1. MFW Pump Discharge Check Valve OE Follow Up Dominion North Anna Power Station Gary W. Liffick FW System Engineer FSRUG, Feb 21-24, 2011

2.  Application Overview  Background of OE31369 (update of OE29594)  Corrective Action  Current Status Outline North Anna Power Station: MFW Pump Discharge Check Valve

3. Application Overview  PWR, 963 MWe, Westinghouse NSSS Operational Since: −June 1978 Unit 1 −Dec 1980 Unit 2  Application is Main Feedwater Pump Discharge –3 Pump Circuit, 2 Active, 1 Standby  NozzleCheck Replaced the Tilting Disk Check –October 2007 at 1-FW-19  Feedwater Normal Conditions: –390 F, 1,180 psi, 15,000 GPM per Feedwater Pump  Enertech Supplied: –type DRV-B,18”-900#, RF Flanges, Commercial Grade North Anna Power Station: MFW Pump Discharge Check Valve

4. Application Overview Enertech Supplied Type DRV-B:  18”-900#  RF Flanges  Commercial Grade  WC6 body  ASTM A351 CF8M Diffuser and Disk  Inconel X-750 Spring North Anna Power Station: MFW Pump Discharge Check Valve

5. OE31369, MFW Pump Discharge check valve failed to fully close. Original OE29594.  During March 2009 Outage, backflow detected through check valve.  Disassembly showed 1 broken spring and 2 with visible wear of spring coils due to friction.  Remaining Components indicate normal wear.  Factory installed new springs, radial guide assembly, performed seat leak test.  Returned to site as spare North Anna Power Station: MFW Pump Discharge Check Valve

6. Corrective Action  Increased clearance of spring holder and spring cavity.  Eliminate possible solid height of spring  No change to spring design  Improve check valve reliability without changing Vmin or disk closure force with zero flow North Anna Power Station: MFW Pump Discharge Check Valve

7. NozzleCheck Valve, Type DRV-B 18”-900# RF North Anna Power Station: MFW Pump Discharge Check Valve

8. DRV-B Cutaway North Anna Power Station: MFW Pump Discharge Check Valve

9. NozzleCheck Valve, Animation, Type DRV-B 18”-900# RF North Anna Power Station: MFW Pump Discharge Check Valve

10. Spring Holder and Spring

11. Spring holder wear Spring coil wear Spring Holder and Spring North Anna Power Station: MFW Pump Discharge Check Valve

12. Spring coil wear Spring Holder and Spring North Anna Power Station: MFW Pump Discharge Check Valve

13.  Valves incorporating design changes were installed in all six check valve locations (3 per unit) during 2010  Two valves removed for modification & refurbishment Sept. 2010  Factory evaluation shows spring wear after 12 months and 18 months of service  Valves with the modification are operating per design Current Status North Anna Power Station: MFW Pump Discharge Check Valve

14. Conclusion  Final conclusion is pending the removal of the check valves from service to confirm spring wear has been eliminated  Current PM frequency is 4.5 years  Next valve scheduled for removal/PM is during Spring 2012 Status as of Jan 2011 North Anna Power Station: MFW Pump Discharge Check Valve

15. Gary W. Liffick, FW System Engineer Dominion – North Anna Power Station PH 540 894-2429 Gary.Liffick@dom.com Questions? North Anna Power Station: MFW Pump Discharge Check Valve