One of the most frightening dangers that nuclear reactors face is the possibility of a nearby earthquake. Containment domes could crack, reactor cores could be severely damaged and melt down, spent fuel pools could be emptied and expose fuel rods to the open air, etc. The ability of the design of a particular reactor to withstand possible earthquakes in the vicinity is very important with respect to licensing the site of a nuclear reactor.
When the Diablo Canyon nuclear power plant was built in San Luis Obispo County, California, the design had to be modified to take into account four faults in the area. The plant was hardened so that it would be able to withstand a 6.75 magnitude quake. In 2008, Pacific Gas & Electric documented the existence of another fault just offshore from the power plant. There were calls for upgrading the plant to be able to withstand a 7.5 magnitude quake but PG&E said that they felt that the plant was safe enough for the time being. A study by the NRC published in 2010 placed the annual probability of a quake strong enough to damage the Diablo Canyon reactors cores was about one in twenty four thousand.
In March of 2011, an offshore quake near Fukushima, Japan destroyed the Fukushima nuclear power plant, causing three of the six reactors to experience a core meltdown. Following the Fukushima disaster, the U.S. Nuclear Regulatory Commission (NRC) issued a report that recommended that the ability of the reactors in the U.S. to withstand a quake and/or tsunami be studied and that vulnerable reactors be strengthened where necessary.
As of 2014, the NRC is assuming that U.S. reactors do not pose any immediate risk with respect to possible earthquakes. There have been calls for more studies on the earthquake risk of the U.S. reactor fleet but there does not seem to be a push at the NRC for any immediate work to upgrade at-risk reactors to new earthquake resistant standards. Some members of the U.S. Senate are calling for immediate redesign and upgrading of vulnerable reactors.
Recent seismological studies have indicated that the dangers of a major quake that could shake the ground enough to threaten major components of a U.S. nuclear reactor are greater than previously thought at some sites but not as great as previously thought at other sites. One estimate is that about twenty four out of the one hundred U.S. power reactors are at greater risk from earthquakes than previously thought.
Operators of some of the more problematic reactors are resistant to expensive analyzes and new construction work to meet the new standards. They suggest that the risk is not great enough to warrant the cost of rebuilding. They may be right but if they are only wrong once, the results could be catastrophic. With so many reactors in highly populated areas, a major nuclear accident could cost billions of dollars and impact public health and the environment.
clear power is having trouble competing in the energy marketplace due to cheap natural gas and expansion of alternative renewable energy sources. The NRC has rules that say if a operator cannot make a profit on selling nuclear power, they will lose their license. One major accident at a nuclear power plant in the U.S. would result in a public movement to shut all nuclear power reactors. The cost of nuclear power would rise and power plants might lose their licenses. It appears to me that we have a choice of starting to phase out nuclear power now or waiting for a major nuclear accident to trigger an expensive emergency shutdown of many U.S. reactors.
Diablo Canyon Nuclear Power Plant:
