The Fukushima earthquake + tsunami and other recent external events that have challenged the design basis for commercial nuclear power plants
Peter Lobner,Vice President
Rolls-Royce, Instrumentation & Controls
Key tenets of commercial nuclear power plant (NPP) design include protection against the effects of severe natural phenomena, protection by multiple fission product barriers (defense-in-depth), and redundancy and/or diversity of the systems that perform safety functions (single failure criterion). In this discussion, we will review the 2011 Fukushima accident timeline and identify the points at which various aspects of the original design basis were exceeded as the plant moved into a relatively uncharted region beyond the design basis. In this region, plant behavior was dictated largely by physical processes and there were few resources available to the plant operators to mitigate the sequence of events. Through the extraordinary ad hoc efforts of the emergency response team, the Fukushima plants eventually were stabilized to the point that Tokyo Electric Power Company declared the plants to be in “cold shutdown” in December 2011. Estimates by the Japanese government indicate that completion of site decommissioning will take 30-40 years.
Also in 2011, other severe external events provided additional insights into the adequacy of the reactor design basis for protection against tornados, river flooding, and earthquakes. These events, which affected the Browns Ferry, Fort Calhoun and North Anna NPPs, will be briefly reviewed.
The U.S. Nuclear Regulatory Commission, with input from the U.S. nuclear industry and Nuclear Energy Institute (NEI), is working to define the regulatory implications of Fukushima for existing and new NPPs in the U.S. The current status of these NRC and industry efforts will be summarized.
The international repercussions of Fukushima have been mixed, with a few nations backing away from nuclear power, notably Italy and Germany, while others remain committed to deployment of new NPPs. The current status of international commercial nuclear power programs will be summarized.
The following is a link to the PowerPoint presentation (ppt file extension).