Be Prepared is Also the Motto of U.S. Nuclear Plants

Hurricane Sandy devastated homes, but did not damage nuclear power plants in its path. Photo: Courtesy of FEMA

Whenever severe weather events occur – such as last week’s Hurricane Sandy – it always prompts questions about how nuclear power plants are prepared to handle them.

The answer is always the same: Every U.S. nuclear plant has a list of severe weather conditions that require it to shut down as a precaution. But because these plants are built robustly, and built to withstand the expected forces of nature in the area, they don’t necessarily have to shut down in the face of severe weather. It all depends on their specific criteria.

For example, forecasts of hurricane-force winds within 24 hours or expected storm surges greater than a given height may trigger a plant’s shutdown criteria and allow them time to get backup systems ready. But even if an area experiences strong or damaging storm conditions, a plant in that area may be designed to continue operating to help the electric grid power essential services such as hospitals and police and fire stations. However, plants would shut down or reduce power if the electric grid was damaged.

In addition to protections again wind, every U.S. nuclear plant is designed to withstand severe flooding (and storm surge for coastal plants), and key components and systems are protected by watertight buildings capable of withstanding major hurricane-force winds and flooding.

Sandy is just the latest storm to pass near nuclear plants without significant impact. For example:

• In 2005, the Waterford 3 plant in Louisiana remained safe after Hurricane Katrina knocked out the plant’s connection to the electric grid. Waterford ran its safety equipment on emergency diesel generators and remained safe once it reconnected to the grid four days later.

• In 2004, both reactors at the St. Lucie site in Florida remained safe after Hurricane Jeanne knocked out the plant’s grid connection. The plant’s staff manually shut down the reactors properly and all emergency equipment, including the diesel generators, ran as expected to keep the plant safe.

• In 1992, both reactors at the Turkey Point site in south Florida remained safe after Hurricane Andrew, one of the most powerful hurricanes to hit the United States, passed directly over the plant and knocked out the area’s electrical infrastructure. Turkey Point’s emergency diesel generators ran for six days.

NRC regulations ensure that nuclear power plants can remain safe even during a hurricane and loss of outside power to run safety systems. The sites keep about a week’s worth of diesel onsite for the emergency generators, and the utilities typically have agreements in place that give them priority in getting more diesel to the sites if necessary. The diesel generators sit in buildings designed to safely withstand just as much punishment as the reactor safety systems.

These regulations were enhanced after 9/11, when the NRC required U.S. plants to put in place additional portable generators and pumps. During Sandy, the Oyster Creek plant had those additional resources available but ended up not needing them. In the wake of Fukushima, the NRC has ordered the plants to obtain even more portable equipment and make sure it’s protected from severe weather and other events.

All of this effort helps ensure that the public remains safe even if a hurricane, nor’easter or blizzard affects a nuclear power plant near you.

Scott Burnell
Public Affairs Officer

Author: Moderator

Public Affairs Officer for the U.S. Nuclear Regulatory Commission

15 thoughts on “Be Prepared is Also the Motto of U.S. Nuclear Plants”

  1. nuclear guy, thanks for a helpful answer. I have heard some plants load their DGs by backfeeding the grid as load. Is that generally true, it seems like it could be putting critical engine control systems at risk.

  2. Then why did South Texas nuke have to force a worker to drive through flood waters to get food after just 1.5 days?

  3. The most recent entry is 2012?!!!!!!!!! What about Hurricane Matthew in 2016???? This is incredible. This is the agency that we’re supposed to trust to guard public health and safety???????!!!!!!!!!!

  4. Failure rates are vital to a plant’s safety analysis. It determines how much additional testing the diesels need, and also is part of what determines how long a plant is required to survive without electrical power (Station blackout per 10CFR50.63 and its associated reg guides). I would have to do some searching to find allowable failure rates and requirements, but it comes out to above 95% success on diesel starts for each individual diesel.

  5. The cooling towers do not provide safety related cooling and are not required to function during plant accidents or loss of power. Emergency cooling water is directly drawn and discharged from the local water source (river I believe). So yes, those cooling towers are assumed to be destroyed during accident analysis. They are only there to cool the condenser (non-nuclear) side of the plant.

  6. I live 100 miles downwind of the Plant Vogtle Nuclear Disaster on the Savannah River. I’m in Charleston, SC, home of the left over Polaris nuclear weapons dump noone else wants in their back yard.

