23 May (NucNet): The US Nuclear Regulatory Commission is launching a special inspection at Duke Energy’s Shearon Harris nuclear power plant in North Carolina to assess the circumstances surrounding the discovery of a flaw of about 0.6 centimetres on the plant’s reactor pressure vessel (RPV) head.
The single-unit plant was shut down on 15 May 2013 when further analysis of ultrasonic data gathered during an earlier refuelling outage revealed an irregularity near a nozzle on the RPV head, the NRC said.
The NRC said the flaw did not penetrate the RPV head wall and there was no evidence of leakage. Duke Energy has begun the repair process.
An NRC spokesman said there was no immediate threat to the public or plant workers, but because the discovery is on the RPV head and was not seen in the original review, the commission is sending specialists to evaluate the issue.
The NRC said its resident inspectors at Shearon Harris “immediately began assessing the incident” and are continuing to monitor the plant’s activities. They are being supplemented this week by two specialised inspectors from the NRC’s Region II offices in Atlanta.
The team will, among other things, develop a timeline, review Duke’s actions leading up to the discovery of the flaw, examine the previous ultrasonic testing records for the RPV head, evaluate the company’s repair plans and determine if there are “generic issues that should be communicated to other nuclear plants”.
The on-site portion of the inspection is expected to take about a week and a half. A report documenting the results will be issued within 45 days of the completion of the inspection, the NRC said.
Shearon Harris-1 is a 930-megawatt pressurised water reactor unit that began commercial operation in May 1987. In 2008, the NRC extended the plant’s operating licence until 2046.
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