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Category Archives: Operating Reactors

Senior Earthquake Experts Help Analyze Palo Verde Risk

Brittain Hill
Senior Advisor
Office of New Reactors

The NRC regularly works with outside experts when we examine technical issues, including earthquake hazards. We’ve just reviewed how the Palo Verde nuclear power plant in Arizona used experts as it re-evaluated its quake hazard. We’re satisfied with the results.

pv-from-mountainsFor almost 20 years the agency has used the Senior Seismic Hazard Advisory Committee approach to consider a broad range of information in earthquake hazard analysis. Western U.S. nuclear power plants have followed this method to help meet the NRC’s post-Fukushima effort to re-evaluate their quake hazards. Palo Verde, the Columbia power plant in Washington and the Diablo Canyon power plant in California each used a detailed SSHAC process to better understand where quakes could occur and how quake energy causes the ground to move at their site.

Different kinds of uncertainty make earthquake analysis difficult. Quakes are random in many ways, and quake science is incomplete. The SSHAC approach is valuable because it effectively includes both types of uncertainty in the analysis.

Palo Verde started the process with a series of expert workshops in 2013 and 2014. The workshops identified and gathered the best available information, and then moved on to discuss how best to analyze that data. NRC staff observed the workshops and reviewed the written results of this work, concluding the plant correctly used the SSHAC process.

The plant examined historic quakes out to about 250 miles from the site, including large quakes in southern California and northern Mexico. Both Palo Verde’s effort and the NRC staff’s independent analysis found about 900 quakes to consider. While the plant later found it used some incorrect values in examining those quakes, additional plant analysis and independent NRC calculations found the correct values slightly decreased the site’s quake hazard.

All of this leads the agency to conclude Palo Verde developed an appropriate model for quake sources around the site.

The plant also reviewed U.S. and international databases and numerical models of ground motions in areas similar to Arizona. Palo Verde’s effort also considered how nearby California and Mexico quakes could affect the site’s ground motion. From there, the plant calculated likely quake hazards of different strengths and the resulting ground motions at the site. As with the other parts of the re-evaluation, the NRC staff did independent calculations and concluded the plant’s approach was appropriate.

The NRC’s overall review reaches the conclusion that Palo Verde is designed to withstand future quakes in its area, so the plant has completed its seismic re-evaluation. We’ll give the Columbia and Diablo Canyon re-evaluations the same sort of scrutiny to ensure they’re able to withstand future quakes in their areas. The NRC’s website has more information on the overall re-evaluation effort.

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

Update: At nuclear power plants in the southwest, snakes, scorpions and black widow spiders are not an unusual sight. Resident Inspectors have to be especially careful during their walkthroughs in those plants not to poke into areas between pipes or bundles of electrical cables where venomous critters may be nesting.  But the most exotic wildlife may be the denizens at the South Texas Project nuclear plant in Bay City, where alligators abound. “We usually have about 75 alligators roaming around on site here at any given time,” said Shelia Davis, a corporate communications specialist for the South Texas Project. “If they stray into areas where they shouldn’t be we have people who are specially trained and can move them safely to our 7,000 acre reservoir.” Victor Dricks

Neil Sheehan
Public Affairs Officer
Region I

refresh leafExamples 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.

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 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.”

An alligator crossing sign at the South Texas Project nuclear power plant.

An alligator crossing sign at the South Texas Project nuclear power plant.

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.

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.

REFRESH is an occasional series where we rerun and/or update previous blog posts. This post first ran in August 2015.

When A Plant Changes Hands

Neil Sheehan
Public Affairs Officer
Region I

FitzPatrickTowerViewIn February, Entergy announced plans to permanently shut down the James A. FitzPatrick nuclear power plant on Jan. 27, 2017. However, there are indications – based on recent negotiations between Entergy and Exelon – that the facility may not cease operations after all.

On Aug. 9, Exelon announced it had reached a deal to purchase the Scriba (Oswego County), N.Y., boiling-water reactor from Entergy for $110 million. This agreement occurred after the New York State Public Service Commission approved Zero Emission Credits, or subsidies, which will help upstate N.Y. nuclear plants stay online amid historically low energy prices.

Challenging market conditions had earlier prompted Entergy to announce the plant’s closure. The NRC in 2008 had approved a renewal of FitzPatrick’s initial 40-year operating license, extending it until October 2034.

Before the sale of the plant can be completed, the transaction will undergo reviews by the NRC, as well as other regulatory agencies. NRC staff will evaluate Exelon’s technical and financial capabilities to ensure the plant’s safe operation and to provide reasonable assurance that adequate funding is available to safely decommission the unit after the final shutdown has occurred.

Exelon currently owns and operates 22 reactors at 13 plant sites in the U.S. The company also runs Fort Calhoun under a contract with the Omaha Public Power District.

