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Entered date | Event description | |
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ENS 52630 | 23 March 2017 02:48:00 | On March 23, 2017, at 0014 EDT, Watts Bar Nuclear Plant Unit 2 (WBN2) experienced an unplanned trip of both Turbine Driven Main Feed Pumps (TDMFP) following a loss of Main Condenser Vacuum. The trip of both TDMFPs caused an automatic start of both Motor Driven Auxiliary Feed Water Pumps and the Turbine Driven Auxiliary Feed Water Pump. (The) cause of the loss of Main Condenser Vacuum is currently under investigation. The plant was performing a normal startup, and had just synced the main generator to the grid. Subsequent to the event, the plant was transitioned to Mode 3. All rods are fully inserted. Decay heat is being removed via the atmospheric relief valves. Unit 1 remains in Mode 5 for a refueling outage. The licensee has notified the NRC Resident Inspector. |
ENS 50540 | 15 October 2014 22:23:00 | WBN U1 (Watts Bar Nuclear Unit-1) Appendix R (APP R) procedures do not include all the required operator manual actions to ensure manual control of the Unit 1 Turbine Driven Auxiliary Feed (TDAFW) Pump during a fire in room 713-A1A or 737-A1A. The current APP R procedure includes actions to transfer the Unit 1 TDAFW Pump to local control, but does not account for the potential loss of 125 VDC or 120 VAC to the Unit 1 TDAFW pump controls. Without procedural guidance to transfer the 120 VAC and 125 VDC supplies, the operation of the Unit 1 TDAFW pump may not be completed within the required time. Failure to take all the required actions to control the Unit 1 TDAFW Pump places WBN Unit 1 in an unanalyzed condition. WBN has instituted a fire impairment for the affected rooms and established an hourly roving fire watch. The NRC Resident Inspector has been notified of this condition. The affected components are the trip throttle valve and the local control panel. Procedures should be in place by 10/16/2014 to rectify this situation. |
ENS 50245 | 30 June 2014 23:24:00 | On June 27, 2014, TVA identified in a reanalyzed hydrologic analysis for Watts Bar Nuclear Plant (WBN) a deviation from the current hydrologic analysis. The flooding analysis in Section 2.4.3 of the WBN UFSAR assumes that the Watts Bar West Saddle Dike fails completely and instantaneously at approximately 1.5 feet of overtopping during a Peak Maximum Flood (PMF). This assumption exists in the original design basis analysis and the revised analysis which supports WBN-UFSAR-12-01 (Application to Revise Watts Bar Nuclear Plant Unit 1 Updated Final Safety Analysis Report Regarding Changes to Hydrologic Analysis). The results of recent studies of the West Saddle Dike, conducted as part of the Fukushima Order 2.1 flooding review, indicate that the complete and instantaneous failure of the Watts Bar West Saddle Dike may not be a valid assumption. If the dike does not fail, analyses performed using the codes and methods consistent with those used in original plant design show that the east floodwall of the Watts Bar Dam would overtop. As a result of this overtopping, the east floodwall is assumed to fail. Based on this assumption and analysis, failure of the east floodwall of the Watts Bar Dam would result in an increase in the flood level at the WBN Plant Site. The current licensing basis PMF level for WBN is 734.9 feet as stated in Section 2.4.3.5 of the WBN UFSAR. In addition, it should be noted that by letter dated July 19, 2012, TVA proposed a revised PMF level of 739.2 feet. Introducing non failure of the Watts Bar West Saddle Dike indicated a potential increase of approximately 1.7 feet over the revised PMF level. TVA performed additional analysis using current industry standard for flooding analysis. Specifically, TVA modeled the condition using the United States Army Corps of Engineers Hydrologic Engineering Center River Analysis System (HEC-RAS) tool. TVA's analysis of the condition using HEC-RAS determined that all required safety equipment for WBN would not be impacted and are considered operable based on a Prompt Determination of Operability completed on June 30, 2014. This report addresses a condition as described in 10 CFR 50.72 (b)(3)(ii)(B). TVA is making this report consistent with the guidance of NUREG-1022 regarding the application of engineering judgment to the evaluation of reportability of an unanalyzed condition. The NRC Resident Inspector has been notified of this condition.