    The NRC regional inspector has assured me Plant Vogtle’s 2 old reactors have “several days” of diesel fuel for the 4 gensets when, not if, another Hurricane Hugo, which destroyed Charleston in 1989, passes over Plant Vogtle. Hurricane Hugo took MONTHS to clear the roads so a refueling tractor trailer rig could get anywhere near this plant build in dense forest, that, I promise you, will be blown away by another Cat 5 like Hugo. I passed right through the eye of Hugo and watched 100 ft pine trees blow down our streets.

    I’ve asked Southern Co how much wind heavy with trees, cars, houses, boats, and anything else that’s not heavily anchored those VITAL cooling towers at Vogtle can handle in a Hugo that blew the swing bridges off their foundations. They wouldn’t answer. They don’t know.

    This is so important as the slow flowing Savannah could never provide the huge amount of water to col the plant, which is why they have cooling towers open to the air….even worse when the two new AP1000 monsters are also hot and demanding cooling water in addition to the old plant reactors.


  7. So each reactor at all US plants has a weeks worth of diesel on site now according to the new NRC guidelines. Is that right?

  8. Each reactor must have redundant emergency power sources to run all safe shutdown equipment – in other words, more than one emergency diesel generator. Many plants have two diesels per reactor, and there are cases where single emergency diesels at two co-located reactors are both supported by a third or “swing” diesel. Beyond that, each reactor has a “station blackout” generating source that steps in if the grid and “regular” diesels are unavailable at the same time. For example, during the August 2011 Virginia earthquake, the North Anna plant brought its station blackout diesel generator online as a redundancy after the quake when one of the site’s four emergency diesels was shut down as a precaution.

    To clarify other comments regarding emergency diesel generator inspection and maintenance requirements, the NRC’s guidance shows diesels are regularly tested “under load” to confirm they can meet all the power needs of safe shutdown equipment. For more information:

    Click to access 01-009.pdf

  9. Hey Lily, if you don’t mind me answering again, the requirements are different from plant to plant. You can see them on the operating license for each plant on the NRC web page. Start here (, pick a plant, then go to Plant Opearting License. It is in the technical specifications appendix, usually in the Electrical Systems section under the title Diesel Oil Storage or something. Some plants only list the amount of fuel required in gallons, but the tech spec basis (sometimes included in the license) will tell you how many days that equates to.

    Some older plants, like Oyster, are only required by operating license to have 3 days of fuel per generator. I know Oyster also has a large fuel storage tank with over 2 weeks total, but it is not an operating license requirement (may be some other commitment that requires them to have that, like station blackout requirements or PRA/risk requirements). Many plants conform to reg guide 1.137 (, which endorses ANS standard 59.51 which requires a minimum of 7 days of fuel OR the minimum amount required until a fuel supply can be arranged, whichever is greater. Many plants also have allowances to go below 7 days (down to 6 for example), provided they are only down to 6 for testing purposes, and they have fuel shipments ordered which will arrive on site within some time period (usually 24 hours of the test run). This allows plants to do their 24 hour test runs on the generator without having to enter their operating license limiting conditions.

  10. EDGs have multiple sets of testing requirements. The main ones are a monthly test requirement where the generator is slow started, placed on the regional power grid, and gradually increased in power to prove that it can handle full load. The next main requirement is for (roughly every 1-2 years), the generator to actually undergo a cold quick start where it has to rapidly come online and begin loading within its ECCS time requirements. There is also a requirement to do a 24 hour uninterrupted run on each generator, and I think it is on a similar 1-2 year frequency.

  11. Thanks for providing this information. Do all plants keep about 1 weeks worth of diesel or is this a heightened measure for those in hurricane areas? Is there a way to inform the public about how many total diesel generators a given plant has on site? That could considerably help people understand things when conditions at a plant become a concern for some reason. I had a couple of people ask me very worried about generators at Oyster Creek. At one point the number of generators was finally listed either by the NRC or by the operator to the media. That let people know there was more than one generator available there. Updating people about the successful addition of some of this new post-fukushima equipment or things like more batteries being installed could help those near the plants know where things are progressing. Someone asked me about battery inventory improvements and I really wasn’t sure where any of the plants were in that process.

  12. Thank you for the information. It has been reported that the NRC is also requiring additional stocks of gasoline at reactors in case more time is needed to keep backup systems in operation during emergencies. Is that correct?

  13. That doesnt make sense “allows them time to get backup systems ready”
    Sheesh, if its a backup system, it ought to be ready 24/7

    I heard your EDGs don’t get tested under load and operating the actual emergency circuits they would need to operate in practice. Please comment on this.

Comments are closed.

%d bloggers like this: