ML18153C795
| ML18153C795 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 10/28/1991 |
| From: | Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 91-134B, NUDOCS 9111040195 | |
| Download: ML18153C795 (4) | |
Text
e VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 October 28, 1991 United States Nuclear Regulatory Commission Attention: Document Control Desk Washington, D. C. 20555 Gentlemen:
VIRGINIA ELECTRIC AND POWER COMPANY Serial No.
NL&P/CGL Docket Nos.
License Nos.
SURRY POWER STATION UNITS 1 AND 2 SUPPLEMENTAL INFORMATION ON SURRY INDIVIDUAL PLANT EXAMINATION / INTERNAL FLOODING ANALYSIS 91-1348 R2 50-280 50-281 DPR-32 DPR-37 Virginia Electric and Power Company transmitted the Individual Plant Examination (IPE) results for Surry Power Station in an August 30, 1991 letter (Serial No. 91-134A).
The transmittal letter included identification of the activities planned to eliminate the vulnerability to internal flooding and the scheduled implementation dates.
On October 9, 1991, Virginia Electric and Power Company personnel met with the NRC to present the methodology used in performing the Surry IPE and the results of the IPE. It was mentioned during the meeting that the schedule for some of the planned modifications were still under review and should be able to be improved. We have now completed the review of the original schedule and have identified the items that can be accomplished sooner. The attachment summarizes our previously commited dates, as well as the accelerated dates.
As discussed during a subsequent October 23, 1991 meeting, Virginia Electric and Power Company agreed to reanalyze the Surry internal flooding analysis.
The purpose of this reanalysis is to better quantify the conservatism in our August 30, 1991 submittal.
This reanalysis is scheduled for completion by November 22, 1991.
Specifically, the reanalysis will consider more realistic treatment of component failure mechanisms and associated leak rates.
In the current analysis, the postulated mechanism for large breaks in valves and pipes is water hammer resulting from rapid closure of one of the circulating water or service water system valves. The original analysis assumes that any water hammer event will result in component failure. This is overly conservative in that it does not address actual component material strength or system response.
Therefore, the current analysis provides a conservative upper bound estimate. The approach to be used in the reanalysis will involve detailed examination of the following aspects:
jot{
r '\\ \\
frequency and resultant pressure profile of water hammer events, the stresses and associated material responses in valve bodies, pipes, and expansion joints due to water hammer events deterministic consideration of weak link failure and subsequent pressure relieving capability, and determination of spectrum break sizes and associated flow rates.
We would like to meet with you prior to November 22, 1991 to discuss the results of our reanalysis, as well as any additional proposed enhancements to further minimize both the probability and consequences of an internal flooding event.
In the interim, Virginia Electric and Power Company will augment the present shift coverage of potential flood areas with a dedicated flood watch for those areas. The dedicated flood watch would specifically be observing internal flood-important valves, pipe, and expansion joints on a continuous basis for early indications of leakage or other degraded performance. Furthermore, as an enhancement to flood mitigation capabilities, administrative controls will be added, on an interim basis, to require operability of all the nine sump pumps to further increase expected availability. In the event of a sump pump being inoperable, priority will be given to prompt restoration of the pump to an operable condition. Finally, procedures for installation of stop logs at the high level intake will be formalized and the resources (both material and personnel) required for installation will be identified and dedicated to ensure the most timely action possible in use of stop logs for flood mitigation.
If you have questions regarding this transmittal, please contact us.
Very truly yours,
~L~
W. L. Stewart Senior Vice President - Nuclear Attachment - Planned Modifications/Schedule to Eliminate Surry Vulnerability to Internal Flooding
cc:
U. S. Nuclear Regulatory Commission Region II 101 Marietta Street, N. W.
Suite 2900 Atlanta, Georgia 30323 Mr. M. W. Branch NRC Senior Resident Inspector Surry Power Station
ATTACHMENT PLANNED MODIFICATIONS/SCHEDULE TO ELIMINATE SURRY VULNERABILITY TO INTERNAL FLOODING Commitment Procedure Revisions for Response to Flooding in TB, MER 3, Safeguards Building, and Auxiliary Building During Power Operation Improved Sump Pump Reliability -
Maintain at Least 7 Pumps Operable at All Times Date from 91-134A Complete Procedure Revisions for Isolation of 12/31 /91 CW and SW Piping for Maintenance During Outages Development of Expansion Joint 12/31 /92 Inspection Program and Service Life Replacement Program Development of Inspection Program 12/31 /92 for Valves (e.g., bolts, connecting pins)
Development of TB Sump Pump Reliability 12/31 /92 Program (e.g., operability requirements, surveillance and PM programs)
Inspections and Maintenance During Outages Installation of Backflow Prevention Devices 12/31 /95 in Charging Pump Drain Lines Installation of Submersible Operators for 12/31 /95 BC/CC MOVs Relocation of Power Source for Existing 12/31 /95 TB Sump Pumps Accelerated Date Complete Ongoing No Change To Support 2/92 U1 and 2/93 U2 Outages To Support 2/92 U1 and 2/93 U2 Outages To Support 2/92 U1 and 2/93 U2 Outages During 2/92 U1 and 2/93 U2 Outages 6/30/92 No Change No Change