U.S. NRC Blog

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Category Archives: Operating Reactors

Examining the Reasons for Ending the Cancer Risk Study

Scott Burnell
Public Affairs Officer

One way NRC regulations protect communities around U.S. nuclear power plants is by requiring the plants to regularly sample air, water, and vegetation around their sites. Results of this sampling are sent to the NRC (and in some cases state agencies) to show only very tiny amounts of radioactive material are released during normal operations.

Even with this scrutiny — and a 1990 study showing no difference in cancer mortality rates between those living near U.S. reactors and those living elsewhere — questions persist about cancer risk from nearby reactors. The NRC had worked with the National Academy of Sciences (NAS) since 2010 on a study into the potential cancer risk of living near a U.S. nuclear power plant. But we ended this work earlier this month after a hard look at the low likelihood of getting usable results in a reasonable time frame.

radiationsymbolWhy are we comfortable that this decision, also driven by our budget situation, is in line with our mission to protect public health and safety?

First and foremost, the staff considered existing conditions around U.S. reactors, as shown by the ongoing environmental sampling and analysis we mentioned earlier. That evidence supports the conclusion that the average U.S. citizen’s annual radiation dose from natural sources, such as radon and cosmic rays, is about a hundred times greater than the largest potential dose from a normally operating reactor.

This information shows how complicated it would be to single out an operating reactor’s potential contribution to cancer risk. Researchers looking for small effects need a very large study population to be confident in their results. The NAS discussed this issue in its report on Phase 1 of the cancer risk study. The NAS said that the effort “may not have adequate statistical power to detect the presumed small increases in cancer risks arising from… monitored and reported releases.”

The NRC staff examined the NAS Phase 2 report plans to validate the methods recommended in Phase 1. The Academy was very clear that the pilot study at seven U.S. sites was unlikely to answer the basic risk question. The NAS proposal said: “any data collected during the pilot study will have limited use for estimating cancer risks in populations near each of the nuclear facilities or for the seven nuclear facilities combined because of the imprecision inherent in estimates from small samples.”

The pilot study would also examine potential differences between individual states’ cancer registries. Large differences in registry quality or accessibility would hurt the study’s chances of generating useful results.

The NAS concluded they would need more than three years and $8 million to complete the pilot study. If the pilot succeeded, expanding the research to all U.S. operating reactors would require additional years and tens of millions of dollars. The NRC decided that in our current budget environment the time and money would not be well spent for the possible lack of useful results.

The NRC agrees with the NAS that the study’s overall approach is scientifically sound. Interested individuals or groups can examine the NAS Phase 1 and 2 reports for a more detailed discussion of the methods and resources needed to conduct the proposed study. The NRC staff will examine international and national studies on cancer risk to see if we should conduct any future work in this area.

On the Wild Side at U.S. Nuclear Power Plants

Neil Sheehan
Public Affairs Officer
Region I

Examples abound of the ways in which nature abhors a vacuum. Raptors will set up shop on a skyscraper ledge, just as they will on a cliff, if it suits their needs. Coyotes have been increasingly spotted in urban settings, even roaming about the streets of Manhattan. Last year, surveillance cameras captured images of a mountain lion strolling the Hollywood Hills after dark.

This falcon is resting on equipment at the TMI nuclear power plant site. Photo courtesy of TMI

This falcon is resting on equipment at the TMI nuclear power plant site. Photo courtesy of TMI

Nuclear power plants are also home to a variety of wildlife. Despite the industrial nature of these facilities, they are usually situated on large tracts of land encompassing hundreds of acres. They are also adjacent to bodies of water in order to tap into that H20 for cooling purposes.

All of that property and access to water can entice a variety of animals and birds to take up residence on the sites. And they do just that.

Information supporting this can be found in the Post-Shutdown Decommissioning Activities Reports (PSDARs) for U.S. nuclear power plants that have ceased operations.

In the report for the Vermont Yankee nuclear power plant, which was submitted to the NRC in December 2014, it’s noted that the main emissions stack includes an attached nesting box for peregrine falcons. The box was installed by the company in 2009 at the request of the Audubon Society.

It’s been a rousing success, as according to the report “there have been two consecutive years of four young born and successfully fledged since 2012.”

