Session W20: Invited Session: Nuclear Power, One Year After Fukushima

The Accident at TEPCO's Fukushima-Daiichi Nuclear Power Plant: Technical Description of What Happened and Lessons Learned for the Future

Tsunami that followed M9.0 earthquake on March 11$^{th}$ left the Fukushima-Daiichi Nuclear Power Plants without power and heat sink. While water makeup continued by AC-independent systems to keep the fuel core covered by coolant, operating team tried to depressurize and enable low pressure injection to the reactor to avoid overheating but was not successful enough primarily due to limited available resources. This resulted in core melt, hydrogen explosion and release of radioactivity to the environment. Key lessons learned are; 1) safety regulation and safety culture, 2) workable/executable severe accident management procedure, 3) crisis management and 4) design. Implications on security include revealed vulnerability and the nexus of safety and security. Given the scale of damage to the environmental, attention must be paid to defense against it and to societal safety goal of nuclear power by considering offsite remedial costs, compensation to damage, energy replacement cost etc. A sort of root cause analysis first by asking ``Why nuclear community failed to prevent this accident?'' was initiated by the University of Tokyo.   

The U.S. nuclear industry following the Fukushima event

The nuclear industry is executing a coordinated, comprehensive and safety focused strategic plan in response to the accident in Japan. This beyond design basis external hazard driven event resulted in loss of core cooling due to a loss of offsite power as a result of the significant earthquake which was followed by a loss of on-site power due to the tsunami. Site response actions were impacted due to difficulty accessing the site. The current US fleet of operating reactors has over the last decades implemented numerous reviews assessing external hazards with post 911 actions being the most current. The industry took immediate actions following the March accident to verify existing capabilities to address events driven from external hazards and is now implementing a ``Way Forward'' plan that has as a priority the continued safe operation of the existing US fleet while examining both the technical and organizational root causes of the Fukushima Dai-ichi accident. Industry focus is to provide additional defense in depth through a ``Flex'' approach that adds the most significant safety benefit in the most efficient time frame. From a topical perspective, the industry is in agreement with the tier 1 recommendations from the NRC near term task force report. Southern Nuclear Operating Company operates 6 reactors and is building Vogtle 3\&4 which is expected to be granted a COL in the near term. This generation III+ reactor design has passive safety features that would have mitigated an event similar to the Fukushima accident.   

Lessons from Fukushima for Improving the Safety of Nuclear Reactors

The March 2011 accident at the Fukushima Daiichi nuclear power plant has revealed serious vulnerabilities in the design, operation and regulation of nuclear power plants. While some aspects of the accident were plant- and site-specific, others have implications that are broadly applicable to the current generation of nuclear plants in operation around the world. Although many of the details of the accident progression and public health consequences are still unclear, there are a number of lessons that can already be drawn. The accident demonstrated the need at nuclear plants for robust, highly reliable backup power sources capable of functioning for many days in the event of a complete loss of primary off-site and on-site electrical power. It highlighted the importance of detailed planning for severe accident management that realistically evaluates the capabilities of personnel to carry out mitigation operations under extremely hazardous conditions. It showed how emergency plans rooted in the assumption that only one reactor at a multi-unit site would be likely to experience a crisis fail miserably in the event of an accident affecting multiple reactor units simultaneously. It revealed that alternate water injection following a severe accident could be needed for weeks or months, generating large volumes of contaminated water that must be contained. And it reinforced the grim lesson of Chernobyl: that a nuclear reactor accident could lead to widespread radioactive contamination with profound implications for public health, the economy and the environment. While many nations have re-examined their policies regarding nuclear power safety in the months following the accident, it remains to be seen to what extent the world will take the lessons of Fukushima seriously and make meaningful changes in time to avert another, and potentially even worse, nuclear catastrophe.   

Nuclear Power in China

In response to the Fukushima accident, China is strengthening its nuclear safety at reactors in operation, under construction and in preparation, including efforts to improve nuclear safety regulations and guidelines based on lessons learned from the accident. Although China is one of the major contributors in the global nuclear expansion, China's nuclear power industry is relatively young. Its nuclear safety regulators are less experienced compared to those in other major nuclear power countries. To realize China's resolute commitment to rapid growth of safe nuclear energy, detailed analyses of its nuclear safety regulatory system are required. This talk explains China's nuclear energy program and policy at first. It also explores China's governmental activities and future nuclear development after Fukushima accidents. At last, an overview of China's nuclear safety regulations and practices are provided. Issues and challenges are also identified for police makers, regulators, and industry professionals.   

Nuclear Power in India

India has ambitious plans for expanding nuclear power over the next few decades. A major accident in a densely populated country like India can be catastrophic and thus of concern. There are both technical and organizational requirements for safety of nuclear facilities. This talk will describe some of the organizational factors that safety theorists have identified and examine, from the publicly available information about incidents and failures at India's nuclear facilities to see if these requirements are met. It will also describe some of the reactions to the Fukushima accident from officials associated with nuclear energy in India.