Beaver Valley corrosion prompts calls for increased inspections
Interest groups Citizen Power and Beyond
Nuclear have filed a request with NRC to supplement Beaver Valley’s
safety evaluation report, or SER, to reflect the April 2009 discovery
of corrosion that permeated unit 1’s containment liner.
The groups said in a July 7 letter to NRC that “[t]he only way to determine if corrosion of the liner is a safety issue is to conduct an adequate [ultrasonic test] examination of the containment liner.” Citizen Power had petitioned the agency roughly six weeks earlier, asking the commission to order staff to supplement the Beaver Valley SER.
The interior of the liner was being inspected April 21 during Beaver Valley-1’s refueling outage when “a suspect area” about three inches in diameter was identified, FirstEnergy Nuclear Operating Co. said in an April 24 event report to the NRC (INRC, 11 May, 4). Fenoc later found a rectangular area measuring about one inch by three-eighths of an inch penetrating through the containment steel liner plate, the company said in the report.
Citizen Power stated in its letter that Fenoc should either test 100% of the unit’s containment liner or modify the testing methodology to reflect the existence of corrosion.
The groups said their proposals would go beyond Fenoc’s planned tests, which include ultrasonic testing of the repaired hole and supplemental volumetric examinations of sample locations of the containment liners in both nuclear units. They said standards set out in NRC’s generic aging lessons learned report, or GALL, call for enhanced inspection techniques should significant amounts of corrosion be found. GALL is the agency guidance staff uses to review license renewal applications.
Arnold Gunderson, a nuclear engineer retained by Citizen Power, said in a July 29 interview that the corrosion problem at Beaver Valley-1 raises questions about the safety of aging reactors. The unit’s operating license went into effect in 1976 and runs through 2016. Fenoc in August 2007 applied for a 20-year license renewal for both Beaver Valley units.
But Fenoc spokesman Todd Schneider said in a July 30 email that his company’s testing procedures are “prudent” and provide “reasonable assurance” to the liner’s operability.
Ted Robinson, staff attorney at Citizen Power and cosigner of the letter, said in a July 30 e-mail that he had not yet received a response to the July 7 letter, which was sent NRC’s Advisory Committee on Reactor Safeguards, or ACRS, in Washington. Schneider said company representatives, who met with the ACRS in July, are awaiting the commission’s decision on the group’s request on license renewal.
The liner has been “successfully repaired and tested,” Schneider said. There is no evidence of uniform corrosion in the liner, he said. “A statistical random sampling of the containment liner with ultrasonic testing of the sampled locations will provide reasonable assurance of the overall liner condition,” he said. “Additionally, 100% visual inspections of the accessible liner will be conducted.”
But the groups expressed concern in their letter that visual and integrated leak rate testing would fail to identify major exterior corrosion before a breach in the liner appears. “Therefore, there could be considerable corrosion of the exterior of the liner at this moment,” the letter stated.
The groups are concerned that the corrosion seen at Beaver Valley could point to a wider problem in the nuclear industry. Gundersen, who was an expert witness for Citizen Power’s May 27 petition, said in a May 25 legal declaration that Beaver Valley-1’s sub-atmospheric containment design could be the root cause of the oxygen and moisture buildup behind the liner. In a sub-atmospheric containment system, pressure inside the containment is below the pressure outside containment.
Gundersen called for “prompt” ultrasonic inspections at unit 1. Visual and partial ultrasonic techniques are not enough, he said, adding that the detection of three corrosion sites in 2006 and one in 2009 indicate a “gross breakdown” in quality assurance during unit 1’s construction. “I believe the breach of this containment liner with no prior warning following repeated and various types of containment inspections which occurred for more than 33 years has broad nuclear policy and safety ramifications,” according to his declaration.
Gundersen said in a July 29 interview that if more problems are discovered during ultrasonic testing, NRC should consider testing the entire fleet of sub-atmospheric containment designs.
He said the problem also raises questions about the safety of aging reactors. Beaver Valley-1’s license, which went into effect in 1976, runs through 2016. Fenoc in August 2007 applied for a 20-year license renewal for both Beaver Valley units.
But Fenoc’s Schneider said a root-cause analysis determined that the corrosion at unit 1 was caused by the piece of wood contacting the liner since construction. “This type of foreign material condition (piece of wood touching the liner) has been found at other US nuclear power plants,” Schneider said. “As this condition is not prevalent throughout the liner, a random inspection using statistically based ultrasound test examinations will provide reasonable assurance to overall liner condition.”
Used with permission from The McGraw-Hill Companies, Inc.
Copyright © 2009, The McGraw-Hill Companies