ML18153D368

Forwards Addl Info Re Internal Flooding Mods & Activities, Per NRC 930414 Telcon Request

ML18153D368
Person / Time
Site:	Surry
Issue date:	06/21/1993
From:	Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
93-163A, NUDOCS 9306290249
Download: ML18153D368 (9)

Text

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VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 June 21, 1993 United States Nuclear Regulatory Commission Attention: Document Control Desk Washington, D. C. 20555 Serial No.

NL&P/CGL Docket Nos.

93-163A R3" 50-280 50-281 License Nos. DPR-32 Gentlemen:

VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNITS 1 AND 2 ADDITIONAL INFORMATION REGARDING INTERNAL FLOODING DPR-37 During an April 14, 1993 telephone conversation between Mr. H. N. Berkow of the NRC and Mr. M. L. Bowling of Virginia Power, the NRC requested additional information regarding some of the modifications and activities we have undertaken to address the issue of internal flooding at Surry Power Station.

Specifically, the requested information is:

Description of expansion joint inspection and replacement activities, Discussion of the operational objectives of the modified seal plates, Discussion of the plan associated with submersible operators, and Update of the list of modifications and activities, last transmitted to the NRC in our May 27, 1992 letter (Serial No.92-299).

This information is provided in the attachments.

Very truly yours, rJl~

W. L. Stewart Senior Vice President - Nuclear Attachments:

1. Additional Information Regarding Internal Flooding Modifications and Activities

2. Status of Additional Planned Modifications and Activities Associated with Internal Flooding r---* 9306290249 930621 IT' 1

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e 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

I ATTACHMENT 1 ADDITIONAL INFORMATION REGARDING INTERNAL FLOODING MODIFICATIONS AND ACTIVITIES Description of Expansion Joint Inspection and Service Life Replacement Activities As stated in our April 12, 1993 letter (Serial No.93-163), expansion joint inspection and service life replacement activities have been implemented to maintain expansion joint adequacy. These activities have been instituted by means of a mechanical maintenance procedure and model work orders.

The current expansion joint inspection activity includes:

visual inspection of expansion joint retaining hardware for pipe anchor and flange support integrity, visual inspection of expansion joint exterior surfaces for flange base cracking, flange leakage, cover cracks, and overall surface condition (soft spots, bulging, sponginess), and visual inspection of expansion joint to flange alignment for angular misalignment, lateral misalignment, and torsional misalignment.

The expansion joint inspection activity is conducted either during refueling or during other periods of sufficient duration without operational restrictions. The inspection process includes manufacturer recommendations, operational experience, and engineering judgment.

Expansion joint service life replacement is determined based on the expansion joint application, inspection results, operational experience, and engineering evaluation.

As stated in Section 3.4.4 of the Surry Internal Flooding Reanalysis transmitted by our November 26, 1991 letter (Serial No. 91-234D), "normal life expectancy for the type of rubber expansion joints in use at Surry is at least 8 years. With careful installation and proper material selection, reliable service can be assumed for 1 Oto 12 years."

The expansion joints currently included in the inspection and replacement activities are:

the circulating water (CW) system condenser inlet, intermediate outlet, and outlet expansion joints, the expansion joints in the service water (SW) system supply lines to the bearing cooling and component cooling heat exchangers, and the expansion joints at the inlets and outlets of the bearing cooling and component cooling heat exchangers.

ATTACHMENT 1 (continued)

This discussion provides a description of the inspection and replacement activities as they are currently configured.

We intend to use the experience gained from inspections to adjust and improve the inspection requirements and frequencies of inspection and replacement. Any future changes to the inspection and replacement activities will be made based on engineering evaluation and by review by the Station Nuclear Safety and Operating Committee (SNSOC), as appropriate.

Discussion of the Operational Objectives of the Modified Seal Plates As indicated in our October 30, 1992 letter (Serial No. 92-299A), there was no high level intake structure isolation option with a cost commensurate with the associated reduction in core damage frequency (CDF). Therefore, high level intake structure isolation is being pursued as a plant design enhancement. Our April 12, 1993 letter identified a modified seal plate arrangement, which will enhance our ability to insert the seal plates for flood mitigation, as the alternative selected for the high level intake structure isolation. Also as noted in our April 12, 1993 letter, the modified seal plate arrangement involves the addition of rollers to the existing seal plates to help eliminate the potential problem of the panels binding in their guides during installation. In our September 3, 1992 letter (Serial No. 91-134H), we indicated that a seal plate insertion time of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> could be accomplished for long term isolable floods* with the continued prestaging of equipment and material required to insert the seal plates.

Our September 3, 1992 letter also indicated that we are using administrative controls for personnel availability. The administrative controls use personnel on site and, if required, personnel will be called in.

With the arrangements in place for equipment/material/personnel availability, it is anticipated that seal plate insertion could be initiated within approximately 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> under optimum circumstances. The enhancement will facilitate the insertion of the modified seal plates within the 24-hour time frame. Furthermore, review of the modified seal plate design confirms the ability to insert the seal plates against flow rates larger than the critical flood flow rate**.

Long term isolable floods are defined in Appendix E of the Surry !PE/Internal Flooding Analysis (Serial No. 91-134A, dated August 30, 1991) as "those which occur due to breaks in the condenser inlet piping upstream of the inlet valve, or in one of the inlet valves themselves, and can therefore only be isolated by installing stop logs. Isolation is assumed to occur 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> after initiation of the flood."

