USA • NUCLEAR A Nuclear Regulatory Commission special inspection team has been sent to the Three Mile Island nuclear power plant to review the circumstances surrounding the separation of a steam generator tube. The NRC team will evaluate the separation, review the company’s root cause determinations and corrective actions, and perform an independent risk assessment. The plant is operated by Amergen Energy Company.
During an in-service inspection in October of the steam generator tubes, as part of a refuelling outage, Amergen found that a plugged tube had separated from the tube-sheet and caused wear on several adjoining tubes. During the prior period of operation, there was no indication of a problem. The cause of the separation is still being evaluated.
In accordance with NRC requirements, tubes with flaws or degradation above specified limits are plugged (taken out of service by plugging both ends of the tube) or repaired. NRC inspectors will issue an inspection report and ensure corrective action is taken before the plant restarts.
As a separate matter, NRC inspectors are also reviewing Amergen’s work to identify and repair small cracks associated with control rod drive mechanism nozzle penetrations in TMI’s reactor vessel head. CRDM cracks have occurred at other Babcock & Wilcox plants.
