Could Tennesseans be at risk of a disaster like the one currently facing Fukushima Dai-ichi? According to the U.S. Nuclear Regulatory Commission, the fourth-most-likely nuclear power plant to suffer core damage and a subsequent release of radiation is right here in Tennessee.
Surprisingly, nuclear power plants built close to active faults, such as those on the California coastline, have a lower risk of damage from earthquakes, because they were built with major earthquakes in mind. But a number of plants built where the chances of earthquakes were previously thought to be minimal now find themselves atop the NRC's list of the ones to be most concerned about. According to the NRC, every American nuclear plant is designed to withstand the strongest earthquake anticipated in its area. But the caveat is that geologists have been revising their estimates of the dangers of earthquakes in states like Tennessee.
The latest estimates come from maps produced by the U.S. Geological Survey in 2008. Of special note, according to the USGS, are the possibilities of major earthquakes along the New Madrid fault, along offshore faults near Charleston, S.C., and in the mountains of East Tennessee. So it turns out that Tennessee is not as earthquake-immune as previously thought.
The new NRC estimates, published in August 2010, are based on the latest USGS maps. These new estimates take the design standards of each plant into account, along with such things as the type of rock or soil the plant is built on.
According to the NRC, the fourth-most-dangerous power plant in the United States is the TVA-operated Sequoyah facility located at Soddy-Daisy, close to Chattanooga. The new per-year estimate of a catastrophic event is 1 in 19,608. The previous estimate was 1 in 102,041. This yields an increase in perceived risk of 520 percent.
If radiation is released from either of the two Sequoyah reactors, Nashvillians could be at risk, depending on factors such as the strength and direction of prevailing winds at the time of the event.
Please keep in mind that this does not mean that a meltdown is imminent. But it seems that some Tennessee nuclear reactors were designed on what may have been faulty, over-optimistic assumptions. Rather than planning for an absolute worst-case scenario, TVA planned only for a “we don’t think Tennessee is likely to have a major earthquake” scenario. Should we trust the bean counters at TVA, or should we demand an immediate, thorough investigation of the risk to Tennesseans, in light of the latest geologic evidence?