Current decommissioning plans call for the Vernon, Vt., plant to be placed in storage for several decades prior to the initiation of major dismantlement work. However, when the time comes to remove the stack, the plant’s owner will need to consult with the U.S. Fish and Wildlife Service prior to removing the nesting box since the peregrine falcon is protected under the Migratory Bird Treaty Act.

Peregrine falcons can also be found at the Three Mile Island nuclear power plant, in central Pennsylvania. The PSDAR for TMI-2, where a severe accident occurred in 1979 and which won’t be taken apart until the neighboring TMI-1 permanently shuts down and is also ready for that work, shows peregrine falcons have nested on the TMI reactor building since 2002.

An osprey can be seen in flight at a nuclear power plant site.

An osprey can be seen in flight at a nuclear power plant site.

Meanwhile, the plant’s meteorological tower, which collects important weather data, has been home to an osprey nest every year since 2004. Ospreys, also referred to as fish hawks (with a wing span from around 5 feet), like to be around water, so it’s not surprising that TMI, situated on the Susquehanna River, is a place they call home.

A variety of wildlife can be found in the vicinity of the Crystal River 3 nuclear power plant, located on the Gulf Coast of Florida. That plant’s PSDAR, which the NRC received in December 2013, identifies the following threatened or endangered species in the vicinity of the site: Two species of fish — Gulf sturgeon and smalltooth sawfish; five species of sea turtles — green turtle, hawksbill, Kemp’s ridley, leatherback and loggerhead; one crocodilian species — American alligator; and one marine mammal — Florida manatee.

But on the site itself, only one state-listed threatened species, the bald eagle, and one state-listed endangered species, the wood stork, are found, according to the report. The PSDAR adds that three other species can “potentially occur” on the property: the gopher tortoise, the eastern indigo snake and the piping plover.

In the case of all of these plants and the others around the country, precautions must be taken to minimize the impacts of operations and decommissioning activities on these species and their habitats, consistent with federal and state laws.

Lining Up New Protections with New Flood Info

Lauren K. Gibson
Project Manager
Japan Lessons Learned Division

Walkdowns (3)The NRC is moving forward on connecting two important lessons we learned from the Fukushima nuclear accident in Japan: protecting key safety functions and reevaluating flood hazards. The agency’s ongoing work would require U.S. nuclear power plants to ensure their protection strategies account for updated flood levels.

The Commission has approved the staff’s plan for completing the reevaluated flooding hazards review. The staff’s plan also covers how U.S. plants must account for the new hazards in their mitigation strategies for beyond-design-basis events. The plan requires U.S. plants to determine which flood hazard data could affect their strategies. We believe this approach is the quickest way to provide the most significant flood protection improvements.

The NRC assesses plants’ re-evaluated flood hazards to see whether the re-evaluated hazards were properly calculated. Plants need these assessments to evaluate their strategies against the re-evaluated hazard. We’re still reviewing some plants’ work; we’re issuing interim letters so those plants know how to follow the rest of the staff’s plan.

The plants examine whether their strategies work under the new hazard conditions and make any appropriate adjustments. For example, a strategy might require a pump in a location submerged by the new possible flood level. The plant would then consider options such as relocating the pump. These assessments and adjustments would be substantially complete by 2016.

The second part of completing the flooding hazard work involves either a focused evaluation or a broader integrated assessment of the plant’s protection capabilities. The specific work depends on:

  1. Which hazards, if any, cause flood levels higher than the plant’s original level.
  2. Whether the plant’s flood protections have available physical margin. (For example, if the new flood hazard level is six feet and a plant’s existing wall is seven feet tall, the wall has available physical margin to handle the new flood level.)
  3. Whether the higher flooding levels disable the plant’s ability to cool the reactor core or spent fuel pool, or protect containment.

If the local intense precipitation hazard is the only cause of a higher level, then the plant performs a focused evaluation. If other flooding hazards are involved, but the plant has available physical margin and can maintain safety functions, then the plant only needs a focused evaluation. The focused evaluation would identify any physical or procedure changes needed to address the new flood level. We would review and inspect these changes to ensure they resolve the issue.