On June 30, 2014, TVA reported (Event 50245) that during a re-analysis conducted as part of the Fukushima Order 2.1 flooding review, a probable maximum flood (PMF) design assumption that the Watts Bar Dam west saddle dike fails completely and instantaneously at approximately 1.5 feet of overtopping, was determined to be a non-conservative flood model assumption (i.e., invalid). As a result, TVA postulated that Watts Bar Dam's east floodwall would fail, increasing the site flood level at Watts Bar Nuclear Plant (WBN) by 1.7 feet; a condition that was beyond the current licensing basis. Through subsequent analysis, TVA has demonstrated that although the west saddle dike may not completely and instantaneously fail during a PMF (as previously assumed), the consequential increase in reservoir levels does not result in a failure of the Watts Bar Dam east floodwall and would not result in an increase in the flood level at WBN. Therefore, the previously reported 10 CFR 50.72(b)(3)(ii)(B) event is being retracted. The NRC resident Inspector has been informed of this event retraction. Notified the R2DO (Hickey). |
ENS 49818 | 11 February 2014 19:28:00 | Preliminary Westinghouse transient analysis calculations of Watts Bar Nuclear (WBN) Unit 1 fire protection features revealed that there is less time than previously credited to perform certain operator manual actions (OMA) to prevent Pressurizer (PZR) overfill during an Appendix R fire. Specifically, an assumed Appendix R fire in rooms 713.0-A28, 737.0-A1A, 757.0-A2, 757.0-A5, 757.0-A9, 772.0-A1, 772.0-A2, or 772.0-A5 could result in spurious operation of multiple components in the normal and emergency charging flow paths. Westinghouse's analysis indicates the required time to isolate the normal charging path is approximately two minutes, securing the second charging pump is approximately four minutes and isolating the emergency charging path is approximately 12.5 minutes. Based on this preliminary analysis, WBN procedures are non-conservative since they require these actions to be completed in 18 minutes. TVA has verified that potentially impacted Appendix R equipment remains functional; however, a compensatory fire watch has been established for the above listed areas. This immediate action will ensure that the approved Appendix R Fire Safe Shutdown Plan can be achieved. The licensee has notified the NRC Resident Inspector. |
ENS 49730 | 15 January 2014 17:18:00 | A contract supervisor had a confirmed positive for alcohol during a random fitness-for-duty test. The employee's access to the plant has been suspended. The licensee has notified the NRC Resident Inspectors. |
ENS 48950 | 21 April 2013 02:29:00 | An unidentified individual fired a shot at a site security vehicle. "Watts Bar Nuclear Plant Declared a Notice of Unusual Event (NOUE) at 0211 EDT April 21, 2013. (The licensee notified) Rhea and Meigs County Sheriff departments for on-site support. A notification of the event discussed above was made to the State of Tennessee. A notification of the event discussed above was made (to the) U.S. Department of Energy (DOE) Electricity Delivery and Energy Reliability." The licensee notified the NRC Resident Inspector. Notified DHS, FEMA, USDA, HHS, DOE, NICC, EPA, FBI SIOC and Nuclear SSA via email. * * * UPDATE FROM DAMON FEGLEY TO PETE SNYDER AT 0634 EDT ON 4/21/13 * * * This information is being provided to the NRC for a 10CFR50.72(b)(2)(xi) notification. TVA is planning on making a news release to local media affiliates and posting the news release on TVA's website. This news release is in reference to the Notification of Unusual Event (NOUE) Watts Bar Nuclear Plant recently entered for a security condition. Notified R2DO (Vias).
(At) 1230 EDT Watts Bar Nuclear plant terminated the Notification of Unusual Event. TVA is planning on making an additional news release to local media affiliates and posting the news release on TVA's website. This news release is in reference to the Notification of Unusual Event (NOUE) Watts Bar Nuclear Plant recently terminated. The licensee notified the NRC Senior Resident Inspector. Notified the R2 IRC, IRD (Grant), NSIR (Wiggins), NRR (Uhle), ILTAB (Johnson), DHS, FEMA, USDA, HHS, DOE, NICC, EPA, FBI SIOC and Nuclear SSA via email. |