Nuclear power plant flood risk: Sandy was just a warm-up

Dec. 19, 2012 — As Hurricane Sandy approached the East Coast late last October, more than a dozen nuclear power plants from North Carolina stretching up to New England were in its wide-ranging path. On Oct. 29, the night that the eye of the storm made landfall near Atlantic City, New Jersey, five nuclear plants were forced to either reduce power or make emergency shutdowns.

The most serious event was at the Oyster Creek Generating Station located in Lacey Township, near Barnegat Bay, New Jersey, about 40 miles north of Atlantic City. Amid 75-mile-an-hour winds, power to the region was knocked out, including at the Oyster Creek plant, just before 7 p.m. The plant’s backup diesel generators kicked on to keep its crucial cooling equipment functioning. Nevertheless, by 9 p.m. the plant’s pumps were facing another danger: rising floodwaters. Nuclear Regulatory Commission (NRC) spokesperson Neil Sheehan said that Sandy brought a surge of 7.4 feet to Oyster Creek. The plant is obligated to prepare for the consequences of flooding at 8.5 feet, he said, and, at 9.0 or 9.5 feet — Sheehan wasn’t sure — the plant’s pump motors would begin to be flooded.

The storm surge led the plant to declare an “Alert” — the second step in the NRC’s four-tiered emergency action system.

David Tillman, spokesperson for Exelon, the utility company that owns Oyster Creek, would not answer specific questions about the evening Sandy hit the plant (such as the height to which the water level rose, the height of the pump motors, or the actions taken by the plant in response to the alert).  Characteristically for the industry, he insisted that everything worked perfectly and that there were no problems.

The buffer that existed this time may be of little comfort in the future. For all the damage it caused, Sandy was only a Category 1 hurricane — Hurricane Katrina, by comparison, was a Category 3.  Given the challenges even Sandy brought to the Northeast’s nuclear power plants, Remapping Debate decided to investigate the extent to which these facilities are prepared to deal with the flood risks widely expected to increase as a result of global warming.

What would be the consequences were a nuclear power plant to flood?

To grasp what a flood at a coastal nuclear power plant such as Oyster Creek would mean, Dave Lochbaum, director of the Nuclear Safety Project at the Union for Concerned Scientists, told Remapping Debate it is worth reflecting on Japan’s Fukushima Dai-Ichi nuclear power plant disaster in 2011. First, the plant — which ran on General Electric Mark I reactors, the same design as at Oyster Creek and 22 other nuclear plants in the U.S. — lost outside power due to the earthquake. Its backup generators switched on, and “the plant weathered [the earthquake] pretty well,” Lochbaum said. But then the floodwaters arrived, exceeding the facility’s sea wall. “That plant wasn’t unaware of the flooding potential, but the magnitude of the challenge they faced was just more than they could handle,” he said. Because the backup generators and pumps were flooded, there was no means by which to keep the reactors and spent fuel pools cooled.

Once that happens, explained Michael J. Reilly, director of the Division of Planning and Response at the National Center for Disaster Preparedness at Columbia University, “it’s just a matter of time before the heat and the pressure build up and then you have a reactor accident.”

In the worst-case scenario, overheating in the reactor can trigger a hydrogen explosion, which can in turn lead to a breach of the containment structure, the reinforced building in which the reactor core is housed. This would lead to an uncontrolled release of radiation into the atmosphere.

Without an adequate flow of coolant to the spent fuel pool, the heat from the rods would begin to boil the water that remained, which would then evaporate, leaving the rods exposed to the air. At that point, the spent fuel could catch fire and explode, also leading to an unchecked release of radioactive material.

These explosions and fires can damage containment structures, as occurred at the Fukushima Dai-Ichi plant, with some of its buildings reduced to shattered cement and twisted rebar. Ultimately, all of its six reactors were damaged, and three reactor cores melted down, dumping a massive amount of radioactivity into both the water and air. This release led to significant food-chain contamination and the evacuation of 70,000 people. Among the contaminants emitted from the plant was Cesium-137, a radioactive isotope with a long half-life that continues to be found in fish as far away as California.

In the case of a natural disaster like a hurricane, the direct impact on a single nuclear power station would likely be exacerbated by a cascade of indirect effects: a range of emergencies and failures unfolding throughout the surrounding area. As during Sandy, transportation would be radically curtailed with roads, bridges, tunnels, trains, and airports shut, as well as some roads blocked by floodwaters, felled trees, and large-scale debris. There could also be widespread power and water outages, fuel shortages, and downed communication lines.

The indirect effects would likely impair the response to a nuclear power plant disaster. When Hurricane Sandy hit, for example, almost a third of the sirens surrounding Pennsylvania’s Peach Bottom Generating Station near Chesapeake Bay that would warn residents within 10 miles of an emergency were inoperable. The NRC-required backup plan for this situation is for first responders to drive around the area with a loudspeaker announcing the emergency. When Remapping Debate asked the NRC’s Sheehan how this would happen if roads were flooded and blocked, he said the plant could send out text messages and announcements on television. What if there was no power and cell reception was down? “That’s always a concern,” he said.