Summer is here. Can San Onofre Nuclear Plants Produce Enough Power?


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San Onofre Nuclear Generating Station: Image by awnisALAN

With the San Onofre Nuclear Generating Station shut down due to excessive and inexplicable tube wear, will SCE be able to produce enough electricity to keep Southern California cool this summer?

San Onofre Nuclear Generating Station, operated by Southern California Edison Company (SCE), has three reactors; Unit 1, which was decommissioned in 1992, and San Onofre Units 2 and 3, which are twin Combustion Engineering Pressurized Water Reactor (CEPWR) reactors. Unit 3 was shut down on January 31, 2012, after a tube leak in a steam generator was identified. San Onofre Unit 2 was taken offline earlier that month for routine maintenance and refuelling. But, with unusual wear of the steam generator tubing in both plants, it will be a while before they start up again – which may impact Southern California’s residents this summer.

San Onofre Nuclear Generating Station (SONGS)

San Onofre Nuclear Generating Station, known by the acronym SONGS, is located outside the city of San Clemente, California, on a beautiful stretch of beach sandwiched between Highway 5 and the ocean. Let’s take a drive south, past the two units off of Highway 5. Turn your eyes right and see two large domes standing 160 feet high – each is constructed of 4-foot thick concrete called the containment.

San Clemente, California, location of the San Onofro Nuclear Facility: Image by Lordkinbote

Affectionately nicknamed Dolly Parton, the domes are impressive, and just one of the safety barriers against radiation release in the event of an accident.

The reactor vessels and steam generators are housed in the containment building. The reactor vessels are 8” thick steel structures where the fission of nuclear material occurs. In a typical PWR, (Pressurized Water Reactor) there is a chain reaction of events that results in electrical power:

  1. The core inside the reactor vessel generates heat.
  2. The increased temperature generated by the core heats the pressurized water in the primary loop and carries it to the steam generator.
  3. Inside the steam generator, the pressurized water is passed by tubes, which heats the water on the other side to boiling.
  4. The boiling water creates the steam which drives the turbine generator.
  5. The turbine generator produces electricity.

The plant has two closed loop water systems, so radioactive water from the reactor vessel never enters the turbine generator. Steam generator tubes are a barrier to radioactive steam release and for this reason, integrity becomes important.  SONGS 3 steam generators contain about 10,000 heat transfer tubes, and are among the world’s largest, measuring 20 meters in length, seven meters in diameter and weighing about 580 tons.

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