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Natural Hazards Are Part of the Planning

Scott Burnell
Public Affairs Officer

 

Up to now the 2014 Atlantic hurricane season has been pretty calm, but the NRC always keeps an eye out for the strong weather-related events and other natural events the world can generate. We make sure both U.S. nuclear power plants and the agency are prepared for high winds, storm surge and a whole lot more.

Most recently, the seven reactors affected by 2012’s Superstorm Sandy remained safe. Other plants have safely withstood powerful storms, including Waterford 3 in Louisiana handling the effects of 2005’s Katrina and Turkey Point in Florida safely taking a direct hit from 1992’s Andrew.

Sandy may have left a mess in New York, but the nuclear reactors in its wake remained safe. Photo courtesy of FEMA

Sandy left a mess in New York, but the nuclear reactors in its wake remained safe. Photo courtesy of FEMA

Flooding can happen with or without storms, and U.S. plants are designed to and safely ride out significant events, such as when Fort Calhoun in Nebraska dealt with an overflowing Missouri River in 2011. Also in that year, Vermont Yankee remained safe as the Connecticut River valley suffered severe short-term floods from Hurricane Irene’s remnants.

Japan’s Fukushima Dai-ichi nuclear accident in March 2012 showed the world what flooding (in this case from a tsunami) can do to a reactor. The NRC’s learned several flooding-related lessons. from the accident. As a result of NRC direction, U.S. plants are using the latest software and technical know-how to re-analyze all flooding sources. This will help the NRC determine if the plants need to consider higher flooding water levels when establishing plans to stay safe. This effort has also examined existing flood protection and all plants have taken steps to confirm they can implement reliable flood safety plans. In the meantime, several plants have also chosen to enhance their flood protection.

An earthquake caused the tsunami that devastated Fukushima, and again U.S. plants are designed to stay safe in the face of quakes that affect their area. Virginia’s North Anna plant was hit by an August 2011 quake centered a short distance away. The earthquake was strong enough to be felt across the East Coast; it shook North Anna with a little more force than what the plant was originally designed to withstand. North Anna remained safe – multiple inspections showed the plant’s systems were undamaged. This was unsurprising, since plant systems are designed to withstand a combination of events that can exceed the forces generated by an earthquake alone.

As with flooding, the NRC has learned from Fukushima’s quake and other recent earthquakes, and we’re having every U.S. plant reanalyze earthquake hazards to see where enhancements might be needed. All the plants east of the Rockies have taken the first step in that process, and the other plants will do the same next March.

U.S. reactors are also designed for (and have safely survived) hazards such as tornadoes, droughts and other severe weather events. Even with all this preparation, Fukushima reminds us to prepare for the unexpected. The NRC’s approach here involves every U.S. reactor having additional portable systems to restore and maintain safety functions.

All of this work helps ensure the public stays safe when natural disasters strike that may impact U.S. nuclear power plants.

Fukushima Daiichi Now: Images and Perspectives

NRC officials tour one of the damaged units at the Fukushima Daiichi plant during their trip in February.
NRC officials tour one of the damaged units at the Fukushima Daiichi plant during their trip in February.
Roger Hannah
Senior Public Affairs Officer
Region II
 

In February, an NRC delegation, mostly comprised of senior managers responsible for reactor oversight, travelled to Japan to see, hear about and learn from the accident there in March 2011.

I was there to record the images and sounds of the trip – from the meetings to the tours of facilities, including the stricken Fukushima Daiichi plant, and the surrounding countryside. In interviews and conversations, I heard varied perspectives, but my focus was almost completely on people:

  • The people whose homes and businesses and schools now sit abandoned near the plant – some knowing they may never go home again.
  • The people who worked at the plant during and after the accident trying to keep the situation from being worse.
  • The people who now work at the site donning protective clothing each day as they slowly tackle the mammoth cleanup.
  • The people across Japan who continue to struggle with their view of nuclear power.

I wish we had been able to spend more time in the evacuated areas near the plant, but even the hours we were there carved indelible images in my memory. It’s interesting how seeing areas without people made me think about the missing people even more.

When it comes to nuclear safety, the most important people are those working inside or living closest to the plants. There is no stronger evidence than the images we captured during the trip.

It was difficult to distill all we saw and heard into the short video we posted on the NRC YouTube channel, but I hope we were able to show the essence of the trip…and for me, it was all about people.

