ENS 48940
ENS Event | |
|---|---|
20:00 Apr 17, 2013 | |
| Title | Degraded Condition Due To Suspected Valve Body Leakage |
| Event Description | On April 17, 2013 at 1600 [EDT], while performing a valve inspection/repair of the Unit 2 'A' Reactor Coolant Loop Fill Valve (2- RC-HCV-2556A), the as-found inspection results identified evidence of a suspected flaw causing leakage from the valve body to the threads of a stud housing of the valve. This valve is a 2 [inch] 316 SS [Stainless Steel] cast ASME XI (Class 1) 1500 psi valve body of a globe style design. Due to this design and the installed orientation, the RCS pressure medium fills the upper portion of the valve bonnet where the leak is located during normal plant operations. Therefore, this leakage would be considered pressure boundary leakage. 2-RC-HCV-2556A is currently isolated from the Reactor Vessel and is at atmospheric pressure.
This inspection was performed in response to dry discolored boric acid identified during the normal operating pressure boric acid accumulation inspection procedure during the Spring 2013 Unit 2 refueling outage shutdown. An engineering evaluation of the suspected defect will be performed and corrective actions implemented. This event is reportable in accordance to 10CFR50.72(b)(3)(ii)(A) for, 'Any event or condition that results in the condition of the nuclear power plant, including its principal safety barriers, being seriously degraded'. The licensee notified the NRC Resident Inspector and local County Commissioners.
Event Number 48940 was made on April 17, 2013 in accordance with 10CFR50.72(b)(3)(ii)(A) to document a suspected flaw resulting in RCS pressure boundary leakage on Unit 2 'A' Reactor Coolant Loop Fill Valve (2-RC-HCV-2556A). North Anna Power Station is retracting this notification following completion of a cause analysis and metallurgical examination. The analysis determined that the valve leakage was due to the body-to-bonnet gasket joint. The original valve body was especially susceptible to gasket creep, which lead to a loss of sufficient sealing stress. This resulted in body-to-bonnet leakage, not a through-wall leak. Based on this analysis, the reporting requirements of 10CFR50.72(b)(3)(ii)(A) are not met and this event report is being retracted. The licensee has notified the NRC Resident Inspector. Notified R2DO (Ehrhardt). |
| Where | |
|---|---|
North Anna  Virginia (NRC Region 2) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded | |
| Time - Person (Reporting Time:+3.32 h0.138 days <br />0.0198 weeks <br />0.00455 months <br />) | |
| Opened: | Lee Kelly 23:19 Apr 17, 2013 |
| NRC Officer: | Vince Klco |
| Last Updated: | Jun 12, 2013 |
| 48940 - NRC Website
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WEEKMONTHYEARENS 567742023-10-03T15:54:0003 October 2023 15:54:00
[Table view]10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded Degraded Condition ENS 554572021-09-12T21:28:00012 September 2021 21:28:00 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded Degraded Condition Identified While Unit Shutdown ENS 521372016-07-30T15:52:00030 July 2016 15:52:00 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown, 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded Technical Specification Required Shutdown Due to Unisolable Reactor Coolant System Boundary Leakage ENS 507002014-12-23T03:30:00023 December 2014 03:30:00 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown, 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded Unit 1 Technical Specification Shutdown Due to Rcs Pressure Boundary Leakage ENS 504572014-09-15T13:00:00015 September 2014 13:00:00 10 CFR 20.2201(a)(1)(ii), 10 CFR 74.11(a), 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded Failed Fuel Assembly Identified During Core Off-Load ENS 489402013-04-17T20:00:00017 April 2013 20:00:00 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded Degraded Condition Due to Suspected Valve Body Leakage ENS 477672012-03-24T22:55:00024 March 2012 22:55:00 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded Degradation of Steam Generator Nozzle Weld Areas 2023-10-03T15:54:00 | |