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

The Palisades’ Shutdown Explained

The Palisades nuclear plant in Michigan shut down Sunday after workers noticed steam leaking from a drain valve on the piping from one of the reactor’s two steam generators. The shutdown was uneventful, and the NRC has no immediate safety concerns with this issue.

Here’s what happened: The workers were touring the plant’s auxiliary building when they noticed the leak early on Sunday. The leak was in the “secondary” part of the steam generator, not part of the reactor coolant system.

Because the valve could not be isolated from the rest of the steam generator system, the steam generator had to be declared inoperable. The plant’s technical specifications require the licensee, Entergy, to shut down the reactor within six hours when a steam generator is inoperable. Plant operators completed the procedure by 4:30 p.m., meeting this requirement.

The NRC’s resident inspectors responded to the site, observed portions of the shutdown, and made sure there was no impact on other plant equipment.

As the plant cooled, pressure dropped within the steam system, and that stopped the leak. The steam condensed, and the water was collected. It contained small amounts of radioactive tritium, but at levels far below regulatory limits. It will be disposed of as low-level radioactive waste. After shutting down, plant operators vented steam from the same system into the atmosphere through an established monitored release path. This is a common procedure used to help the plant cool down in order to begin repairs.

Palisades remains in cold shutdown while Entergy workers repair the leaky valve. NRC’s inspectors will monitor and assess the repairs, which are expected to take a few days.

David McIntyre
Public Affairs Officer
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