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| Entered date | Event description | |
|---|---|---|
| ENS 52476 | 6 January 2017 12:20:00 | During 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 49209 | 22 July 2013 09:55:00 | As a result of an extent of condition review for potential programmatic breakdown issues in response to an apparent violation 05000391/2013611-02 related to TVA's Commercial Grade Dedication Program. TVA has identified a previous Problem Evaluation Reports (PERS) that constitute significant breakdown in a portion of the Quality Assurance program. This review was initiated upon discovery of a misinterpretation of 10 CFR 50.55(e) where it was thought that to be reportable a 'significant breakdown in a portion of the Quality Assurance program' had to be associated with a confirmed substantial safety hazard. The subject of the previous PER is as follows; On May 31, 2011, TVA identified a number of revised Drawing Revision Authorizations (DRAs) that had not been incorporated into work orders to ensure field work required by the DRA revision was implemented in the field. This condition was documented as PER 378571. TVA has concluded that a significant breakdown in a portion of the Quality Assurance program had occurred that could have produced a defect in a basic component. However, TVA has subsequently determined that no safety significance can be attributed to this condition. This issue has been resolved and PER 378571 was closed on February 19, 2013. These items are being reported in accordance with 10 CFR 50.55(e) as significant breakdown in a portion of the Quality Assurance program. The licensee has notified the NRC Resident Inspector. |
| ENS 48871 | 1 April 2013 09:52:00 | WBN (Watts Bar Nuclear) Unit 2 (under construction) determined that a portion of a number of instrumentation lines within multiple systems may have not been inspected completely for proper slope. This condition may have resulted in sense lines being installed with less than the 1/4" per foot minimum slope. No confirmed examples have been identified that would have created a substantial safety hazard at this time. However, walkdowns and evaluations are still underway to confirm that no substantial safety hazards exist. If any examples are found, they will be corrected prior to system turnover to Plant Operations. Therefore, at this time, the safety significance remains indeterminate. This issue has been documented in TVA's corrective action program as Problem Evaluation Report 680826 and is being conservatively reported as a programmatic breakdown by WBN Unit 2 under 10 CFR 50.55(e). The licensee has notified the NRC Resident Inspector. |