 

Fukushima Lessons: Updating Earthquake Hazards at U.S. Nuclear Plants

Scott Burnell
Public Affairs Officer
 

The NRC is examining new earthquake-related information from U.S. nuclear power plants, and we’re making that information available over the next week or so. We’d like to summarize how we got here and what the next steps are.

seismicgraphicNuclear power plant designs set a basic standard for reactors to completely and safely shut down after an earthquake, based on site-specific information. Plant construction methods and other design factors add to a reactor’s capacity to safely withstand stronger motions than what the basic design describes.

The end of March marked an important milestone for our post-Fukushima activities. We received 60 reports from central and eastern U.S. nuclear power facilities updating the seismic hazard at their individual reactors. The NRC staff is making these reports available through its normal process. The NRC will post each plant’s report on the agency website’s Japan Lessons-Learned Activities page.

We will require the same updates of the three western power plants (Palo Verde in Arizona, Columbia Generating Station in Washington, and Diablo Canyon in California), but delayed by one year because of the more complex geology in that region of the country. Each western plant is individually looking at the seismic sources and local ground motion characteristics that could affect it. This Senior Seismic Hazard Analysis Committee process will inform the overall seismic hazard reassessment that the western plants are completing.

Our staff will spend the next month going over the submissions carefully, checking for errors, before confirming which plants will be required to do more extensive analysis of their ability to respond safely to a significant earthquake event.

These reports mark the first step in a comprehensive process to keep safety at U.S. plants up-to-date with the latest understanding from the earth sciences on the processes that create earthquakes in the U.S.  In 2012, the Department of Energy, Electric Power Research Institute and the NRC joined forces to update the “seismic source model” for the central and eastern U.S. This was based on a new understanding of what creates earthquakes on the North American tectonic plate, with a focus on the New Madrid fault zone near St. Louis, the Charleston fault zone near Charleston, S.C., and other updated information.

The data on seismic sources will be used in conjunction with a ground motion model for the central and eastern U.S. as well as data from individual plants on the localized geology, topography, soil cover, and other data to create a picture of the “ground motion response spectra” for each plant. This new ground motion response spectrum at each plant will be compared with that developed in the past to see if the new data suggests the plant could see higher ground motions than previously thought. If that is the case, the plant will be considered to have “screened in” to further detailed seismic hazard analysis.

Those plants that “screen in” will be required to do a seismic “probabilistic risk assessment” or a seismic “margin analysis” to evaluate in detail how the existing plant structures and systems would respond to the shaking from the range of earthquakes that could affect the plant based on our current understanding of seismic sources. This assessment is extensive, involving experts from a variety of fields, and will require at least 3 years to complete. Once these assessments are complete, the NRC will decide if significant upgrades to plant equipment, systems, and structures are required.

In the meantime, to ensure that the plant is safe, the NRC requires that by the end 2014, plants have reported the interim actions they will take to ensure the safety of the plants before the assessment is complete. Such measures could include re-enforcing existing safety-significant equipment or adding equipment.

It’s important to remember that significant earthquakes at central and eastern U.S. plants are unlikely. But it is our job to ensure that these plants are ready for all that nature might throw at them. And it is our job to keep up with the changes in the science to ensure that plants are as safe as they can be.

Addressing the Unpredictable Through Mitigation Strategies

Lauren Gibson
Project Manager
Japan Lessons-Learned Directorate
 

The Fukushima accident reminded us how important prior planning is when it comes to safely handling extreme events at a nuclear reactor. We continue to conclude U.S. plants can survive many scenarios, such as loss of offsite power or flooding. After Fukushima, however, we’re requiring plants to have strategies for dealing with the long-term loss of normal safety systems.  Instead of figuring out which events might happen, we’re focusing on significantly improving the plants’ flexibility and diversity in responding to extreme natural phenomena (such as severe flooding, earthquakes, extreme temperatures, etc.).

mitigation_strategies_infographic_r4The plants’ strategies must protect or restore key safety functions indefinitely in the case of an accident. The strategies focus on keeping the core cool, preserving the containment’s barrier that prevents or controls radiation releases, and cooling the spent fuel pool. Plants with more than one reactor must be able to do this for every reactor on site at the same time.

Ideally, plants would have everything for their strategies on site. The strategies must protect the plant indefinitely, however, so plants may need to bring in additional equipment or resources.  The order reflects this by having three phases with different requirements.

The first phase begins with the accident or event.  At this point, the plants will use installed equipment, such as steam-driven pumps or battery-powered systems, to protect or restore safety functions. The plants must be able to shift to the second phase before the installed equipment is exhausted.

