Five-week refueling shutdown under way at Diablo Canyon

Diablo Canyon nuclear power plant has begun a five-week refueling shutdown that will include replacement of a major component, a reactor vessel head.

The 70-ton component was delivered to the plant in August. As the name indicates, the vessel head sits atop the reactor and maintains its internal pressure.

An additional 1,000 temporary workers have been hired for the outage.

The event will also include activities typical to any outage. These include replacing a third of the fuel in the reactor and performing some 12,000 maintenance and testing tasks.

The outage affects the Unit 2 reactor. The other reactor’s vessel head will be replaced during an outage next year.

Replacing reactor vessel heads became standard practice at commercial nuclear power plants after corrosion on a vessel head in a reactor at the Davis-Besse power plant in Ohio in 2002 nearly caused a radiation leak. The vessel heads at Diablo Canyon were not corroded.

The vessel head replacements are the latest in a series of major component replacements. During previous outages, all eight of the plant’s steam generators were replaced.

The old vessel heads and steam generators remain radioactive and are stored in a building in a canyon behind the plant.

Reach David Sneed at 781-7930.