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Category Archives: Operating Reactors

April Showers Also Bring Seasonal Power Plant Refueling Outages

Neil Sheehan
Public Affairs Officer
Region I

 

The robins are chirping, the daffodils are pushing out of the cold ground and the sun is shining for an additional minute or two every day. It’s finally spring in the U.S., which for many nuclear power plants heralds the start of refueling and maintenance outages.

npp2Every 18 to 24 months, nuclear power plants shut down to allow for the replacement of about a third of the fuel in the reactor with fresh rods. The outages also make it possible for plant personnel and contractors to perform a number of projects, such as the refurbishment or replacement of pumps and valves, and inspections of components not accessible when the reactor is operating.

Hundreds of contractors assist with this work, making these outages periods of intense, round-the-clock activity for at least several weeks. No doubt nearby coffee shops do a booming business, not to mention area hotels and restaurants.

The NRC also beefs up its inspection footprint during these shutdowns, which are usually scheduled for spring and fall because those are the times when the demand for electricity is generally lower. Resident Inspectors assigned to the plant on a full-time basis and specialist inspectors observe select work activities to ensure adherence to safety regulations. They are also able to glean information about what employees and contractors are learning as they put eyes on key pieces of equipment.

There are procedures that help guide NRC inspectors during outages, including one that helps target and prioritize areas for review. A key, though, is remaining flexible while maintaining a holistic view of what almost overnight becomes a particularly bustling workplace.

Nuclear power plants are baseload electricity generators designed to run at 100 percent, but they need to occasionally take a strategic timeout to refuel and kick the tires, so to speak. With careful planning, a focus on safety and an attention to detail, the tasks can be effectively completed and the unit restored to service in time to help meet the additional cooling demands of the ensuing summer or the warming needs of the following winter.

 

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.

Spring Is Annual Assessment Time at the NRC

David McIntyre
Public Affairs Officer
 

cherrytreeSpring is here at last, and with it the season of NRC’s annual assessments of nuclear power plant performance during the previous calendar year. The Office of Public Affairs is issuing press releases faster than trees drop pollen announcing public meetings in the vicinity of each plant to update residents on how their local plants performed.

These meetings are routine, in that we hold them every year. Yet they are important, because they represent a report card of sorts on plant safety and because they give the agency a chance to reach out to its most important stakeholders — the people who live near the plants and have the highest stake in their safe operation.

The annual assessment letters were issued to the plants earlier this month. And the grades were mostly good. As of the end of December, 89 of 100 operating commercial nuclear reactors were in the two highest performance categories. Of those, 80 were in the highest level, with nine others requiring some additional oversight to correct issues of low safety significance. Another nine were in the third category, requiring even more oversight to correct what we call “degraded” performance.

More good news though – between December 31 and the time the assessments were issued, four of these 18 reactors in the lower second and third column had resolved their issues and moved back into the top category.

One reactor, Browns Ferry 1 in Alabama, is in the fourth performance category. It requires increased oversight because of a safety finding of high significance – including additional inspections to confirm the plant’s performance issues are being addressed.

Finally, Fort Calhoun plant in Nebraska is currently under a special NRC oversight program distinct from the normal performance levels because of an extended shutdown with significant performance issues. The plant remains under special oversight even though the NRC approved its restart last December.

You can find the report card for your local plant on the NRC website’s Reactor Oversight Process page. Just click on the plant’s name in the left-hand column, then look for the 4Q/2013 assessment report on the plant’s individual page. Here you will also find each plant’s current placement in the NRC action matrix, along with performance indicators and inspection findings. Press releases about when your local plant’s assessment meeting will be held can be found here.

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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