ML18153D016
| ML18153D016 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 05/27/1992 |
| From: | Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 92-299, NUDOCS 9206010089 | |
| Download: ML18153D016 (10) | |
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VIRGINIA ELECTRIC AND POWER COMPANY R1c1IMOND, VIRGINIA 23261 May 27, 1992 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 STATUS OF MODIFICATIONS AND ACTIVITIES ASSOCIATED WITH INTERNAL FLOODING Serial No.
NL&P/CGL Docket Nos.
License Nos.92-299 R3 50-280 50-281 DPR-32 DPR-37 The NRC's Assessment of Plant Internal Flooding Vulnerability for the Surry Power Station was issued on April 21, 1992. In your assessment, you indicate that our plans for resolving this issue should be submitted by May 1992. The purpose of this letter is to advise you of our ongoing evaluation of proposed long term modifications and the status of these activities.
Discussion of the ongoing evaluation is provided in. Attachment 1 also includes a table identifying a preliminary estimate of the core damage frequency (CDF) reduction associated with each of the options being evaluated. We plan to have a conceptual design report, including cost and schedule, prepared for these options by September 1992 for internal review. We will advise you of the conclusions of the conceptual design report and our intended actions following completion of this review. It is our intent to incorporate those long term modifications, which are feasible and cost effective, into the Surry design to resolve the internal flooding vulnerability issue.
In addition, on December 19, 1991, we indicated that in approximately six months we would advise you of the status of the modifications and activities associated with internal flooding. This letter provides an updated status. Attachment 2 lists the modifications and activities identified in our letters of November 26, 1991 (Serial No.
91-134D) and December 19, 1991 (Serial No. 91-134E). Attachment 3 discusses the items involving a completed evaluation or assessment, other than the evaluation of the proposed long term modifications discussed in Attachment 1.
Very truly yours, Ml)~
W. L. Stewart Senior Vice President - Nuclear Attachments (3)
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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 1 ONGOING EVALUATION OF PROPOSED LONG TERM MODIFICATIONS Evaluation of Modifications to Seal Plates for Insertion against Flow Relative to the option of isolation of a potential flood source at the intake structure, five suboptions are being evaluated.
These suboptions include the following modifications:
The placement of a single flood gate to be lowered immediately upstream of each 96 inch diameter circulating water pipe entrance on the downstream side of the High Level Intake Structure (Option 1 A). This flood gate could be either a sliding mechanical flood gate or a lowered flood gate.
The placement of a two panel flood gate to be lowered downstream of the existing trash rack and upstream of the traveling water screens (Option 18).
The placement of a four panel flood gate upstream of the trash racks (similar to the existing seal plates and in the same position, but equipped with low friction bearing type rollers) (Option 1 C).
The placement of a single flood gate to be lowered upstream of each trash rack.
Each flood gate will be equipped with low friction rollers (Option 1 D).
The permanent installation of a 96 inch diameter valve at each of the circulating water pipe openings at the north end of the High Level Intake Structure (Option 1 E).
Evaluation of Increasing the Height of Dikes at the Auxiliary Building Pipe Tunnel This evaluation considers the installation of a 6 foot steel dike (replacing the current 2 foot dike) to prevent flow of Turbine Building flood water from entering the Auxiliary Building (Option 2).
Evaluation of Installation of a Water Tight Door Between the Emergency Switchgear Room Opening and the Turbine Building This evaluation considers the installation of a water tight double door between the Emergency Switchgear Room and the Turbine Building.
This modification would prevent Turbine Building floods from entering the Emergency Switchgear Room until the water level reaches at least 6 feet on the Turbine Building floor (Option 3).
ATTACHMENT 1 (continued)
Evaluation of Installation of a Water Tight Door Between MER-3 and the Emergency Switchgear Room This evaluation considers the installation of a water tight door at MER-3 to prevent floods originating in MER-3 from propagating to the Emergency Switchgear Room (Option 4).
