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Part 1 of 2 Parts
       I have written about the San Onofre Nuclear Generating Station near San Diego, California on a number of occasions. The plant had to be shut down permanently after new steam generators were installed that caused vibrations which cracked pipes. There has been a lot of confusion and court battlers over who was responsible for the problem with the steam generators.
       Now that the plant is shut down, the spent nuclear fuel must be disposed of. This has triggered a new set of arguments and lawsuits over whether the spent nuclear fuel should be stored in dry casks near the plant or trucked somewhere else in the U.S. for disposal.
       In view of the serious earthquakes in Southern California last week, a new question has arisen with respect to the shuttered San Onofre nuclear power plant. What would happen to the plant if there was powerful earthquake in the vicinity of the plant. The impact of such a quake would depend on exactly where the epicenter of the quake was located, how deep the quake was and how much shaking the plant experienced.
      Even the worst imaginable quake would not be able to cause a meltdown because the reactors have been shut down and the nuclear fuel removed. The danger lies in the fate of the three million six hundred thousand pounds of highly radioactive spent nuclear fuel. Currently, most of the spent nuclear fuel at San Onofre is cooling in the spent fuel cooling pools near the reactors. The spent fuel pools are much more vulnerable to the elements than the dry casks to which the spent nuclear fuel is being transferred. It is probable that after the spent nuclear fuel has all been moved into the dry casks, it will stay there for decades until a geological storage facility for spent nuclear fuel can be sited and constructed in the U.S. The earliest that such a new repository could be available is estimated to be 2050.
       While the spent fuel cooling pools require electricity and a flow of water to keep the spent nuclear fuel cool, the dry casks do not. Power outages caused by earthquakes and other natural disaster, accidents or sabotage could endanger the function of the cooling pools. Such power outages pose no threat to the dry casks which are referred to as passive storage systems.
       The San Onofre dry storage system uses huge slabs of concrete which are designed to be able to withstand twice the shaking as the designs for the cooling pools and the reactors. In the dry cask storage system, spent nuclear fuel and other radioactive wastes are placed in steel cylinders encased in concrete. These casks are provided by Holtec International and Areva. There are arguments over how thick the sides of the steel cylinders should be, but everyone agrees that Southern California will be much safer when the spent nuclear fuel has all be transferred to the dry casks.
       Edwin Lyman is acting director of the Nuclear Safety Project with the nonpartisan and nonprofit Union of Concerned Scientists in Washington, D.C. He said, “I am more worried about the spent fuel left in the pools at San Onofre than about the fuel that has been transferred to dry casks. If a large earthquake tore the liner of a pool, causing a rapid loss of cooling water, there is a risk of a spent fuel pool fire that could cause a large dispersal of radioactive material. Although the risk decreases as the spent fuel cools and the pools empty out, it does not go to zero as long as there is fuel in the pools.”
Please read Part 2