NRC Agrees Modifications to South Carolina Nuclear Plant Adequate If Dam Fails
NRC said the flood modifications included building new or enhanced flood walls and other features, as well as moving some power lines and equipment to locations less prone to flooding. Duke Energy informed the agency two months ago that those modifications were complete, and a subsequent inspection caused NRC to determine that the company has satisfied the commitments in the 2010 confirmatory action letter.
The Nuclear Regulatory Commission announced June 17 that it has found the modifications completed by Duke Energy at its Oconee nuclear plant will adequately protect the plant's three reactors from a potential failure of the upstream Jocassee Dam. An NRC staffer wrote a memo within days of the start of the Fukushima Daiichi nuclear power plant crisis saying the dam's failure would be as devastating to the Oconee plant as the tsunami that struck the Japanese plant turned out to be. The Oconee plant is located near Seneca, S.C., about 30 miles west of Greenville. Its three reactors are pressurized water reactors that were licensed to operate in 1973 and 1974 and had their licenses renewed in 2000, according to information available on the NRC website.
In 2008, the NRC staff issued a letter to Duke Energy requesting information related to external flooding, including the potential failure of the dam, which is located about 12 miles upstream from the plant. A detailed flood hazard analysis took two years to complete and in 2010, Duke submitted the analysis and
NRC issued a confirmatory action letter (CAL) documenting the company’s commitments; Duke also implemented some interim compensatory measures that were inspected by NRC in 2010.
The Fukushima Daiichi accident happened in 2011, and NRC issued another letter in 2012 requesting additional information on flooding as the agency worked to ensure lessons learned from Japan's experience were applied to U.S. plants, including Oconee. Duke then submitted its flood hazard reevaluation report in 2013 and a revised flood hazard reevaluation report in 2015. NRC accepted that 2015 report for the purposes of the meeting the CAL and, in addition, NRC inspectors evaluated the Oconee plant's modifications as the company completed each of those steps. NRC said the modifications included building new or enhanced flood walls and other features, as well as moving some power lines and equipment to locations less prone to flooding.
Duke Energy informed the agency two months ago that flooding modifications were complete, and a subsequent inspection caused NRC to determine that the company has satisfied the commitments in the 2010 CAL. "The completion of the commitments in the confirmatory action letter gives the NRC confidence that the Oconee plant is adequately protected from external floods, including scenarios involving the failure of the dam," said NRC Region II Administrator Cathy Haney, who added that the years it took to resolve the flooding issues at Oconee were necessary to ensure the best analyses were used, information from the accident in Japan was incorporated, and plant modifications meet all requirements.