ATTACHMENT 1 (continued)
PRELIMINARY EVALUATION OF PROPOSED LONG TERM MODIFICATIONS TO REDUCE THE VULNERABILITY TO INTERNAL FLOODS AT SURRY Option Base Options
- 1. Modification at High Level Intake Structure
- 2. Increased Height of the Dike at the Auxiliary Building Tunnel to 6 Feet
- 3. ESR Water Tight Door
1 (t<60 min) 1 (t>60 min) 1, 2, 3 (t<30 min) 1, 2, 3 (30<t<120 min) 4 (t not applicable) 1, 2, 3, 4 (t<30 min) 1, 2, 3, 4 (30<t<120 min) 1&4 (t<60 min) 1.6E-5 3.5E-5 Insignificant 5.1 E-5 1.9E-5 3.2E-5 1.SE-5 3.5E-5 2.8E-5 2.3E-5 4.7E-5 3.7E-6 4.4E-5 6.7E-6 4.4E-5 6.7E-6 t = the time from flood initiation to isolation at the High Level Intake Structure Transmitted to the NRC by letter Serial No. 91-134D, dated 11/26/91.
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ATTACHMENT 2 STATUS OF ADDITIONAL PLANNED MODIFICATIONS AND ACTIVITIES ASSOCIATED WITH INTERNAL FLOODING VIRGINIA POWER LETTER SERIAL NO. 91-134D, NOVEMBER 26, 1991 Modification or Activity Procedure Revisions for Response to Flooding (i.e., abnormal and annunciator response procedures) in TB, MER 3, Safeguards Building, and Auxiliary Building During Power Operation Procedure Revisions for Isolation of CW and SW Piping for Maintenance During Outages Implementation of EWR to Improve Flood Control Panel and Enhance Annunciation Installation of Backflow Prevention Devices in Charging Pump Cubicle Drain Lines Repair/Replacement of Certain Backflow Prevention Devices Flow Shield Installation on Expansion Joints in Service Water Supply Lines for Bearing Cooling and Component Cooling (at BC/CC MOVs)
Communication of Importance of Flood Protection Program to Station Personnel Procedure Revisions for CW Maintenance (i.e., double isolation, tagouts, flood watch during maintenance, slow refilling of CW lines prior to stop log removal)
Improved Sump Pump Reliability - Maintain at Least 7 Pumps Operable at All Times Stop Log Staging, Procedures, and Assigned Personnel and Equipment in Place Internal and External Inspection of a 96" Expansion Joint, External Inspection of the Bearing Cooling Expansion Joints, and Evaluation of Inspection Results Restoration of Existing Expansion Joint Shields Status or Schedule Complete Complete Complete Complete Complete Complete Complete Complete Ongoing Ongoing Complete Complete
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ATTACHMENT 2 (continued)
Development of Turbine Building Sump Pump Operation Rotational Schedule (within Existing Design)
Development of Turbine Building Sump Pump Test Procedure (including level switches, check valves, pump flow testing)
Completion of Initial Performance of Turbine Building Sump Pumps Special Test to Establish Baseline for All Pumps Evaluation of Insertion of Stop Logs during CW/SW Maintenance Activities Reassessment of CW and SW Piping Inspection Schedules Performance of Heavy Load Evaluation Using NUREG-0612 as a Guideline Review of Annual PM Procedures for Flood Protection Devices and Schedule Modification of CW MOV Locking Pins Such That Full Engagement into Valve Stem is Easily Discernable Revision of Refueling Procedures for Testing Flood Protection and Alarm Systems Development/Documentation of Expansion Joint Inspection Program and Service Life Replacement Program Development/Documentation of Inspection Program for Valves (e.g., bolts, connecting pins, and manual operators)
Development/Documentation of TB Sump Pump Reliability Program (e.g., operability requirements, surveillance and PM programs)
Replacement of Certain Expansion Joints Eight Intermediate Outlet EJs rescheduled as separate line item (Serial 91-134E)
SW EJs tied to outage: #42, 43, 46, 48, 50 & 52 for both units Assessment of the Need for a Flood Mitigation Equipment Reliability Program Assessment of the Need for Procedures Validation of Operator Actions for Flood Mitigation Complete Complete Complete Complete Complete Complete Complete Complete Complete Complete U 1 Complete and To Support 2/93 U2 Outage
ATTACHMENT 2 (continued)