• • Critical flood flow rate of 10,100 gpm is defined in the Surry Internal Flooding Reanalysis (Serial No. 91-134D, dated November 26, 1991) as "the minimum rate that is capable of causing damage in the switchgear room given 7 of 9 sump pumps (operating) and seal plate installation within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />."

e ATTACHMENT 1 (continued)

Discussion of the Plan Associated with Submersible MOV Operators As indicated in our April 12, 1993 letter, we plan to:

1) initiate motor operated valve (MOV) operator modifications for submersible service on the 8 (4 per unit) circulating water inlet valves following the recently completed Unit 2 refueling outage. It is anticipated that these modifications will be completed by the end of the next Units 1 and 2 refueling outages, currently scheduled for 1994.

2) evaluate other valves (i.e., valves in the turbine building valve pits in the SW system supply lines to the bearing cooling (BC) and component cooling (CC) heat exchangers) for modification following completion of the CW inlet valve modifications.

From an IPE/internal flooding perspective, the CW inlet valves and the valves in the SW system supply lines (in the valve pits) to the BC and CC heat exchangers are the MOVs of interest relative to the potential inability to isolate a flood source due to splashing or submersion.

Our November 26, 1991 letter (Serial No. 91-1340) concluded in Enclosure 2 that spraying of a CW inlet valve during a flooding event will not affect its operability and the valve will close before being submerged. Although spraying or submergence of the CW inlet valves is not a concern, we plan to modify these valves as a design enhancement.

Relative to the MOVs in the SW supply lines (in the valve pits) to the BC and CC heat exchangers, our August 30, 1991 letter (Serial No. 91-134A) indicated that we planned to install submersible operators on these valves by December 31, 1995.

Subsequently, in our October 29, 1991 letter, we stated that we would instead install flow shields on the expansion joints in the SW supply lines (in the valve pits) to the BC and CC heat exchangers to reduce the flow rate which could occur upon failure of the expansion joints to less than the dewatering capacity of the sump pumps.

Subsequently, these SW supply line flow shields were installed. Consequently, our November 26, 1991 letter (Serial No. 91-1340) reflected that we would assess the need for installation of submersible operators for the MOVs in the SW supply lines (in the valve pits) to the BC and CC heat exchangers. The installation of these SW supply line flow shields results in approximately the same CDF reduction as MOV operators qualified for submersible service in the SW supply lines (in the valve pits) to the BC and CC heat exchangers. Therefore, either flow shields on the expansion joints or MOV operators qualified for submersible service are acceptable options for the SW supply lines (in the valve pits) to the BC and CC heat exchangers. We will assess these options and determine the preferred alternative, but do not plan to do both. A factor in this determination will be the operational experience gained from the modification of the CW inlet valves for submersible service.

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 Status or Schedule Complete Complete Complete Complete Complete Complete Complete Complete Ongoing Ongoing Complete

ATTACHMENT 2 (continued)

Restoration of Existing Expansion Joint Shields 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 SW EJs tied to outage: #42, 43, 46, 48, 50 & 52 for both units Eight Intermediate Outlet EJs rescheduled as separate line item (Serial 91-134E)

Complete Complete Complete Complete of 92-299, 5/27/92 of 92-299, 5/27/92 Complete Complete Complete Complete Complete Complete Complete U 1-Complete U2-Complete

ATTACHMENT 2 (continued)

Assessment of the Need for a Flood Mitigation Equipment Reliability Program Assessment of the Need for Procedures Validation of Operator Actions for Flood Mitigation Assessment of Installation of Submersible Operators for MOVs in the SW Supply Lines to Bearing Cooling and Component Cooling Heat Exchangers Relocation of Power Source for Existing TB Sump Pumps of 92-299, 5/27/92 of 92-299, 5/27/92 93-163, 4/12/93 93-163A, 6/21/93 of 92-299A, 1 0/30/92 VIRGINIA POWER LETTER SERIAL NO. 91-134E, DECEMBER 19, 1991 Status or Modification or Activity Schedule Evaluation of Oconee Modifications for Internal Flooding for of Applicability to Surry 92-299, 5/27/92 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 of Flow 92-299, 5/27/92 Evaluation of Increasing the Height of Dikes at the Auxiliary Building Pipe Tunnel and the Turbine Building Emergency Switchgear of Room Door 92-299, 5/27/92 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 Shields on Expansion Joints Reassessment of the Internal Flooding Design Basis and Update of UFSAR, as Necessary of 92-299, 5/27/92 93-163, 4/12/93 Complete

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ATTACHMENT 2 (continued)

VIRGINIA POWER LETTER SERIAL NO.93-163, APRIL 12, 1993 Status or Long Term Modification Schedule Installation of Watertight Door at MER 3 Entrance from ESGR 12/31/93 Modified Seal Plate Arrangement for High Level Intake Structure 12/31/94 Isolation Modification of CW Inlet MOV Operators for Submersible Service Unit 1 By end of next U1 RFO.

Unit 2 By end of next U2 RFO.

Removal of Reduced Gap Flow Shields on the Condenser To be determined.

Intermediate Outlet Discharge Expansion Joints VIRGINIA POWER LETTER SERIAL NO. 93-163A, JUNE 21, 1993 Long Term Modification Determination of Preferred Option on SW Supply Lines to BC and CC Heat Exchangers: EJ Flow Shields versus Submersible MOV Operators Status or Schedule To be determined.