ENS 48795
ENS Event | |
|---|---|
16:55 Feb 28, 2013 | |
| Title | Closed Cooling Water Isolation Valve Fails Local Leak Rate Test |
| Event Description | On February 28, 2013, at 1155 EST, with the unit in Refueling Mode, a determination was made that reactor building closed cooling water (RBCCW) isolation valve (2P42-F051) exceeded its acceptance criteria for designed leakage when performing local leak rate testing. Diagnostic testing confirmed that all the leakage from its test boundary is going through this valve with an 'as found' leakage of >200,000 sccm at 32.87 psig. This valve is the outboard isolation barrier for that affected primary containment penetration with the inboard barrier being the RBCCW system itself as a 'closed' system.
Previous practice is to conservatively include any leakage through this valve when performing as found leak rate tests as part of the primary containment leakage summary or as part of 0.6La. This is considered conservative since the RBCCW system inside containment is assumed to remain intact following a design basis accident (DBA) loss of coolant accident (LOCA). If the closed system remains intact there is no path for leakage to exit primary containment through this system. Since the past practice is to include the 'as found' leakage through this valve as part of 0.6La and since the 'as found' leakage would result in exceeding La, this condition is being considered a condition that results in the principal safety barriers being seriously degraded. This leakage would represent a loss of the containment function since the leak rate exceeded the Technical Specification limiting condition for operation (LCO) for primary containment. Further investigation is underway to determine if leakage through this single containment barrier is required to be included in the Appendix J primary containment leakage summary, since it is associated with a closed system. The licensee notified the NRC Resident Inspector.
Further investigation revealed an Appendix J exemption that was granted for the Hatch Unit 2 local leak rate test (LLRT) program in the 1978 time frame that specifically addressed the primary containment penetration that has primary containment isolation valve (PCIV) 2P42-F051 as its outboard barrier and the 'closed' system as its inboard barrier. The exemption recognizes that this system is designed to be intact and water filled post-LOCA, allows testing of the of the PCIV with water and states that the leakage through this PCIV is not included in the 0.6 La total. Since the Hatch RBCCW system supplying components inside primary containment is a 'closed' system and remains intact and water filled post-LOCA, there is no leakage path from primary containment through this RBCCW penetration. Since no leakage from primary containment can occur through this penetration in its 'as found' state, this condition does not represent a condition that seriously degrades a principal safety barrier. As such this condition has been determined to no longer meet reporting requirement 10CFR50.72(b)(3) and is therefore not reportable. Based on this information the previous notification is being retracted. The licensee notified the NRC Resident Inspector. Notified R2DO (O'Donohue). |
| Where | |
|---|---|
Hatch  Georgia (NRC Region 2) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded | |
| Time - Person (Reporting Time:+0.3 h0.0125 days <br />0.00179 weeks <br />4.1094e-4 months <br />) | |
| Opened: | James Anderson 17:13 Feb 28, 2013 |
| NRC Officer: | Pete Snyder |
| Last Updated: | Mar 15, 2013 |
| 48795 - NRC Website | |
WEEKMONTHYEARENS 569592024-02-11T15:11:00011 February 2024 15:11:00
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