By Brian Wheeler
As Tropical Storm Isaac, eventually becoming Hurricane Issac, slowly moved across the Gulf Coast en route to the same area of the continental U.S. that was devastated by Hurricane Katrina just seven years prior, electric utilities throughout the Southeast were preparing to respond to widespread power outages. Owners and operators of nuclear power plants in the region also had to ensure plants were safe from hurricane-force winds.
|Florida Power & Light Company crews work to rebuild the electric grid after Hurricane Andrew in 1992. Photo courtesy of Florida Power & Light Co.|
Hurricane Sandy struck the East Coast Oct. 29 and left millions of homes and businesses without power. A half dozen nuclear plants were affected by the storm. The Oyster Creek nuclear plant in New Jersey was placed on “alert” status while three other nuclear reactors were forced to shut down due to complications caused by the superstorm. Overall, though, the nuclear industry weathered the storm without any major problems. According to the Nuclear Energy Institute (NEI), 34 out of 104 U.S. nuclear reactors were in the path of Sandy. Out of 34 reactors, 24 continued to generate power safely during the course of the storm.
Prior to a hurricane making landfall, plant operators take necessary precautions as mandated by the Nuclear Regulatory Commission’s (NRC) guidelines and the plant’s own emergency preparedness plans, according to the NEI.
About 120 hours before the storm makes it to the U.S. coastline, the NRC begins constant hurricane tracking at one or more of its four regional offices in Pennsylvania, Georgia, Illinois and Texas. About 48 hours before hurricane-force winds, the NRC will dispatch officials to State Emergency Operations Centers. About 12 hours out, NRC will enter either a “Monitoring” or “Activation” mode and begin receiving updates from all operators of nuclear plants within the storm’s projected path.
Reactor containment structures of steel-reinforced concrete are built to withstand hurricanes and plant personnel continuously monitor storm conditions. Some utilities, such as Florida Power & Light (FPL), have a meteorologist on staff due to the nature of its service territory. As Isaac approached Florida, FPL staff completed full walk-downs at both the St. Lucie plant and the Turkey Point plant. Peter Robbins, spokesperson for FPL, said employees locked down equipment to make sure the sites were physically ready for the storm. Robbins said FPL will shut down nuclear units at least two hours prior to the arrival of hurricane-force winds, typically between 70 and 75 miles per hour.
“We leave those units shut down after the storm passes and the sites have been inspected,” said Robbins.
For FPL, prepping for a hurricane’s arrival is not out of the ordinary. The same week Isaac was approaching the U.S. coastline, FPL was recognizing its employees for their work during the most powerful hurricane ever to hit a nuclear plant, Hurricane Andrew in 1992. FPL safely shut down Turkey Point Units 3 and 4 and emergency generators were used for six days after Andrew.
“Twenty years ago this week, Turkey Point took a direct hit from Hurricane Andrew,” Robbins said in an interview while FPL prepped for Isaac. “There was no damage to nuclear components and the reactor had no damage.”
Jackson, Miss.-based Entergy Corp. is also no stranger to hurricanes. In 2005, Entergy’s service area was hit by both Hurricanes Katrina and Rita. Katrina made landfall Aug. 29, 2005, as a Category 4 hurricane with winds touching 140 mph. Twenty-six days later, Category 3 Hurricane Rita struck Entergy’s service area creating 810,000 outages, the second worst ever for Entergy.
Entergy owns and operates 12 reactors at 10 sites. Three of those sites are in or near the areas affected by Katrina and Rita, and were also in the path of 2012’s Isaac. The single-unit, 1,159 MW Waterford 3 plant is about 20 miles west of New Orleans; the single-unit 974 MW River Bend is about 25 miles northwest of Baton Rouge, La.; and the single-unit, 1,071 MW Grand Gulf plant is near Port Gibson, Miss.
When Katrina went through the New Orleans area, off-site power was disrupted at the Waterford station on Aug. 29, 2005. The plant’s diesel generators maintained power for reactor cooling, auxiliary systems and other functions until the lines were reconnected on Sept. 2, 2005.
“It demonstrated the capacity of a U.S. nuclear site to maintain safe operations even when disconnected from off-site power and the grid,” said Mike Bowling, spokesperson for Entergy. “Safety systems and emergency plans functioned as they were designed to, during and after the hurricane.”