The remaining plants would perform an integrated assessment, looking at all flooding hazards and identifying any changes needed to protect the plant from the new hazard. We’ll review these assessments and decide if voluntary plant actions would be effective or if the NRC must order plant changes.

You can find out more information about Recommendation 2.1—Flooding on the Japan Lessons Learned portion of the NRC website.

A Monday Quiz — A Blue Glow

The Advanced Test Reactor at Idaho National Laboratory uses plate type fuel in a clover leaf arrangement. The blue glow around the core is known as Cherenkov radiation. Courtesy of Idaho National Laboratory.

This Advanced Test Reactor runs tests that determine how fuels and materials react when bombarded by streams of neutrons and gamma rays under a variety of pressure and temperature conditions. Information that would normally require years to gather from normal reactor operations can be obtained in a matter of weeks or months. The primary “customer” of the reactor is the Naval Nuclear Propulsion Program.

The NRC licenses 31 research and test reactors in 21 states (as of 2014); eight research reactors are being decommissioned. We also license the operators and conduct some 50 inspections each year. DOE, however, regulates this particular test reactor.


Where is this test reactor located?
What scientist (and Nobel Prize winner) gave his name to the blue glow seen in this photo?


NRC — Ready for the 2015 Hurricane Season UPDATED

Update: Due to Hurricane Bill, the South Texas Project nuclear power plant, located near Bay City, Texas, has started tropical storm/hurricane procedures. Actions taken include performing a plant walkdown to secure and tie down anything that could be become a projectile missile or flying debris. The plant operator has implemented restrictions for employees to stay inside if winds get above 40 mph. Today, winds are projected to be sustained at 50 mph with gusts up to 60 mph. Both units are at full power unless winds reach speeds above 75 mph, but that is not expected at this time. They have additional staff onsite and supplies (cots, food, water). The resident inspectors are not evacuating and an additional group of NRC inspectors has been on site and will remain so to back up the residents if need be. (At this time the hurricane is not expected to affect River Bend or Waterford nuclear power plants, but the NRC’s Region IV will continue to monitor the projected path.)

Roger Hannah
Senior Public Affairs Officer
Region II

The hurricane season officially began June 1, but this year the Carolina coast experienced a tropical storm named Ana in early May. While Ana produced winds of more than 60 miles an hour near the Brunswick nuclear plant, there was no major damage. It did, however, serve as an early reminder of the NRC’s role in ensuring nuclear plants remain safe during damaging winds and storm surges.

A hurricane as seen by satellite. Be assured, it's not happening now.

A hurricane as seen by satellite. Be assured, it’s not a current photo and is NOT happening now.

The NRC has years of experience with hurricanes and other severe storms. Nuclear facilities were affected by Hurricane Andrew in Florida in 1992, by Katrina in Louisiana in 2005, by Sandy along the East Coast in 2012 and by many others. Although the National Oceanic and Atmospheric Administration predicts fewer storms this year than the historical average, any storm can be dangerous.

How does the NRC oversee the safety of nuclear plants and other facilities during these storms?

The NRC staff monitors tropical storms as they form, and if the projected path is towards the coast, the agency’s regional offices begin continuous tracking. If a storm’s path shows the possibility of it affecting a nuclear plant or other NRC-licensed facility, the NRC collects more information on the storm and NRC resident inspectors check the plant’s preparations. Depending on the projections, additional NRC inspectors may be dispatched to some nuclear plants.

Around 12 hours before predicted hurricane-force winds, nuclear facilities that may be in the path provide the NRC updates and NRC inspectors monitor the plant staff’s actions. Plant procedures require the plant operators to shut the reactor down if winds greater than a certain speed are expected on the plant site.

Nuclear plants are built to withstand all expected local meteorological events, including hurricanes, and actual storms have shown that plants can safely shut down and with little or no damage to important safety equipment.

The NRC stays in contact with plants and NRC inspectors on site as the storm passes over, and the agency has backup systems if regular communications channels are lost.

Once the storm is over, the NRC and FEMA assess damage and make sure local emergency response organizations can resume their normal roles. If the plant shut down, it will only be restarted after the NRC is satisfied there is no damage to safety equipment and emergency response capabilities have been restored.

Fortunately, most tropical storms and hurricanes do not adversely affect nuclear plants, but the NRC is ready in case one does.


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