[UPDATED] Unit 1 at the Diablo Canyon nuclear plant has completed a refueling outage, adding badly needed generation capacity in California where both units of the San Onofre Nuclear Generating Station remain offline.The 1,151 megawatt Westinghouse reactor at Diablo Canyon began the planned outage April 23 and returned to full power Friday.In a release, PG&E Chief Nuclear Officer Ed Halpin said, “This is a testament to our employees, as well as the nearly 1,000 contractors who came from all over the country to help complete this important work.”Those workers completed 225,000 hours of inspections, refueling tasks and maintenance. The unit also upgraded to a digital process control system, which PG&E said made the reactor the first in the country to execute a PCS replacement to that extent using in house resources.Both pressurized water reactors at Diablo Canyon were operating at full power Monday, according to the NRC. While unit 1 was offline, unit 2 had to shut down April 26 because of an influx of jellyfish-like animals in its water intake. Together they provide about 10 percent of the state's power generation.California utilities are bracing for peak summer demand as both units of the state's other nuclear plant, San Onofre, remain offline following the discovery of premature tube wear in their steam generators.