This article provides an insight into critical elements, challenges, and next steps of the ASME’s Presidential Task Force, which has been formed to examine unforeseen nuclear plant events and their implications. Within its broad charter, the ASME Task Force chose to build on the growing body of United States and international technical assessments of different events, and to examine the Fukushima Daiichi accident in the context of the broader lessons learned from a half-century of nuclear operations. This initiative could be perceived as just another layer of requirements limiting the economic viability of nuclear power. On the contrary, the intention is to support the overall viability of safe nuclear generation. The ASME Task Force is convinced that a new nuclear safety construct can be developed that addresses the safety issues from the Fukushima lessons learned with reasonable and well-defined provisions. The ASME Task Force report recommends a set of next actions in this regard, particularly using the experience, stature, and capabilities of ASME in convening workshops, to bring together worldwide stakeholders including industry, regulators, professional societies, government agencies, and industry organizations worldwide.
The March 2011 Great East Japan Earthquake and Tsunami caused great loss of life and property in the nation of Japan, and devastation to the environment. The extraordinary forces and flooding unleashed on the east coastal area also led to severe nuclear plant damage and radiological releases at the Fukushima Dai-ichi station. The global impact of the accident at Fukushima prompted the ASME President, Victoria Rockwell, to commission a Presidential Task Force to examine those nuclear plant events and their implications. The unprecedented accident at Fukushima exposed new information on nuclear power plant vulnerabilities to extreme external events and exposed the need for pertinent improvements. The multi-unit nuclear plant accident at Fukushima continues to have serious impacts on sociopolitical, economic, and energy-related issues in Japan and worldwide. Within its broad charter, the ASME Task Force chose to build on the growing body of U.S. and international technical assessments of these events, and to examine the Fukushima Dai-ichi accident in the context of the broader lessons learned from a half-century of nuclear operations. From the combination of assessments and reviews of the critical elements involved in the accident scenarios, the ASME Task Force proposes a cohesive framework for continued safe operation of nuclear plants.
Fukushima Dai-Ichi—In Context
From the vast body of observations, analyses, and reporting of the events at Fukushima, several points stand out as the most salient factors in assessing its long-term implications:
The Fukushima Dai-ichi units are the first nuclear reactors in the world in the fifty-plus years of nuclear plant operation to sustain core degradation due to catastrophic external events, the first to involve simultaneous multiple unit failures, and the first light water reactors to release large amounts of radioactivity to the environment.
The reasons why four of the Fukushima Dai-ichi units were severely damaged and three suffered core meltdowns have been identified and are correctible. The lessons learned from the ten other nuclear plants in the affected areas that were impacted to varying degrees are also being applied. Principal among those were the now recognized inadequacies in plant design basis for tsunamis, flooding, and accident management.
The Fukushima Dai-ichi accident reveals no fatal flaw in nuclear technology, yet multiple important safety improvements are being addressed by the global nuclear fleet from the new lessons learned.
▪ Extensive evaluations of the Fukushima Dai-ichi accident confirm the absence of prompt fatalities from radiological effects and the continuing expectation of no delayed radiological public health effects. The relatively low potential for radiological health consequences from the Fuku- shima accident is consistent with actual experience with radiation effects.
Protection of public health and safety from radiological releases has been and continues to be the primary focus of reactor safety. However, past and present experience shows that the major consequences of severe accidents at nuclear power plants have been sociopolitical and economic disruptions inflicting enormous cost to society. As of the report issue date (June 14, 2012), 15 months after the March 2011 disaster, about 90,000 residents in that region are still not able to return to their homes, pending a more complete radiological cleanup. As of May 5, 2012, all of the 54 nuclear power plants in Japan had been shut down, though as of this writing, the Japanese government had given approval for the restart of several reactors, but the nation continues to struggle with an energy supply shortfall. Estimates of the overall economic consequences of the Fukushima Dai-ichi accident are on the order of half a trillion U.S. dollars.
