Steve Byrne, S.C. Electric & Gas Company’s chief operating officer, told investors during a recent conference call that four cracked welds were discovered in October when the plant was shut down for refueling.
“An extensive robotic inspection of the reactor vessel showed there was no leakage from these areas as a result of the condition of the welds,” he said. “We notified the Nuclear Regulatory Commission as required and developed a strategy to repair the welds.”
The strategy involves sealing the damaged welds to avoid further “water stress corrosion cracking,” the company told federal regulators in a 24-page action plan. Those repairs, once completed, would allow the unit to operate another 40 years.
The reactor at the Summer plant, about 80 miles northeast of Augusta, is similar in age and design to Plant Vogtle’s two units in Burke County, Ga., although no cracks or related flaws have been discovered at the Georgia site.
“The Vogtle reactors are inspected regularly, as required by the industry,” said Southern Nuclear spokeswoman Michelle Tims.
Unit 1 was most recently examined in September, with no issues found, she said, and Unit 2 – last inspected in 2011 – will be examined again in 2013, she said.
“Differences in design, operating temperatures, manufacturing techniques and plant chemistry can impact the sensitivity of the reactor vessel head for the formation of cracks,” she said. “Southern Nuclear carefully considers these factors at all reactors.”
Although the cracks at the Summer unit were discovered before they could become a safety hazard, the situation illustrates the sort of problems facing an aging fleet of U.S. nuclear plants, said Tom Clements of the Alliance for Nuclear Accountability.
“Summer was licensed in 1982 and Vogtle in 1987 and 1989,” he said. “The age of the Vogtle units necessitates an aggressive aging management program, including thorough inspection of the reactor vessel, especially at penetrations which have welds, for cracking and flaws.”
Both Vogtle and Summer are also sites where nuclear reactors are under construction – the first to be authorized and built in the U.S. in a generation.