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 Entered dateSiteRegionReactor typeEvent description
ENS 524766 January 2017 12:20:00BellefonteNRC Region 2B&W-R-LPDuring a routine inspection on December 6, 2016, Tennessee Valley Authority (TVA) found the Unit 2 Reactor Building Containment Vertical Tendon V281 rock anchor/tendon anchor coupling had failed. The anchor coupling appears to have sheared in the threaded portion allowing the anchor head for the vertical tendon and the anchor head for the rock anchor tendon to separate. TVA had inspected the failed tendon coupling on October 19, 2016, and identified no signs of component specific damage or improper installation creating the potential for an unknown common mode failure. Cause of Deficiency: At this time, the cause for the failure of the V281 rock anchor/tendon anchor coupling is unknown. Safety Significance: As noted previously, the cause for the failure of the V281 rock anchor/tendon anchor coupling is unknown. As a result, the extent of condition can not be determined at this time. If multiple containment tendons are found to be losing the capability to carry tendon design force, and this condition was left uncorrected, it could reduce the capability of the containment structure to perform its design function. TVA had previously completed an analysis of containment structure integrity considering a single tendon coupler failure as a result of a similar failure of a Unit 1 Reactor Building Containment Vertical Tendon V9 in 2009 and determined that the containment structure is maintaining its design capability. Interim Action: Upon discovery on December 6, 2016, the following actions were taken by BLN (Bellefonte) personnel: Access to the Unit 2 tendon gallery was restricted. The area of the V281 tendon failure was subsequently cleaned. Grease samples were obtained and sent to TVA Central Labs for analysis. The couplings from both the rock anchor and tendon anchor locations were removed and sent to TVA Central Labs for metallurgical analysis. Grease samples were also collected from adjacent tendons (V272 through V290) to evaluate if conditions are similar to tendon V281 samples. The failure was entered into the BLN Corrective Action Program (Condition Report 1239343). Update Schedule: TVA plans to provide an update to this report by May 25, 2017 following the completion of the metallurgical and grease analysis. The Licensee has notified the NRC Construction Inspector (Baptist).
ENS 4555910 December 2009 16:23:00BellefonteNRC Region 2B&W-R-LPInspection of failed Unit 1 Reactor Building Containment Vertical Tendon V9 coupling indicates a potential for an unknown common mode failure mechanism for BLN Containment vertical tendon rock anchor couplings. Unit 1 Reactor Building Containment Vertical Tendon V9 experienced a failure of the rock anchor/tendon anchor coupling on August 17, 2009 at approximately 1400 CDT. The time of failure was identified based on a loud noise bang reported by several individuals. Initial investigation failed to reveal the source of the noise. The failed tendon was discovered on August 24, 2009 during a tour of U1 Tendon Gallery, elevation 607. Unsafe conditions previously precluded an inspection of the failed coupling for proper installation or component specific damage. The failed tendon coupling was inspected on 11/23/2009 and showed no signs of component specific damage or improper installation creating the potential for an unknown common mode failure. Safety significance: Until the mechanism of failure is identified the extent of condition will not be known. If multiple containment tendons are found to be losing the capability to carry tendon design force and this condition was left uncorrected, this could jeopardize the ability of the containment structure to perform its design function. Causes of deficiency: The cause of this deficiency is unknown at this time. Further analysis is in progress and when completed, an update to this report will be provided. Interim progress: Grease from the lower anchor head can has been analyzed for moisture content. Results were within vendor specifications. Additional samples have been sent for further analysis as described in Regulatory Guide 1.25 'In-service Inspection of Ungrouted Tendon in Prestressed Concrete Containments.' After successful safe securing of the tendon load, the failed coupling was visually inspected. The visual inspection of the failed coupling did not indicate a component-specific failure mechanism or indication of visually apparent common mode failure mechanism. Based on this inspection visual inspection of additional tendon coupling tendon couplers is not warranted at this time. The coupling has been removed from both the tendon anchorhead and the rock anchor tendon anchorhead and sent to the TVA Central Lab for metallurgical analysis. Records are being reviewed to identify previous non-conformance reports and certificates of compliances for the coupler. An extent of condition and extent of cause investigation will apply to vertical tendons are similar in design, these tendons do not utilize an anchorhead coupler in the design. However, these tendons will be considered in the analysis. Future updates: TVA plans to provide an update to this report by March 31, 2010 following the completion of the metallurgical analysis.
ENS 4506614 May 2009 11:45:00BellefonteNRC Region 2B&W-R-LPDESCRIPTION OF DEFICIENCY Configuration control was not maintained and physical equipment issues were not documented under a Quality Assurance Plan for the period of time from in which Construction Permits CPPR-122 and CPPR-123 were withdrawn until they were reinstated. SAFETY IMPLICATIONS There are no safety implications because controls are in place under TVA's corrective action program that will prohibit current plant structures, systems or components, including those affected in the course of resource recovery activities, from being placed into service without being further evaluated and having been fully restored or replaced. This deficiency has been entered into TVA's Corrective Action Program as Problem Evaluation Report 170988.