newjerseynewsroom.com

BY ROGER WITHERSPOON

NEWJERSEYNEWSROOM.COM

The Nuclear Regulatory Commission may force the nation’s nuclear power plants to reevaluate their earthquake detection and safety systems and the manner in which they calculate their resistance to earthquakes as a result of unexpected damage to American and foreign reactor complexes caused by recent earthquakes.

The agency has been studying the need to upgrade earthquake protections and evaluations since 2005, in partial recognition of the inadequacy of nuclear plant designs based on the fledgling science of seismology in the 1950s and early 1960s. But the extensive damage to the six-reactor Fukushima Daiichi nuclear complex in Japan, and unexpected damage to the twin North Anna nuclear power plants in Virginia caused by the August 23 earthquake has given new impetus to the NRC’s ongoing work. Though the damage to the North Anna Units 1 & 2, about 40 southeast of Richmond, are considered minor, the plants remain shut pending a special inspection ordered by Victor McCree, director of Region II, which encompasses southern nuclear operations and the construction of any new reactors anywhere in the country.

The decision to send a formal Augmented Inspection Team followed the notification by Dominion Power, which owns and operates the North Anna plants that the ground motion of the Virginia earthquake, measured at 5.8 in magnitude, “may have exceeded the ground motion for which it was designed.”

All of the nation’s nuclear power plants, which were designed in the 1950s and 1960s, were supposed to be able to handle the acceleration of the ground motion and shaking associated with the largest historically recorded earthquake within a 50 mile radius of the site. For North Anna, a ground motion of .12 of normal gravity is the “design basis” incorporated into the plant’s license. That was based on an earthquake of a magnitude 4.8, and the plant was designed to withstand the gravitational tug resulting from an earthquake of 5.1 in magnitude.

McCree said in a statement that “the AIT provides us with the resources needed to completely understand all of the effects at North Anna and gather important information for the NRC’s continuing evaluation of earthquake risk at all U.S. nuclear plants.”

While the major safety and structural systems at North Anna are apparently undamaged, the transformer providing off site power failed, causing an immediate “station blackout” and shutdown. The plant’s diesel generators kept the reactors and spent fuel pools cool until off site power was restored.

“Not only are the operating reactors getting special attention,” said NRC spokesman Roger Hannah, “but we are also looking at the spent fuel pools and the dry cask storage area, where 25 of the 27 casks moved slightly during the earthquake. They weigh 100 tons or so when fully loaded, and it would take significant movement of the earth for them to fall over. But they moved from a half inch to 4.5 inches on their pad.”

It had been thought that the massive concrete and steel dry casks would be impervious to any eastern earthquakes. In this case, said Hannah, none of the casks appear to have been breached.

But on Thursday, the regulatory agency signaled its intention to issue a “generic letter” to all 104 nuclear power plants requesting a new evaluation of the manner in which earthquakes were analyzed and incorporated into their designs, and what steps, if any, may be needed to strengthen the plants and their support systems. A special inspection of all the nation’s nuclear plants after the meltdowns at the Fukushima Daiichi plants this spring discovered that while most plants should be able to withstand known levels of regional earthquakes, their support systems were not protected. In many cases, should an earthquake trigger a fire, the buildings on plant sites housing firefighting equipment, and the water mains from the municipal water systems were not designed to meet any earthquake standards and could be wrecked in a severe earthquake.

In addition, all nuclear plants have miles of underground pipes and conduits – many of these encased in concrete and inaccessible to inspections. Virtually all of the ageing plants have leaked radioactive water into the surrounding environment, primarily through these underground systems, or deteriorated spent fuel pools. New York’s Indian Point plants have continuously leaked into what amounts to a radioactive lake under the plants, about 25 miles north of New York City, which is steadily seeping into the Hudson River.

In New Jersey, the twin Salem nuclear plants in Lower Alloways Creek Township have leaked radioactive water into catch basins flowing into the Delaware River, and the Oyster Creek nuclear power plant, in Lacey Township, is still cleaning up a radioactive leak in 2002 that contaminated Barnegat Bay.