An earthquake measuring 5.9 on the Richter scale just occurred less than a hour ago. Its epicenter was in Mineral, Virginia, approximately 10 miles from two nuclear power reactors at the North Anna site. According to statement by a representative of Dominion Power the two reactors were designed to withstand a 5.9 to 6.1 quake. The Nuclear Regulatory Commission ranked the North Anna Reactors as being seventh in the nation in terms of earthquake risks.
The U.S. Nuclear Regulatory Commission requires control rods to be automatically inserted to halt a reactor, if it is impacted by an earthquake. However, the reactor still has a large amount of decay heat that requires either offsite or back-up diesel generators to prevent a meltdown. This was the problem that led to severe accidents at the Fukushima nuclear site on Japan. It is not clear at this time what damage might have been sustained at the nuclear site.
The North Anna reactors are of the Westinghouse Pressurized Water design and went on line in 1979 and 1980 respectively. Since then the reactors have generated approximately 1,200 metric tons of nuclear spent fuel containing about 228,000 curies of highly radioactive materials — among the largest concentrations of radioactivity in the United States.
Nearly 40 percent of the radioactivity in the North Anna spent fuel pools is cesium-137, a long-lived radioisotope that gives off potentially dangerous penetrating radiation and also accumulates in food over a period of centuries. The North Anna Pools hold about 15-30 times more cesium-137 than was released by the Chernobyl accident in 1986. In 2003, the Institute for Policy Studies helped lead a study warning that drainage of a pool might cause a catastrophic radiation fire, which could render an area uninhabitable greater than that created by the Chernobyl accident.
The spent fuel pools at North Anna contain four to five times more spent fuel than their original designs intended. As in Japan, all U.S. nuclear power plant spent fuel pools do not have steel lined, concrete barriers that cover reactor vessels to prevent the escape of radioactivity. They are not required to have back-up generators to keep used fuel rods cool, if offsite power is lost. Even though they contain these very large amounts of radioactivity, spent reactor fuel pools in the United States are mostly contained in ordinary industrial structures designed to protect them against the elements.