According to NEI, if there is a loss of off-site power during or following a hurricane, as there was at Waterford 3 during Katrina, reactors will automatically shut down as a precaution and emergency backup diesel generators will begin operating to provide electrical power to plant safety systems. As part of the pre-storm inspection, diesel fuel tanks are checked and topped off to ensure there is a minimum of seven days of fuel to power the generators.
|The Waterford 3 nuclear power plant in Louisiana was shut down prior to Hurricane Isaac’s arrival. Photo courtesy of the Nuclear Regulatory Commission and Entergy Corp.|
Further enhancing safety in response to the disaster at the Fukushima Daiichi nuclear plant in Japan, NEI in February said nuclear plant operators approved an initiative, known as FLEX, to purchase additional on-site portable equipment. Operators, at the time, had acquired or ordered more than 300 pieces of equipment to supplement layer upon layer of safety at U.S. sites. The equipment ranges from diesel-driven pumps, generators, ventilation fans, hoses, fittings, cables and communications gear. NEI said the approach adds flexible coping capability that will provide a backup to permanently installed plant equipment that would be available following extreme events.
“An extended loss of AC power is critical to being able to cope with,” Tony Pietrangelo, senior vice president and chief nuclear officer at NEI, said during a press conference announcing the FLEX approach.
As Isaac was upgraded to a Category 1 hurricane on Aug. 28, Entergy safely shut down the Waterford 3 plant in advance of the arrival of Hurricane Isaac. The plant is designed to withstand 200 mph winds. Entergy’s procedures call for the utility to demonstrate its ability to respond, conduct plant walk downs and equipment checks, and implement staffing plans.
Entergy’s procedure also calls for a controlled, safe shutdown in advance of hurricane-force winds at a nuclear plant site, said Bowling.
The proximity of the hurricane and the potential impact on grid stability were considerations in making the decision to shut down the plant, he said.
“The procedures are pretty comprehensive,” said Bowling. “There is a technical component and a people component to our preparations.”
Hurricane season could seem like a short timeframe for those who don’t live in areas impacted by the storms, but hurricane season can span a large portion of the year. According to the National Hurricane Center, hurricane season in the Atlantic begins June 1 and ends Nov. 30, with the Eastern Pacific hurricane season beginning May 15 and also ending Nov. 30.
“We are in hurricane alley,” said Bowling. “We have emergency procedures at each site that allow us to respond to storms.”
|Diagram providing cutaway view of a nuclear reactor containment structure designed in the United States and approved by the U.S. Nuclear Regulatory Commission. Photo courtesy of the Nuclear Energy Institute.|
While much of the preparation deals with the technical side of the plant, having staff prepared and trained is critical. As Bowling said, there is a people component to hurricane preparations. According to NEI, nuclear plant operators at all sites train one out of every six weeks on how to safely manage extreme events, such as hurricanes, and regularly coordinate with local, state and federal officials to prepare for emergencies. Bowling said Entergy trains with specific scenarios in which the utility has oversight from the Federal Emergency Management Agency (FEMA) and the NRC.
“Operators are trained on a regular basic,” said Bowling. “We are observed, given feedback and all discuss how to get better.”
FPL also prepares their staff for storm season. Robbins said FPL has a company-wide, week-long storm drill that tests every part of the organization.
“We do this every year to test our storm plan,” he said.
At its peak, Hurricane Isaac knocked out power to more than 787,000 Entergy customers in Louisiana, Arkansas, and Mississippi, making it the fourth most damaging storm in the utility’s history in terms of outages. Entergy said its total restoration costs for the repair and/or replacement of the electrical facilities in areas with damage from Isaac are estimated to be in the range of $400 million to $500 million. Entergy’s Waterford station, along with the River Bend plant, provided shelter for about 100 core employees during Isaac. Just two days after being safely shut down, Entergy was preparing to restart Waterford. No damage was reported at any of the facilities, and on Sept. 3, Entergy reconnected the Waterford plant to the grid. To bring the undamaged plant back online, Entergy’s plan called for coordination with FEMA, the NRC and local authorities.
Prior to resuming power, Entergy said operators completed a checklist that involved verifying that evacuation routes were open, that communication channels with public officials and emergency facilities were intact and that the public alert siren system was functioning properly.
“Once again, our ongoing efforts to maintain a high state of readiness to respond to any emergency proved successful,” said Waterford site vice president Donna Jacobs.
On Sept. 5, Waterford 3 reached 100 percent power.