Assessment of Installation of Submersible Operators for BC/CC MOVs Relocation of Power Source for Existing TB Sump Pumps 12/31/92 12/31/93 VIRGINIA POWER LETIER SERIAL NO. 91-134E, DECEMBER 19, 1991 Status or Modification or Activity Schedule Evaluation of Oconee Modifications for Internal Flooding for Applicability to Surry As an Interim Measure, Inspection of Condenser Intermediate Outlet Complete Expansion Joints (eight EJs) and Installation of Reduced Gap Flow Shields Replacement of Condenser Intermediate Outlet Expansion Joints Complete on Units 1 and 2 Evaluation of Modifications to Seal Plates for Insertion Against Flow Evaluation of Increasing the Height of Dikes at the Auxiliary Building Pipe Tunnel and the Turbine Building Emergency Switchgear Room Door Evaluation of Installation of a Water Tight Door at the MER 3 -
Emergency Switchgear Room Opening Evaluation of the Installation of Permanent Reduced Gap Flow Complete Shields on Expansion Joints Reassessment of the Internal Flooding Design Basis and Update of 7/1/92 UFSAR, as Necessary
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e ATTACHMENT 3
SUMMARY
OF CONCLUSIONS OF EVALUATIONS OR ASSESSMENTS ASSOCIATED WITH INTERNAL FLOODING Evaluation of Insertion of Stop Logs during CW/SW Maintenance Activities This evaluation considered when double isolation (not necessarily stop logs) should be utilized during CW/SW maintenance activities. The conclusion was that the use of double isolation should be encouraged wherever possible to minimize the potential flooding risk during maintenance.
Maintenance operating procedures and an operational checklist have been revised to emphasize this preference for double isolation.
Reassessment of CW and SW Piping Inspection Schedules This assessment considered techniques, frequency, and acceptance criteria for coating and corrosion inspection to assure integrity of the CW/SW system piping. The scope of CW and SW lines to be inspected is based on the flood sources which could exceed the critical flood flow rate identified in the Surry IPE. Procedures addressing inspection of this scope will be written to support the next Unit 2 outage, which is currently scheduled for February 1993. The frequency of the required inspections will be based on inspection trends rather than on results of single inspections. Note that the scope of existing procedures regarding service water system inspection and maintenance will be expanded beyond the fouling and corrosion mitigation scope for the safety related portions of the SW system now being addressed for Generic Letter 89-13.
Assessment of the Need for a Flood Mitigation Equipment Reliability Program The conclusion of this assessment was that performance of a Reliability Centered Maintenance (ACM) evaluation relative to the Surry !PE/internal flooding analysis is not appropriate. Instead, a more appropriate approach, which will be undertaken, is to develop a preventive maintenance plan for affected components that were not previously included in the ACM studies on the CW and SW systems.
Affected components requiring preventive maintenance actions will be identified during June 1992.
Assessment of the Need for Procedures Validation of Operator Actions for Flood Mitigation This assessment was a commitment made in response to a NRC reviewer's question with regard to operator safety while taking manual actions in response to an internal flood. The various actions taken credit for in the Surry IPE, along with the procedures requiring those actions, were reviewed. The procedures including these actions had been validated as part of the procedure preparation/revision process pursuant to the requirements of VPAP-0502, entitled "Procedure Process Control." It was determined that no further procedure validation of flood mitigation operator actions is required to assure operator safety.
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ATTACHMENT 3 (continued) e Evaluation of Oconee Modifications for Internal Flooding for Applicability to Surry The Oconee modifications for internal flooding were reviewed for applicability to Surry as part of the preparation of the IPE. It was determined that a large diameter drain as used at Oconee was not practical for Surry. Due to the low elevation of the Turbine Building basement, a drain would have to go around the station to get from the Turbine Building to the discharge canal.