We will publish on our website and in the Federal Register a notice of having received the license transfer application, dated August. 18, and the opportunity to request a hearing on the proposal. As for the process itself, such reviews generally take from six months to a year. For example, when the FitzPatrick operating license was transferred from the New York Power Authority to Entergy in 2000, the review was completed in about half a year.

As a footnote, Exelon already owns the Nine Mile Point nuclear power plant, which is located next-door to FitzPatrick.

NRC Keeps an Eye on Gulf Coast Flooding

Victor Dricks
Senior Public Affairs Officer
Region IV

Torrential rains have been battering the Gulf Coast since Friday, but have not adversely affected any of the nuclear power plants in Louisiana, Mississippi, or Arkansas.

louisiana map_sealThough skies have now cleared over Baton Rouge, the area has been especially hard hit by flooding. But this has had no significant impact on the River Bend nuclear power plant, about 25 miles northwest of the city, or the designated routes that would be used to evacuate the public in the event of a nuclear emergency.

The Waterford 3 nuclear plant, located in Killona (about 25 miles west of New Orleans), has been similarly unaffected. “We’ve had some heavy rain here over the weekend but there has not been any real impact on the plant,” said NRC Resident Inspector Chris Speer.

Flooding is one of the many natural hazards that nuclear power plants must be prepared for. Every nuclear power plant must demonstrate the ability to withstand extreme flooding and shut down safely if necessary. Most nuclear power plants have emergency diesel generators that can supply backup power for key safety systems if off-site power is lost.

All plants have robust designs with redundancy in key components that are protected from natural events, including flooding. These requirements were in place before the Fukushima accident in Japan in 2011, and have been strengthened since.

As of Tuesday, Arkansas Nuclear One, in Russellville, has gotten about five inches of rain since Friday, NRC Resident Inspector Margaret Tobin said. “It’s a little muddy at the site, but that’s about it.”

At Grand Gulf plant in Mississippi, 20 miles southwest of Vicksburg, only light rain has been reported. “We actually had very little rain at the site, compared to what was expected,” said Matt Young, the NRC’s Senior Resident at the plant.

The NRC is closely following events and getting periodic updates from the National Weather Service on conditions that might affect any of the Gulf Coast nuclear plants. Additionally, the resident inspectors are monitoring local weather conditions to remain aware of conditions that could affect continued safe operations of the plants.

REFRESH: The Power of Power Uprates

Since this blog post first ran in December 2011, the NRC staff has approved 16 additional power uprates, increasing the nuclear fleet’s output by an additional 1300 megawatts electric. An additional three are under review (for the three reactors at Browns Ferry), and the staff expects to receive an additional 10 uprate applications through the end of September 2017.  David McIntyre

Neil Sheehan
Public Affairs Officer
Region
I

refresh leafMuch news space has been devoted over the years to the prospects for new reactors in the U.S. However, new reactors are not the only way the nation’s share of nuclear-generated electricity can be increased — and it doesn’t involve earth-movers, the construction of new buildings or other changes visible to the casual observer.

Another option available to nuclear power plant owners is to pursue a power uprate, which essentially means an increase in the maximum amount of power a reactor can generate. But before a power uprate can be implemented, it must first undergo a thorough review by the NRC.

Take for example, the NRC’s approval of a 15 percent power uprate for the Nine Mile Point 2 nuclear power plant in upstate New York. That approval was the culmination of an NRC review that began with the submittal of the application on May 27, 2009.

During the course of the agency’s evaluation of the proposal, NRC staff scrutinized data regarding the proposal and posed dozens of technical questions to the plant’s owner, Constellation. They included queries about the effects of greater stresses on piping and the plant’s steam dryer, a component at the top of the reactor vessel, as a result of operations at higher power levels.

Power_Uprates_past-current-future (002)The NRC does not proceed to a final decision until all such questions are answered to our full satisfaction.

Uprates are not a new development. In fact, the NRC approved the first uprate back in 1977 and has to date approved 140 such applications. All told, the uprates have led to an increase in power output nationwide of about 6,000 megawatts electric.

There are three different kinds of power uprates: “measurement uncertainty recapture” uprates, “stretch” uprates and “extended” uprates. Here’s a brief description of each:

Measurement uncertainty recapture uprates – They involve an increase of less than 2 percent and are achieved by implementing enhanced techniques for calculating reactor power levels. State-of-the-art devices are used to more precisely measure feedwater flow, which is used to calculate reactor power.

Stretch uprates – The increases are typically between 2 and 7 percent and usually involve changes to instrumentation settings but do not require major plant modifications.

Extended uprates – Power boosts of this type have been approved for increases of up to 20 percent. They usually involve significant modifications to major pieces of non-nuclear equipment, such as high-pressure turbines, condensate pumps and motors, main generators and/or transformers. The Nine Mile Point 2 uprate would fall into this category.

For more information on power uprates, visit the NRC web site.

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