Science is a discipline that explores the outer reaches of possibility to solve problems. One of the most intriguing challenges that scientists and engineers of the nuclear industry face is preparing for unexpected events – both natural and manmade – that have never occurred before.
Ever since the U.S. began harnessing the power of nuclear energy to produce electricity, reactors have been designed with layer upon layer of protection to keep people who work and live nearby healthy and safe. The tsunami that struck Japan’s Fukushima Dai-ichi nuclear site on March 11, 2010 highlights the scientific challenge of imagining extremely unlikely events and then developing effective measures to safely mitigate the negative impact of those events.
The damage caused by flooding in the aftermath of the tsunami has brought some of the world’s best scientific minds together to evaluate how the nuclear industry can be better prepared for unprecedented events. In late January, the Nuclear Regulatory Commission (NRC) hosted a workshop during which leading experts in the nuclear industry shared ideas and informed participants on state-of-the-practice strategies for extreme flood assessments.
During the workshop, the full spectrum of flood-related issues, including dam and levee safety, extreme storm precipitation, hurricane and storm surges and tsunamis, were put under a microscope to determine the best models for assessing and addressing vulnerabilities at nuclear plants. The program gave participants the opportunity to review flood hazard studies that have already been performed post-Fukushima and discuss which models will most effectively anticipate extreme flood protection needs in the future.
The workshop is one of multiple actions the NRC has been taking since the days immediately following the Fukushima disaster to capture lessons learned from the event. The NRC’s goal is to develop a clear and practical framework to assess current safety and emergency preparedness strategies and make recommendations for additions or modifications to bolster existing safety systems.
As part of its focus on flood protection, the NRC established guidance for reevaluating flood hazards at each site and comparing the reevaluated hazard to the current design basis at the site for each flood protection mechanism.
Flood protection features at nuclear power plants are diverse because of differences in topography, location of the plant relative to water sources, plant design and other factors. As a result, NRC’s guidelines are designed to accommodate the unique characteristics of individual plants. At the same time, the guidelines ensure that the information gathered provides sufficient technical basis to determine if additional flood protection measures are necessary.
While all nuclear plants in the U.S. are performing a re-evaluation of flooding hazards during the next three years, Oconee Nuclear Station (ONS), located in Oconee County, S.C., is one of the lead sites with a requirement to complete the re-evaluation by March 2013.
“Oconee has updated our flooding analysis based on the most advanced models to better anticipate and prepare for flooding, no matter how unlikely flooding events might occur,” said ONS Site Vice President Preston Gillespie. “Part of our investment in Oconee includes raising the height of barriers around critical equipment and strengthening walls to protect against flooding, high winds, earthquakes and other natural forces.
“As we celebrate our 40th year of operating safely, we look forward to continuing to work with our industry partners to identify opportunities to augment our safety systems and develop long-term solutions that incorporate lessons learned from Fukushima,” he added.