ML18153B101
| ML18153B101 | |
| Person / Time | |
|---|---|
| Site: | Surry, North Anna  |
| Issue date: | 10/11/1994 |
| From: | Ohanlon J VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| REF-GTECI-A-46, REF-GTECI-SC, TASK-A-46, TASK-OR 94-422, GL-87-02, GL-87-2, GL-88-20, NUDOCS 9410180186 | |
| Download: ML18153B101 (3) | |
Text
e e
VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND? VIRGINIA 23261 October 11, 1994 United States Nuclear Regulatory Commission Attention: Document Control Desk Washington, D. C. 20555 Gentlemen:
VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNITS 1 AND 2 Serial No.94-422 NL&P/ETS Docket Nos. 50-280 50-281 50-338 50-339 License Nos. DPR-32 DPR-37 NPF-4 NPF-7 NORTH ANNA POWER STATION UNITS 1 AND 2 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 87-02 STATUS AND SCHEDULES FOR UNRESOLVED SAFETY ISSUE (USI) A-46. SUPPLEMENT 1 TO GENERIC LETTER 87-02 AND FOR INDIVIDUAL PLANT EXAMINATION OF EXTERNAL EVENTS (IPEEE)-SEISMIC. GENERIC LETTER 88-20, SUPPLEMENT 4 In our 120-day response Serial No.92-384, dated September 18, 1992, to Supplemental Safety Evaluation Report Number 2 (SSER-2) on Revision 2 of the Generic Implementation Procedure (GIP), we provided our commitment to use the methodology developed in the GIP with exceptions identified in SSER-2 to resolve the USI A-46 issue. That letter also identified the completion dates for plant walkdowns and the schedule for submittal of USI A-46 summary reports for North Anna Power Station and Surry Power Station. The schedule for the submittal of IPEEE (Seismic) reports was also provided. In your Safety Evaluation Report (SER) dated November 20, 1992, you accepted our methodologies and schedules for both the USI A-46 and the IPEEE (Seismic) programs. This letter provides a brief summary of the current
- status of these programs and identifies changes in the completion schedules and submittal of reports.
Implementation of the two programs is proceeding at both North Anna and Surry in accordance with the agreed methodologies and significant milestones have been completed consistent with the initial schedule. As indicated in our 120-day response, our approach integrates the walkdowns and analytical evaluations for the USI A-46 and IPEEE (Seismic) programs as much as practicable in order to avoid unnecessary and costly duplication. Consistent with the accepted methodologies, Safe Shutdown Equipment Lists (SSELs) and seismic in-structure response spectra for both programs have been developed, most of the relay evaluation effort has been completed, and seismic walkdowns have been performed for 55% of the equipment (about 1700 components of 3100 component) on the SSELs at the two stations. Following the I walkdowns, analytical calculations, e.g., anchorage, seismic fragility, seismic capacity and other evaluations are being performed for several components, as necessary. A
\\ D
(
---94_1_0_1_8_0_1_8~
0 ~-~~1~--'-0-'----l :__,l -------
~DR ADOCK 05000280 PDR
e e
description of some of the findings resulting from this effort, which is considered to be represe.ntative of the entire scope, is provided below.
For the relay evaluation effort, the essential relays in the USI A-46 scope were determined to be seismically adequate at North Anna. At Surry, one low ruggedness relay model was discovered and is planned for replacement.
Seismic qualification data has not been located for a few essential relays and further testing and analysis is planned. For resolution of the Gl-57 issue within IPEEE, we have identified mercury relays in the Fire Protection System and are evaluating their seismic adequacy.
For the completed equipment walkdowns, only a few seismic concerns were identified.
The most significant concern was the discovery ofconditior,s w.here the. as-installe~
configuration was different than the as-designed, involving either missing welds or anchor bolts.
These conditions were reported as deviations and were promptly evaluated and corrected prior to unit start-up. Plant documentation was reviewed and it was determined that these concerns were isolated cases and not applicable to the corresponding components in the other unit. The effort accomplished to date does not address cable trays/conduit raceway review. However, cable tray evaluations have recently begun.
We consider that our resolution of design deviations or potentially significant seismic issues is an efficient approach to closing the overall generic issue as well as an enhancement in safety. Several of the simple physical modifications were made because this was the most efficient method to resolve a potential seismic outlier or a deviation rather than perform more detailed calculations to verify the adequacy of the existing conditions. Due to the simplicity and low cost of the modifications, it was decided that making simple modifications was the more cost effective method of resolution.
To date, we have completed more than 50% of the walkdowns at the two stations and have found no significant seismic concerns. In addition to the walkdown results to date, the following information supports the conclusion that the seismic risk at both Surry and North Anna is significantly less than generically considered:
(a) the program which was undertaken by the NRC and its consultants in NUREG-1150 for conducting Seismic Probabilistic Risk Assessment (SPRA) for Surry did not identify any safety concerns, (b) the revised Livermore Seismic Hazard Estimates contained in NUREG-1488 indicate that the mean seismic hazard at SPS and NAPS is lower than the previous Livermore estimate, (c) the Conservative Design and Hazard in-structure seismic spectra for the USI A-46 and IPEEE (Seismic) programs respectively at Surry Power Station have relatively low amplifications for all structures, and (d) several components in the SSELs are qualified to the newer industry standards, e.g., IEEE Standard 344-1975 in lieu of IEEE 344-1971. Based on the walkdown and evaluation results to date and the seismic risk information, we believe the USI A-46 and IPEEE programs to be of marginal safety benefit.
Consistent with the plan stated in our 120-day response letter, the major portion of the USI A-46 and IPEEE (Seismic) effort is being performed with trained, in-house engineers. This has proven to be a cost effective approach, and has exceeded our expectation of the value of developing hands-on knowledge of the plant by our in-house seismic engineers. However, to meet the schedules stated in our 120-day letter, substantial assistance from outside consultants would be required. By delaying the completion and submittal schedules, an even larger part of the A-46 and IPEEE
e e
(Seismic) effort could be performed with Company engineers, and potentially save costs.ir. excess of the Cost Beneficial Licensing Action threshold for each Station.
Additionally, this approach will be very beneficial to us in that our engineers will be directly involved in almost the entire effort and will obtain first-hand insights into plant specific seismic vulnerabilities, if any. Given the satisfactory results of the effort to date, a delay in the schedule is not considered to be safety significant. Furthermore, recent studies establish a lower seismic risk than previously thought, further reinforcing the minimal safety significance of a scheduling delay. We believe that a delay in completion schedule is justified and consistent with CBLA criteria. Therefore,
- we are revising our completion and submittal schedules for these programs as follows:
North Anna Power Station Surry Power Station IPEEE (Seismic)
February 1997 August 1997 US1A46 May 1997 November 1997 Should you have any questions or require additional information, please contact us.
Very truly yours,
~?.~
James P. O'Hanlon Senior Vice President - Nuclear cc:
U. S. Nuclear Regulatory Commission Region II 101 Marietta Street, N. W.
Suite 2900 Atlanta, Georgia 30323 Mr. Eugene V. lmbro, Director Regulatory Review Group/CBLA Programs United States Nuclear Regulatory Commission Washington, D. C. 20555 Mr. M. W. Branch NRC Senior Resident Inspector Surry Power Station Mr. R. D. McWhorter NRC Senior Resident Inspector North Anna Power Station