The strategies’ second phase uses portable equipment that’s stored onsite, such as additional pumps or generators. This equipment is stored near the reactors and reasonably protected from severe weather or earthquakes. The phase two resources are brought to the reactors and connected to maintain the safety functions. During this phase, plants would also be able to transfer fuel from onsite tanks to the places were it’s needed to run generators and other equipment. Plants have to ensure the third phase can take over before the portable equipment runs out of supplies.

The final phase starts when outside help arrives. The nuclear energy industry is setting up two response centers to provide additional equipment and other resources to any U.S. reactor within 24 hours. One center is in Memphis, Tenn., and the other is in Phoenix, Ariz.

The plants have all submitted a plan for what they intend to do and use in each of these phases. The plans must also explain how the plants will have everything in place by the end of 2016.  We’ve been reviewing those plans and we’re at the point of issuing interim staff evaluations, which let the licensee know whether we think they are on the right track. The NRC will inspect the plants throughout this process to ensure the strategies will get the job done. Our website’s Japan Lessons Learned section has more information about the mitigation strategy requirements and related guidance.

Note: The graphic is now available on our Flickr site.

An NRC Official Writes About His First-Hand View of the Japan Nuclear Disaster

Eric Leeds
Director, Office of Nuclear Reactor Regulation
 

Last month, I traveled to Japan with a group of senior NRC executives, including all four Regional Administrators. We spent a busy week meeting with representatives from various Japanese organizations involved in nuclear activities, as well as touring the Kashiwazaki Kariwa, Fukushima Dai-ni and Fukushima Dai-ichi nuclear power plants.

At the end of almost every day, we took time to reflect, to discuss what we learned, and to record our thoughts. I wanted to offer a few personal insights from what I found to be a profound experience.

On the bus ride to the Fukushima Dai-ichi Nuclear Power Plant, the site of the accident in 2011, we passed through the town of Tomioka, about 7 to 10 km south of the site. Before the accident, Tomioka had been a vibrant seaside village of approximately 16,000 residents. It was a resort town, with its own train stop, beachfront, restaurants and hotels.

test11The town is now empty, uninhabitable because of radiological contamination (about 1 microsievert an hour). There are no inhabitants, no electricity, no running water. The damage caused by the earthquake and tsunami remains. Those who had lived in the town are now allowed to enter to visit their homes, but they can’t stay overnight. The authorities are decontaminating the town and plan to have it inhabitable in about three years. Thinking about the people who, for all this time, have lost their homes, lost their jobs, and lost their community leaves me feeling sick to my stomach. For me, a career safety regulator, the feeling is very personal.

When we reached the site, we boarded a different bus, a bus prepared for a contaminated site, with plastic herculite covering the seats and more plastic and duct tape covering the floor. We donned a full set of anti-contamination clothing, shoe covers, and respirators. There are about 250 cars, trucks, and buses on site, ferrying a site workforce of about 4,000 workers. As we passed workers at the site and in other vehicles, it struck me that everyone was wearing full anti-Cs, respirators, and helmets. It left me with an eerie feeling, as if I were in a science fiction movie.

We toured the site, often leaving the bus to see specific site areas. While a great deal of work has already been accomplished, much of the damage from the earthquake and tsunami remains, if only pushed to the side. Broken buildings, twisted metal, crushed concrete and smashed vehicles still litter the site. TEPCO is currently moving the spent fuel from the Unit 4 spent fuel pool to the common pool for the site, and we toured both pools. Since we could not get into the containments of the damaged reactors due to the ongoing high dose rates, our hosts took us to the torus room of the undamaged Unit 5 containment, to show us where the containment vent valves were located on the damaged units. This was done so we could understand the difficulty the operators faced in trying to manually open the valves.

ericquote1I tried to picture the challenge for the operators, going into this confined area in pitch black, the heat stifling, the dose rate steadily increasing, looking for the valves they’d have to operate manually. The descriptions of the accident from the operators who lived through the ordeal will stay with me forever. Many of them truly believed they were going to die. They had no idea if their families survived the tsunami or where their families were. Yet they stayed and fought the accident. They were incredibly courageous.

I am more convinced than ever that the Fukushima lessons learned we are requiring the industry to implement are critical to ensure an accident like the one at Fukushima doesn’t happen here. We have to ensure the licensees fully implement, maintain, and exercise the Fukushima lessons learned. We have to make sure the licensees prepare their facilities and are ready to confront the unexpected. We are the ones who are accountable to and responsible for protecting the American public. It’s our job. For me, it’s personal. It’s what I’m here to do.

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