessing nuclear energy. Today I will review a number of the key lessons we have learned from the successes and failures of the past six decades.

Importance of a Strong, Independent Regulator

In the early years of nuclear science, the cadre of scientific expertise was relatively small. As a result, the R&D efforts associated with nuclear power and nuclear weapons were often closely linked, and therefore highly secretive and under tight governmental control. In many cases, the national agencies set up to promote the expansion of nuclear power were also made responsible for regulating its safety - a dual responsibility that led to clear conflicts of interest, including cover-ups of important safety issues.

This has clearly changed over time; it is now widely recognized that a nuclear safety regulator must be granted the proper legislative authority and have sufficient funding to carry out its mandate. To be effective, the regulator must be firm, fair and transparent - with regulatory actions readily defensible and credible when exposed to public scrutiny. The regulator must also be independent, and be perceived as such. The credibility of regulatory actions has at times been diminished, in the public view, when the regulatory body and the promotional agency - or in some cases even the utility operator - have come under the authority of the same governmental ministry.

These criteria for establishing a strong, independent regulator have been incorporated into the IAEA's safety standards. However, some of these criteria have yet to be followed in the regulatory structures of many countries.

Three Mile Island and Chernobyl: Watershed Events

The two 'watershed' events in the history of nuclear power - the 1979 accident at Three Mile Island, and the Chernobyl disaster seven years later - have left indelible imprints that still dominate public discussions of nuclear power safety. But it is important to emphasize that the lessons of TMI and Chernobyl also had an enduring positive effect on the subsequent safety performance of the nuclear industry. I would like to focus briefly on three of those lessons.

First, while the concept of 'Defence in Depth' was present in the design of nuclear power plants since their inception, it was TMI that first made clear the need for redundancy and diversity in all aspects of safety related equipment: electrical supply, sources of coolant, and injection pathways. Even more important, both TMI and Chernobyl illustrated dramatically the need to ensure that operators could be relied on to mitigate the consequences of an accident, rather than compounding it - and in that regard, stressed the need for our analysis of Defence in Depth to include consideration of the human factor, through design, training, procedures, and what has become our overall focus on fostering a 'safety culture'. The accidents also showed that Defence in Depth should encompass emergency preparedness, so that effective response to an accident would, inter alia, provide clear messages to the public and efficient coordination of any actions needed to preserve public safety.

Second, the Chernobyl accident in particular demonstrated the need for globalized co-ordination on nuclear safety issues. It drove home the truism that "an accident anywhere is an accident everywhere." This is because of the plume of radioactive gases and particles that severely contaminated areas in Ukraine and Belarus but also were detectable in many parts of the world. This underscored: the importance of global information networks for sharing operational expertise; the benefits of international peer reviews to identify 'best practices', helping all countries to raise their operational safety standards; and the candid dissemination of lessons learned when problems are discovered. The IAEA's three-faceted approach to improving international nuclear safety - urging the adoption of binding international safety conventions, promoting universal adherence to safety standards of the highest quality, and conducting review missions across the full range of safety topics - reflects our commitment to globalized nuclear safety norms, practices and co-ordination.

The IAEA nuclear safety role complements that of other international organizations. Our safety review and appraisal services assist Member States in the application of IAEA safety standards, and provide useful feedback on their effectiveness to governments and regulators. These services originated predominantly in the field of nuclear installation safety, but now extend to cover regulatory effectiveness as well as radiation, radioactive waste and transport safety. The World Association of Nuclear Operators (WANO) supports and complements this focus on the safety of nuclear installations, by providing confidential peer reviews to the operators, and helping to ensure that lessons learned on technical and safety matters are communicated to them. And the World Nuclear Association (WNA) serves as the focal point and spokesperson for its members, providing coherent representation and insight regarding industry views on safety issues to safety standard setting bodies such as the IAEA and the International Commission on Radiological Protection..

Third, both the TMI and Chernobyl accidents highlighted the need for improved understanding and management of the safety risks of nuclear activities. This lesson took some time to apply effectively. While probabilistic risk assessments - systematic assessments of a nuclear facility's vulnerability to severe accidents - began to gain increasing sophistication in analysis, it was only in the early-to-mid-1990s that regulators and operators began to find practical ways of applying these analyses..

Effective risk management takes into account the results of probabilistic risk assessments, combines these considerations with other factors - such as public concerns or legislative mandates - and creates 'bottom-line' performance criteria that will acceptably limit the risks. For regulatory bodies, risk management allows the sensible prioritization of inspection and enforcement practices, to put the greatest emphasis on those areas of greatest risk. For operators, it enables correspondingly smarter investments, broadens the awareness of which components, systems and plant operations are most critical in avoiding accidents, and enables far more effective scheduling of component maintenance and plant outages in a way that maximizes plant safety, reliability and online availability. For all parties, the use of risk information also provides a sensible and defensible basis for communication - not only within the nuclear community, but also with the public - on issues related to nuclear safety.