After a detailed review, such unacceptable consequences—even though caused by an extreme and, in some respects, unprecedented natural disaster—appear to have been preventable and are wholly inconsistent with an economically viable and socially acceptable use of nuclear energy.
The primary nuclear power safety goal is and will continue to be protection of public health and safety. However, the Fukushima Dai-ichi accident revealed the need for additional steps to further reduce the potential for socio-political and economic consequences resulting from radioactivity releases. On that basis, the ASME Task Force has proposed a new nuclear safety construct to effect such improvement. The nuclear safety construct is to be the set of planned, coordinated, and implemented systems ensuring that nuclear plants are designed, constructed, operated, and managed to prevent extensive societal disruption caused by radioactive releases from accidents, using an all-risk approach.
The new nuclear safety construct is founded on the existing nuclear safety construct. The new construct will expand on the evolving safety frameworks, reaching beyond adequate protection of public health and safety to prevent socio-political and economic consequences from a severe nuclear accident.
It extends the design basis to consider all risks, and includes rare yet credible events. The ASME Task Force proposes that the new safety construct be based on an allrisk approach, addressing a broad range of challenges to nuclear power plant safety, including internal and external hazards, during all modes of plant operation, evaluated in a risk-informed manner. Cliff-edge events—those for which a small incremental increase in severity can yield a disproportionate increase in consequences—should be discovered and mitigation approaches implemented. The objective in addressing rare events with potentially extreme consequences is to take reasonable and practical measures to deal with credible events that until now have not been fully considered, while realizing that the overall risk will not be zero.
It extends beyond regulations. It is the ASME Task Force view that accountability for protection of people and property must extend beyond the regulatory requirements to plant designers, manufacturers, owners, and operators.
It must be embraced globally. The ASME Task Force recognizes the inherent difficulty in applying any standard across different corporate and regulatory regimes and cultures, but the reality remains—as evidenced starkly by the Fukushima Dai-ichi accident—that the viability of nuclear energy is a global proposition, and that safety principles apply to all plants.
The ambitious objective set by the ASME Task Force—to develop, adopt, and support the implementation of a new nuclear safety construct—presents daunting challenges. Principal among these is building global consensus on its principles, details, and implementation.
Among the many owners, operators, and regulators of nuclear plants around the world there are differences in culture, regulatory structure, technical sophistication, government involvement, economy, environment, politics, and the like. The ASME Task Force recognizes these differences and their implications on the practical work of developing a consensus on the level and nature of extreme events against which the plant, people, and property must be protected. Nevertheless, it will be necessary to work together, to find the common denominators, and to achieve global alignment on the fundamentals of nuclear safety.
This initiative could be perceived as just another layer of requirements limiting the economic viability of nuclear power. On the contrary, the intention is to support the overall viability of safe nuclear generation. The ASME Task Force is convinced that a new nuclear safety construct can be developed that addresses the safety issues from the Fukushima lessons learned with reasonable and well-defined provisions. Unless consequences such as those experienced in Japan can be avoided, even when confronted with extreme natural events, nuclear power will not be socially acceptable and economically viable over the long term. Building public trust is an essential component in prevention of adverse sociopolitical and economic consequences from nuclear plant accidents.
From this starting point begins the real work of building consensus, developing the new nuclear safety construct in full detail, determining the roles of the various stakeholders, and then adopting and implementing it globally. The ASME Task Force report recommends a set of next actions in this regard, particularly using the experience, stature, and capabilities of ASME in convening workshops, to bring together worldwide stakeholders including industry, regulators, professional societies, government agencies, and industry organizations worldwide.
Editor’s note: This article is adapted from a selection of the ASME Presidential Task Force’s report. The full text of the report, “Forging a New Nuclear Safety Construct,” is available online athttp://www.asme.org/kb/standards/publications/forging-a-new-nuclear-safety-construct.