ML20056G960
| ML20056G960 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 09/01/1993 |
| From: | Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 93-513, NUDOCS 9309080008 | |
| Download: ML20056G960 (5) | |
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YllfGINIA EtecTHIC AND l'OWElf COM1%NY R ICIIM ON D, VIItGINI A Mil 2 (a l September 1,1993 4
U.S. Nuclear Regulatory Commission Serial No.93-513 Attention: Document Control Desk JHURMN R3 Washington, D.C. 20555 Docket Nos.
50-338 50-339 License Nos. NPF-4 NPF-7 Gentlemen:
VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION UNITS 1 & 2 INSPECTION REPORT NOS. 50-338/93-19 AND 50-339/93-19 REPLY TO A NOTICE OF VIOLATION We have reviewed your letter of August 5,1993, which referred to the inspection conducted at North Anna Power Station from June 20,1993 to July 17,1953,and reported in inspection Report Nos. 50-338/93-19 and 50-339/93-19. Our reply to the Notice of Violation is attached.
We are also concerned that corrective actions from a previous similar event, relating to the position of the EDG muffler bypass valve, that was documented in WRC Inspection Report Nos. 50-338/92-03 and 50-339/92-03 did not prevent recurrence.
Subsequently, we changed our operating practice of isolating the EDG muffler bypass line during testing. The EDGs may now be tested with the muffler bypass valves in the i
open poution. Procedures have been revised accordingly. This change in operating practice was documented in our letter dated July 20,1993. Furthermore, the chain operators for each of the EDG muffler bypass valves have been removed and the valves have been locked open to prevent further misalignments.
If you have any further questions, please contact us.
Very truly yours, s
W. L. Stewart Senior Vice President - Nuclear Attachment l
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U.S. Nuclear Regulatory Commission Region il 101 Marietta Street, N.W.
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Atlanta, Georgia 30323 l
NRC Senior Resident inspector North Anna Power Station i
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1 REPLY TO A NOTICE OF VIOLATION INSPECTION REPORT NOS. 50-338/93-19 AND 50-339/93-19 NRC COMMENT During an NRC inspection conducted on June 20, through July 17,1993, a violation of NRC requirements was identified. In accordance with the " General Statement of Policy and Procedure for NRC Enforcement Actions," 10 CFR Part 2, Appendix C, the violation is listed below:
Technical Specification 6.8.1 requires that written procedures be established, implemented and maintained including the applicable procedures recommended in Appendix A of Regulatory Guide 1.33, Revision 2, February t
1978, to include operating procedures.
Operating Procedure 1-OP-6.5A, Revision 13,1H and 1J Emergency Diesel Generator Post-Opc ational Check, Step 5.3.4.e requires the EDG exhaust muffler bypass valve to be opened and locked.
Contrary to the above, operating procedure 1-OP-6.5A was not implemented l
properly in that on June 2,1993, while performing step 5.3.4.e, an operator failed to fully open the EDG exhaust muffler bypass valve prior to locking the valve.
l This is a Severity Level IV violation (Supplement I).
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REPLY TO A NOTICE OF VIOLATION 1.
REASON FOR THE VIOLATION The violation was caused by personnel error resulting in the misalignmcnt of the Emergency Diesel Generator (EDG) oxhaust muffler bypass valve. The misalignment occurred on June 2,1993 fo lowing the performance of Operating Procedure 1-OP-6.5A,1H and 1J Emergency Diesel Generator Post-Operational Check.1-OP-6.5A required the EDG exhaust muffler bypass valve be opened by manipulating the chain operator 1 1/2 ravolutions. A chain operator is required because the valve is in the ventilation penthouse on the EDG roof building and cannot be seen by the operator in the EDG room. A portion of the chain is painted to provide the operator an indication of valve l
chain passing the stanchion at 1/2 revolution and then again when full open at position. The number of revolutions is determined by the painted portion of the 1 1/2 revolutions. The valve is then locked in place. However, the operator positioning the valve on June 2,1993 only revolved the chain 1/2 revolution prior to locking the valve in place. This left the valve approximately 29% open instead of fully open.
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CORRECTIVE STEPS WHICH HAVE BEEN TAKEN AND THE RESULTS ACHIEVED The EDG muffler bypass valve was immediately opened to its full open position.
Independent verification of the local open valve position indicator was performed. The EDG muffler bypass valves for the remaining EDGs were verified by local inoication to be locked in the full open position. Operating Procedure 1-OP-6.5A was revised to require local independent verification of the EDG muffler bypass valve.
Engineering evaluations were performed and it was determined that impact of a tornado missile would develop sufficient loads to separate the expansion joint in the exhaust system and not restrict exhaust flow. Based on these engineering evaluations, the EDG was considered operable.
Engineering evaluations were also performed to determine the probability of a tornado missile striking the exposed portion of the EDG exhaust. As a result,.
the current North Anna design was shown to be overly conservative. The l
evaluation determined the probability of a tornado missile striking the exhaust line and causing a high back pressure that would stop the EDG was less than 10-6 per year. ANSI /ANS 51.1-1983, Nuclear Safety Criteria for the Design of Stationary Pressurized Water Reactor Plants, which was issued subsequent to the licensing of North Anna, in part states that events with' an occurrence frequency of less than 10-6 per year need not be considered for design. Thus, current industry standards show the North Anna design may be overly
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conservative for a tornado missile event.
An evaluation was performed to determine whether it was necessary to test the EDGs with the muffler bypass line isolated. Testing with the EDG muffler i
bypass line isolated was originally performed to reduce noise levels. However,
the results of the evaluation determined that testing with the EDG muffler bypass line isolated was unnecessary. Therefore, we eliminated the practice of isolating the EDG muffler bypass line during testing. The EDGs may now be tested with the muffler bypass valves in the open position. Procedures have been revised to change the operating and testing configuration of the EDGs.
This change in operating practice was documented in our letter dated July 20, 1993. In addition, the chain operators for each of the EDG muffler bypass valves have removed and the valves have been locked open to prevent further misalignmsats.
A Human Performance Enhancement System evaluation on this event was performed.
Recommendations as a result of this evaluation are being implemented, as appropriate.
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CORRECTIVE STEPS WHICH WILL BE TAKEN TO AVOID FURTHER VIOLATIONS No further corrective actions are required.
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THE DATE WHEN FULL COMPLIANCE WILL BE ACHIEVED Full compliance has been achieved.
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