It has long been apparent that, in order for nuclear power to have a future, it must be both economically viable and unequivocally safe. Far from being a paradox, the safety performance recorded by WANO and other bodies in recent years has shown that high standards of safety go hand in hand with improved economic performance.

Radiation Safety Infrastructure: Prerequisite to Technology Transfer

As you are all aware, the scope of the IAEA's safety activities extends beyond the nuclear power arena. In many countries, the IAEA has been involved in the beginning stages of transferring nuclear technology to address other high priority humanitarian issues - such as improved health care, increased agricultural productivity and more effective management of water resources. The technologies involved in these cases, while less complex than nuclear energy production, still require a basic safety infrastructure to be in place. Many of the same lessons, such as the need for transparency, independent regulatory oversight, and an approach to Defence in Depth that addresses the potential for human error, are just as applicable when seeking to ensure safety in the use of radioactive sources. Early experience in the transfer of nuclear technology showed that many countries required substantial support in the development of such an infrastructure, in order to avoid severe, even fatal overexposures to radiation.

In 1994, the IAEA launched an ambitious technical co-operation effort, using the so-called 'Model Project on Upgrading Radiation Protection Infrastructure', to help developing countries establish national programmes compatible with the Agency's Basic Safety Standards for radiation protection and source safety. More than 80 countries have become involved with applying this Model Project approach and, while much work remains to be done, we have seen substantial benefits realized in the effectiveness of the radiation safety infrastructures established.

Our consideration should also include the merits of multinational approaches to the management and disposal of spent fuel and radioactive waste. Not all countries have the appropriate conditions for geologic disposal - and, for many countries with small nuclear programmes for electricity generation or for research, the financial and human resource investments required for research, construction and operation of a geologic disposal facility are daunting. Considerable economic, safety, security and non-proliferation advantages may therefore accrue from international co-operation on the construction and operation of international waste repositories. In my view, the merits and feasibility of these and other approaches to the design and management of the nuclear fuel cycle should be given in-depth consideration. The convening of an Agency group of experts could be a useful first step.

Nuclear Security: A Lesson in Balance

The September 2001 terrorist attacks in the United States provided the impetus for re-evaluation of security in every industrial sector, including nuclear power. The potential threats of nuclear and radiological terrorism have taken on new urgency. Around the world, nuclear plants have strengthened security forces, added barriers, and taken other protective measures to address new perceptions of security risks. The IAEA has greatly expanded the scope and volume of its nuclear security activities. Since September 2001, working in Europe, Asia, Latin America, North America and Africa, we have conducted over 40 advisory and evaluation missions, and convened more than 60 training courses, workshops and seminars - all focused on improving countries' capabilities for protecting against nuclear and radiological terrorism.

It is important to understand how safety and security aspects come together in the identification and protection of vulnerabilities in nuclear installations. The IAEA has increasingly been asked to provide guidance on how to reconcile the need for transparency, in matters of nuclear and radiation safety, with the need for confidentiality, from a security perspective. Effective risk management will involve striking a balance that protects the security of sensitive information while ensuring that safety concerns continue to be corrected in a transparent manner, and that lessons learned, relating to both safety and security, are shared for the benefit of the entire nuclear community.


Looking to the future, a number of nuclear safety challenges remain. A key focus will be to 'manage the tension' to which I have just referred, to ensure that both safety and security goals are met for nuclear installations and nuclear materials - as well as to ensure the safety and security of radioactive sources worldwide. A second challenge involves 'the management of nuclear knowledge': improving the 'succession planning' for the nuclear industry - working to develop a younger generation of scientists and engineers with the proper education and skills to replace the aging nuclear workforce - a challenge on which John Ritch and the WNA have recently moved forward with the launch of the World Nuclear University.

Another challenge related to the management of nuclear knowledge involves recurring events. Despite continued efforts by the entire nuclear community to share lessons learned from events that have occurred in nuclear facilities throughout the world, incidents with similar root causes continue to recur - often with safety culture implications. This has been seen in IAEA Member States with both robust and evolving regulatory infrastructures. A focused commitment is needed to ensure that lessons learned in one country are effectively and thoroughly communicated to all countries, and that these lessons are incorporated into the operational and regulatory practices of all relevant nuclear facilities.

The final challenge lies in our continuing efforts to ensure that nuclear facilities worldwide are operated according to the highest levels of safety. In some cases, for existing facilities with older design features, this still will require upgrades or compensatory measures. And for all facilities and operators, this challenge remains one of enduring vigilance, managing the risks associated with nuclear power in a manner that will enable its continuing contribution to the benefit of humankind.


Last update: 26 July 2017