U.S. most vulnerable reactor: Indian Point 3, N.Y.

says the margin of safety has been reduced.

In the thirty-five years since Indian Point 3 got its license to operate in 1976, the same era when most of today’s U.S. nuclear reactors were built, geologists have learned a lot about the dangers of earthquakes in the eastern and central U.S.

New maps drawn by the U.S. Geological Survey in 2008 enabled NRC to update their estimates for earthquake risk based on the proximity, severity, and frequency of earthquakes, as well as the design standards and types of bedrocks into account, reducing areas of negligible risk.

The top 10 nuclear power sites with the highest risk of suffering core damage from an earthquake are listed below, showing their 2008 NRC risk estimates as compared to the 1989 geological data.

1. Indian Point 3, Buchanan, N.Y.: 1 in 10,000 chance each year. Old estimate: 1 in 17,241. Increase in risk: 72 percent.

2. Pilgrim 1, Plymouth, Mass.: 1 in 14,493. Old estimate: 1 in 125,000. Increase in risk: 763 percent.

3. Limerick 1 and 2, Limerick, Pa.: 1 in 18,868. Old estimate: 1 in 45,455. Increase in risk: 141 percent.

4. Sequoyah 1 and 2, Soddy-Daisy, Tenn.: 1 in 19,608. Old estimate: 1 in 102,041. Increase in risk: 420 percent.

5. Beaver Valley 1, Shippingport, Pa.: 1 in 20,833. Old estimate: 1 in 76,923. Increase in risk: 269 percent.

6. Saint Lucie 1 and 2, Jensen Beach, Fla.: 1 in 21,739. Old estimate: N/A.

7. North Anna 1 and 2, Louisa, Va.: 1 in 22,727. Old estimate: 1 in 31,250. Increase in risk: 38 percent.

8. Oconee 1, 2 and 3, Seneca, S.C.: 1 in 23,256. Old estimate: 1 in 100,000. Increase in risk: 330 percent.

9. Diablo Canyon 1 and 2, Avila Beach, Calif.: 1 in 23,810. Old estimate: N/A.

10. Three Mile Island, Middletown, Pa.: 1 in 25,000. Old estimate: 1 in 45,455. Increase in risk: 82 percent.

Northeast of Chattanooga, Tennessee, the Tennessee Valley Authority’s Sequoyah 1 and 2 nuclear plants had been thought to have a risk of core damage from an earthquake happening once every 102,041 years. The new estimate is once every 19,608 years.

The increase in risk is so rapid that an NRC research task force in September sent two recommendations to NRC management which included moving the issue from the research staff to the regulatory staff and from study to action. Secondly, they were to start evaluating which nuclear power plants need a “backfit,” or structural reinforcements.

Another indication