U.S. Nuclear Power Plants: Vulnerable To Earthquakes?

 NRC Affirms Safety, But Watchdog Raises Concerns

Dan Shapley / News Editor

The 6.3-magnitude earthquake that shook the largest power plant in the world to its knees this week in Japan has raised the specter of a similar natural disaster affecting plants elsewhere in the world, including in the United States.

The earthquake caused a fire in a transistor, led to the leak of water with low radioactivity, and prompted the automatic shutdown of the Tokyo Electric Power Co. reactors.

Both the Nuclear Regulator Commission and the nation’s leading nuclear energy watchdog, the Union Of Concerned Scientists, agree that U.S. plants are built to withstand earthquakes.

But the watchdog sees vulnerabilities that the federal agency doesn’t acknowledge.

“The good news about our plants is we knew about earthquakes before, and as a result of that, the plants in California, for example, are more robust and built for a stronger shake than plants on the East Coast for obvious reasons,” said David Lochbaum, director of UCS Nuclear Safety Project.

The bad news, Lochbaum said, is that Japan knew about earthquakes too, and designed its reactors to meet standards that are as stringent, if not more stringent than those used in the most earthquake-prone parts of the country, like California.

And while critical reactor features are built to withstand earthquakes, secondary infrastructure like piping and electrical equipment could fail, Lochbaum said, potentially leading to a meltdown if backup safety features fail.

“Much of the rest of the plant — electrical equipment, fire sprinklers, transformers, hydrogen used to cool generators and turbines, piping,” he said, “much of that is not built to the same high standards, and as a result … that’s what fails first,”

To avoid meltdowns or other dangerous accidents, all 104 U.S. reactors were built to automatically shut down if an earthquake of a certain magnitude strikes. The degree of protection was determined on a plant-by-plant basis, depending on past seismic activity, said Scott Burnell, spokesman for the NRC. To build a plant, companies must first study the area and determine the strongest earthquakes that have occurred there in the past 10,000 years.

“All of this information is used to determine what we would call the ’safe shutdown earthquake’ for the site. That definition is exactly what it sounds like — the strength of earthquake that a plant would have to withstand and safely shutdown afterwards and remain safely shutdown,” Burnell said. “So that would mean not only would you need to cut off the reaction, but also various pumps and storage tanks to cool reactor after you have shut down the reaction.”

Burnell rejected Lochbaum’s assertion that secondary equipment could lead to a meltdown or other larger problem. All systems necessary to safely shut down a plant must be built to withstand an earthquake of the designated size, he said.

“The basic dividing line is between systems that will support safe shutdown of the plant and everything else,” Burnell said.

That said, if the experience in Japan teaches Japanese regulators anything new that should be applied to U.S. reactors, international agreements facilitate the sharing of that kind of technical and operational information, Burnell said.

Lochbaum said that is critical. And while he raised concerns about earthquake preparedness, he said it was low on the list of concerns about nuclear power, relative to more common if mundane issues like the slow degradation of equipment resulting from maintenance projects being deferred.

With most power plants in the country licensed to run for about another two decades, and with the first proposals to build anew being put forward in a generation, he said now is the time to plan for the next generation of plants.

“That gives us time to get it right, or as close to right as we can,” Lochbaum said. “9/11 has happened. We need to make future designs more secure, and we need to make them less vulnerable to efforts by bad guys. Likewise we need to look how to make them as safe as we can.”